37.2: How Hormones Work
Skills to Develop
- Explain how hormones work
- Discuss the role of different types of hormone receptors
Hormones mediate changes in target cells by binding to specific hormone receptors . In this way, even though hormones circulate throughout the body and come into contact with many different cell types, they only affect cells that possess the necessary receptors. Receptors for a specific hormone may be found on many different cells or may be limited to a small number of specialized cells. For example, thyroid hormones act on many different tissue types, stimulating metabolic activity throughout the body. Cells can have many receptors for the same hormone but often also possess receptors for different types of hormones. The number of receptors that respond to a hormone determines the cell’s sensitivity to that hormone, and the resulting cellular response. Additionally, the number of receptors that respond to a hormone can change over time, resulting in increased or decreased cell sensitivity. In up-regulation , the number of receptors increases in response to rising hormone levels, making the cell more sensitive to the hormone and allowing for more cellular activity. When the number of receptors decreases in response to rising hormone levels, called down-regulation , cellular activity is reduced.
Receptor binding alters cellular activity and results in an increase or decrease in normal body processes. Depending on the location of the protein receptor on the target cell and the chemical structure of the hormone, hormones can mediate changes directly by binding to intracellular hormone receptors and modulating gene transcription, or indirectly by binding to cell surface receptors and stimulating signaling pathways.
Intracellular Hormone Receptors
Lipid-derived (soluble) hormones such as steroid hormones diffuse across the membranes of the endocrine cell. Once outside the cell, they bind to transport proteins that keep them soluble in the bloodstream. At the target cell, the hormones are released from the carrier protein and diffuse across the lipid bilayer of the plasma membrane of cells. The steroid hormones pass through the plasma membrane of a target cell and adhere to intracellular receptors residing in the cytoplasm or in the nucleus. The cell signaling pathways induced by the steroid hormones regulate specific genes on the cell's DNA. The hormones and receptor complex act as transcription regulators by increasing or decreasing the synthesis of mRNA molecules of specific genes. This, in turn, determines the amount of corresponding protein that is synthesized by altering gene expression. This protein can be used either to change the structure of the cell or to produce enzymes that catalyze chemical reactions. In this way, the steroid hormone regulates specific cell processes as illustrated in Figure \(\PageIndex{1}\).
Exercise \(\PageIndex{1}\)
Heat shock proteins (HSP) are so named because they help refold misfolded proteins. In response to increased temperature (a “heat shock”), heat shock proteins are activated by release from the NR/HSP complex. At the same time, transcription of HSP genes is activated. Why do you think the cell responds to a heat shock by increasing the activity of proteins that help refold misfolded proteins?
- Answer
-
Proteins unfold, or denature, at higher temperatures.
Other lipid-soluble hormones that are not steroid hormones, such as vitamin D and thyroxine, have receptors located in the nucleus. The hormones diffuse across both the plasma membrane and the nuclear envelope, then bind to receptors in the nucleus. The hormone-receptor complex stimulates transcription of specific genes.
Plasma Membrane Hormone Receptors
Amino acid derived hormones and polypeptide hormones are not lipid-derived (lipid-soluble) and therefore cannot diffuse through the plasma membrane of cells. Lipid insoluble hormones bind to receptors on the outer surface of the plasma membrane, via plasma membrane hormone receptors . Unlike steroid hormones, lipid insoluble hormones do not directly affect the target cell because they cannot enter the cell and act directly on DNA. Binding of these hormones to a cell surface receptor results in activation of a signaling pathway; this triggers intracellular activity and carries out the specific effects associated with the hormone. In this way, nothing passes through the cell membrane; the hormone that binds at the surface remains at the surface of the cell while the intracellular product remains inside the cell. The hormone that initiates the signaling pathway is called a first messenger , which activates a second messenger in the cytoplasm, as illustrated in Figure \(\PageIndex{2}\).
One very important second messenger is cyclic AMP (cAMP). When a hormone binds to its membrane receptor, a G-protein that is associated with the receptor is activated; G-proteins are proteins separate from receptors that are found in the cell membrane. When a hormone is not bound to the receptor, the G-protein is inactive and is bound to guanosine diphosphate, or GDP. When a hormone binds to the receptor, the G-protein is activated by binding guanosine triphosphate, or GTP, in place of GDP. After binding, GTP is hydrolysed by the G-protein into GDP and becomes inactive.
The activated G-protein in turn activates a membrane-bound enzyme called adenylyl cyclase . Adenylyl cyclase catalyzes the conversion of ATP to cAMP. cAMP, in turn, activates a group of proteins called protein kinases, which transfer a phosphate group from ATP to a substrate molecule in a process called phosphorylation. The phosphorylation of a substrate molecule changes its structural orientation, thereby activating it. These activated molecules can then mediate changes in cellular processes.
The effect of a hormone is amplified as the signaling pathway progresses. The binding of a hormone at a single receptor causes the activation of many G-proteins, which activates adenylyl cyclase. Each molecule of adenylyl cyclase then triggers the formation of many molecules of cAMP. Further amplification occurs as protein kinases, once activated by cAMP, can catalyze many reactions. In this way, a small amount of hormone can trigger the formation of a large amount of cellular product. To stop hormone activity, cAMP is deactivated by the cytoplasmic enzyme phosphodiesterase , or PDE. PDE is always present in the cell and breaks down cAMP to control hormone activity, preventing overproduction of cellular products.
The specific response of a cell to a lipid insoluble hormone depends on the type of receptors that are present on the cell membrane and the substrate molecules present in the cell cytoplasm. Cellular responses to hormone binding of a receptor include altering membrane permeability and metabolic pathways, stimulating synthesis of proteins and enzymes, and activating hormone release.
Summary
Hormones cause cellular changes by binding to receptors on target cells. The number of receptors on a target cell can increase or decrease in response to hormone activity. Hormones can affect cells directly through intracellular hormone receptors or indirectly through plasma membrane hormone receptors.
Lipid-derived (soluble) hormones can enter the cell by diffusing across the plasma membrane and binding to DNA to regulate gene transcription and to change the cell’s activities by inducing production of proteins that affect, in general, the long-term structure and function of the cell. Lipid insoluble hormones bind to receptors on the plasma membrane surface and trigger a signaling pathway to change the cell’s activities by inducing production of various cell products that affect the cell in the short-term. The hormone is called a first messenger and the cellular component is called a second messenger. G-proteins activate the second messenger (cyclic AMP), triggering the cellular response. Response to hormone binding is amplified as the signaling pathway progresses. Cellular responses to hormones include the production of proteins and enzymes and altered membrane permeability.
Glossary
- adenylate cyclase
- an enzyme that catalyzes the conversion of ATP to cyclic AMP
- down-regulation
- a decrease in the number of hormone receptors in response to increased hormone levels
- first messenger
- the hormone that binds to a plasma membrane hormone receptor to trigger a signal transduction pathway
- G-protein
- a membrane protein activated by the hormone first messenger to activate formation of cyclic AMP
- hormone receptor
- the cellular protein that binds to a hormone
- intracellular hormone receptor
- a hormone receptor in the cytoplasm or nucleus of a cell
- phosphodiesterase (PDE)
- enzyme that deactivates cAMP, stopping hormone activity
- plasma membrane hormone receptor
- a hormone receptor on the surface of the plasma membrane of a cell
- up-regulation
- an increase in the number of hormone receptors in response to increased hormone levels


2.4: Some Interesting Facts about Division
- be able to recognize a whole number that is divisible by 2, 3, 4, 5, 6, 8, 9, or 10
Division by 2, 3, 4, and 5
A whole number is divisible by 2 if its last digit is 0, 2, 4, 6, or 8.
The numbers 80, 112, 64, 326, and 1,008 are all divisible by 2 since the last digit of each is 0, 2, 4, 6, or 8, respectively.
The numbers 85 and 731 are
not
divisible by 2.
A whole number is divisible by 3 if the sum of its digits is divisible by 3.
The number 432 is divisible by 3 since 4 + 3 + 2 = 9 and 9 is divisible by 3.
\(432 \div 3 = 144\)
The number 25 is not divisible by 3 since \(2 + 5 = 7\), and 7 is not divisible by 3.
A whole number is divisible by 4 if its last two digits form a number that is divisible by 4.
The number 31,048 is divisible by 4 since the last two digits, 4 and 8, form a number, 48, that is divisible by 4.
\(31048 \div 4 = 7262\)
The number 137 is not divisible by 4 since 37 is not divisible by 4.
A whole number is divisible by 5 if its last digit is 0 or 5.
The numbers 65, 110, 8,030, and 16,955 are each divisible by 5 since the last digit of each is 0 or 5.
Practice Set A
State which of the following whole numbers are divisible by 2, 3, 4, or 5. A number may be divisible by more than one number.
26
- Answer
-
2
Practice Set A
81
- Answer
-
3
Practice Set A
51
- Answer
-
3
Practice Set A
385
- Answer
-
5
Practice Set A
6,112
- Answer
-
2, 4
Practice Set A
470
- Answer
-
2, 5
Practice Set A
113,154
- Answer
-
2, 3
Division by 6, 8, 9, 10
A number is divisible by 6 if it is divisible by both 2 and 3.
The number 234 is divisible by 2 since its last digit is 4. It is also divisible by 3 since 2 + 3 + 4 = 9 and 9 is divisible by 3. Therefore, 234 is divisible by 6.
The number 6,532 is
not
divisible by 6. Although its last digit is 2, making it divisible by 2, the sum of its digits, 6 + 5 + 3 + 2 = 16, and 16 is not divisible by 3.
A whole number is divisible by 8 if its last three digits form a number that is divisible by 8.
The number 4,000 is divisible by 8 since 000 is divisible by 8.
The number 13,128 is divisible by 8 since 128 is divisible by 8.
The number 1,170 is
not
divisible by 8 since 170 is not divisible by 8.
A whole number is divisible by 9 if the sum of its digits is divisible by 9.
The number 702 is divisible by 9 since 7 + 0 + 2 is divisible by 9.
The number 6588 is divisible by 9 since 6 + 5 + 8 + 8 = 27 is divisible by 9.
The number 14,123 is
not
divisible by 9 since 1 + 4 + 1 + 2 + 3 = 11 is not divisible by 9.
A Whole number is divisible by 10 if its last digit is 0.
The numbers 30, 170, 16,240, and 865,000 are all divisible by 10.
Practice Set B
State which of the following whole numbers are divisible 6, 8, 9, or 10. Some numbers may be divisible by more than one number.
900
- Answer
-
6, 9, 10
Practice Set B
6,402
- Answer
-
6
Practice Set B
6,660
- Answer
-
6, 9, 10
Practice Set B
55,116
- Answer
-
6, 9
Exercises
For the following 30 problems, specify if the whole number is divisible by 2, 3, 4, 5, 6, 8, 9, or 10. Write "none" if the number is not divisible by any digit other than 1. Some numbers may be divisible by more than one number.
Exercise \(\PageIndex{1}\)
48
- Answer
-
2, 3, 4, 6, 8
Exercise \(\PageIndex{2}\)
85
Exercise \(\PageIndex{3}\)
30
- Answer
-
2, 3, 5, 6, 10
Exercise \(\PageIndex{4}\)
83
Exercise \(\PageIndex{5}\)
98
- Answer
-
2
Exercise \(\PageIndex{6}\)
972
Exercise \(\PageIndex{7}\)
892
- Answer
-
2, 4
Exercise \(\PageIndex{8}\)
676
Exercise \(\PageIndex{9}\)
903
- Answer
-
3
Exercise \(\PageIndex{10}\)
800
Exercise \(\PageIndex{11}\)
223
- Answer
-
none
Exercise \(\PageIndex{12}\)
836
Exercise \(\PageIndex{13}\)
665
- Answer
-
5
Exercise \(\PageIndex{14}\)
4,381
Exercise \(\PageIndex{15}\)
2,195
- Answer
-
5
Exercise \(\PageIndex{16}\)
2,544
Exercise \(\PageIndex{17}\)
5,172
- Answer
-
2, 3, 4, 6
Exercise \(\PageIndex{18}\)
1,307
Exercise \(\PageIndex{19}\)
1,050
- Answer
-
2, 3, 5, 6, 10
Exercise \(\PageIndex{20}\)
3,898
Exercise \(\PageIndex{21}\)
1,621
- Answer
-
none
Exercise \(\PageIndex{22}\)
27,808
Exercise \(\PageIndex{23}\)
45,764
- Answer
-
2, 4
Exercise \(\PageIndex{24}\)
49,198
Exercise \(\PageIndex{25}\)
296,122
- Answer
-
2
Exercise \(\PageIndex{26}\)
178,656
Exercise \(\PageIndex{27}\)
5,102,417
- Answer
-
none
Exercise \(\PageIndex{28}\)
16,990,792
Exercise \(\PageIndex{29}\)
620,157,659
- Answer
-
none
Exercise \(\PageIndex{30}\)
457,687,705
Exercises for Review
Exercise \(\PageIndex{31}\)
In the number 412, how many tens are there?
- Answer
-
1
Exercise \(\PageIndex{32}\)
Subtract 613 from 810.
Exercise \(\PageIndex{33}\)
Add 35, 16, and 7 in two different ways.
- Answer
-
(35 + 16) + 7 = 51 + 7 = 58
(35 + (16 + 7) = 35 + 23 = 58
Exercise \(\PageIndex{34}\)
Find the quotient \(35 \div 0\), if it exists.
Exercise \(\PageIndex{35}\)
Find the quotient. \(3654 \div 42\).
- Answer
-
87


6.2: Formula Mass
-
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Learning Objectives
By the end of this section, you will be able to:
- Calculate formula masses for covalent and ionic compounds
- Define the amount unit mole and the related quantity Avogadro’s number Explain the relation between mass, moles, and numbers of atoms or molecules, and perform calculations deriving these quantities from one another
Many argue that modern chemical science began when scientists started exploring the quantitative as well as the qualitative aspects of chemistry. For example, Dalton’s atomic theory was an attempt to explain the results of measurements that allowed him to calculate the relative masses of elements combined in various compounds. Understanding the relationship between the masses of atoms and the chemical formulas of compounds allows us to quantitatively describe the composition of substances.
Formula Mass
An earlier chapter of this text described the development of the atomic mass unit, the concept of average atomic masses, and the use of chemical formulas to represent the elemental makeup of substances. These ideas can be extended to calculate the formula mass of a substance by summing the average atomic masses of all the atoms represented in the substance’s formula.
Formula Mass for Covalent Substances
For covalent substances, the formula represents the numbers and types of atoms composing a single molecule of the substance; therefore, the formula mass may be correctly referred to as a molecular mass. Consider chloroform (\(\ce{CHCl3}\)), a covalent compound once used as a surgical anesthetic and now primarily used in the production of tetrafluoroethylene, the building block for the "anti-stick" polymer, Teflon. The molecular formula of chloroform indicates that a single molecule contains one carbon atom, one hydrogen atom, and three chlorine atoms. The average molecular mass of a chloroform molecule is therefore equal to the sum of the average atomic masses of these atoms. Figure \(\PageIndex{1}\) outlines the calculations used to derive the molecular mass of chloroform, which is 119.37 amu.
Likewise, the molecular mass of an aspirin molecule, \(\ce{C9H8O4}\), is the sum of the atomic masses of nine carbon atoms, eight hydrogen atoms, and four oxygen atoms, which amounts to 180.15 amu (Figure \(\PageIndex{2}\)).
 What is the molecular mass (amu) for this compound?
Solution
Molecules of this compound are composed of 13 carbon atoms, 18 hydrogen atoms, and 2 oxygen atoms. Following the approach described above, the average molecular mass for this compound is therefore:
Exercise \(\PageIndex{1}\)
Acetaminophen, C 8 H 9 NO 2 , is a covalent compound and the active ingredient in several popular nonprescription pain medications, such as Tylenol. What is the molecular mass (amu) for this compound?
- Answer
-
151.16 amu
Formula Mass for Ionic Compounds
Ionic compounds are composed of discrete cations and anions combined in ratios to yield electrically neutral bulk matter. The formula mass for an ionic compound is calculated in the same way as the formula mass for covalent compounds: by summing the average atomic masses of all the atoms in the compound’s formula. Keep in mind, however, that the formula for an ionic compound does not represent the composition of a discrete molecule, so it may not correctly be referred to as the “molecular mass.”
As an example, consider sodium chloride, NaCl, the chemical name for common table salt. Sodium chloride is an ionic compound composed of sodium cations, Na + , and chloride anions, Cl − , combined in a 1:1 ratio. The formula mass for this compound is computed as 58.44 amu (see Figure \(\PageIndex{3}\)).
Note that the average masses of neutral sodium and chlorine atoms were used in this computation, rather than the masses for sodium cations and chlorine anions. This approach is perfectly acceptable when computing the formula mass of an ionic compound. Even though a sodium cation has a slightly smaller mass than a sodium atom (since it is missing an electron), this difference will be offset by the fact that a chloride anion is slightly more massive than a chloride atom (due to the extra electron). Moreover, the mass of an electron is negligibly small with respect to the mass of a typical atom. Even when calculating the mass of an isolated ion, the missing or additional electrons can generally be ignored, since their contribution to the overall mass is negligible, reflected only in the nonsignificant digits that will be lost when the computed mass is properly rounded. The few exceptions to this guideline are very light ions derived from elements with precisely known atomic masses.
Example \(\PageIndex{2}\): Computing Formula Mass for an Ionic Compound
Aluminum sulfate, Al 2 (SO 4 ) 3 , is an ionic compound that is used in the manufacture of paper and in various water purification processes. What is the formula mass (amu) of this compound?
Solution
The formula for this compound indicates it contains Al 3 + and SO 4 2 − ions combined in a 2:3 ratio. For purposes of computing a formula mass, it is helpful to rewrite the formula in the simpler format, Al 2 S 3 O 12 . Following the approach outlined above, the formula mass for this compound is calculated as follows:
Exercise \(\PageIndex{2}\)
Calcium phosphate, \(\ce{Ca3(PO4)2}\), is an ionic compound and a common anti-caking agent added to food products. What is the formula mass (amu) of calcium phosphate?
- Answer
-
310.18 amu
The Mole
The identity of a substance is defined not only by the types of atoms or ions it contains, but by the quantity of each type of atom or ion. For example, water, H 2 O, and hydrogen peroxide, H 2 O 2 , are alike in that their respective molecules are composed of hydrogen and oxygen atoms. However, because a hydrogen peroxide molecule contains two oxygen atoms, as opposed to the water molecule, which has only one, the two substances exhibit very different properties. Today, sophisticated instruments allow the direct measurement of these defining microscopic traits; however, the same traits were originally derived from the measurement of macroscopic properties (the masses and volumes of bulk quantities of matter) using relatively simple tools (balances and volumetric glassware). This experimental approach required the introduction of a new unit for amount of substances, the mole , which remains indispensable in modern chemical science.
The mole is an amount unit similar to familiar units like pair, dozen, gross, etc. It provides a specific measure of the number of atoms or molecules in a sample of matter. One Latin connotation for the word “mole” is “large mass” or “bulk,” which is consistent with its use as the name for this unit. The mole provides a link between an easily measured macroscopic property, bulk mass, and an extremely important fundamental property, number of atoms, molecules, and so forth. A mole of substance is that amount in which there are \(6.02214076 \times 10^{23}\).
The molar mass of any substance is numerically equivalent to its atomic or formula weight in amu. Per the amu definition, a single 12 C atom weighs 12 amu (its atomic mass is 12 amu). A mole of 12 C weighs 12 g (its molar mass is 12 g/mol). This relationship holds for all elements, since their atomic masses are measured relative to that of the amu-reference substance, 12 C. Extending this principle, the molar mass of a compound in grams is likewise numerically equivalent to its formula mass in amu (Figure \(\PageIndex{5}\)).
| Element | Average Atomic Mass (amu) | Molar Mass (g/mol) | Atoms/Mole |
|---|---|---|---|
| C | 12.01 | 12.01 | 6.022 10 23 |
| H | 1.008 | 1.008 | 6.022 10 23 |
| O | 16.00 | 16.00 | 6.022 10 23 |
| Na | 22.99 | 22.99 | 6.022 10 23 |
| Cl | 35.45 | 35.45 | 6.022 10 23 |
While atomic mass and molar mass are numerically equivalent, keep in mind that they are vastly different in terms of scale, as represented by the vast difference in the magnitudes of their respective units (amu versus g). To appreciate the enormity of the mole, consider a small drop of water weighing about 0.03 g (see Figure \(\PageIndex{6}\)). Although this represents just a tiny fraction of 1 mole of water (~18 g), it contains more water molecules than can be clearly imagined. If the molecules were distributed equally among the roughly seven billion people on earth, each person would receive more than 100 billion molecules.
Link to Learning
The mole is used in chemistry to represent 6.022 10 23 of something, but it can be difficult to conceptualize such a large number. Watch this video and then complete the “Think” questions that follow. Explore more about the mole by reviewing the information under “Dig Deeper.”
The relationships between formula mass, the mole, and Avogadro’s number can be applied to compute various quantities that describe the composition of substances and compounds, as demonstrated in the next several example problems.
Example \(\PageIndex{3}\): Deriving Moles from Grams for an Element
According to nutritional guidelines from the US Department of Agriculture, the estimated average requirement for dietary potassium is 4.7 g. What is the estimated average requirement of potassium in moles?
Solution
The mass of K is provided, and the corresponding amount of K in moles is requested. Referring to the periodic table, the atomic mass of K is 39.10 amu, and so its molar mass is 39.10 g/mol. The given mass of K (4.7 g) is a bit more than one-tenth the molar mass (39.10 g), so a reasonable “ballpark” estimate of the number of moles would be slightly greater than 0.1 mol.
The molar amount of a substance may be calculated by dividing its mass (g) by its molar mass (g/mol):
The factor-label method supports this mathematical approach since the unit “g” cancels and the answer has units of “mol:”
\[4.7\, \cancel{\text{g K}} \left(\dfrac{\text{mol K}}{39.10\, \cancel{\text{g K}}}\right)=0.12\,\text{mol K} \nonumber \]
The calculated magnitude (0.12 mol K) is consistent with our ballpark expectation, since it is a bit greater than 0.1 mol,
Exercise \(\PageIndex{3}\)
Beryllium is a light metal used to fabricate transparent X-ray windows for medical imaging instruments. How many moles of Be are in a thin-foil window weighing 3.24 g?
- Answer
-
0.360 mol
Example \(\PageIndex{4}\): Deriving Grams from Moles for an Element
A liter of air contains 9.2 10 −4 mol argon. What is the mass of Ar in a liter of air?
Solution
The molar amount of Ar is provided and must be used to derive the corresponding mass in grams. Since the amount of Ar is less than 1 mole, the mass will be less than the mass of 1 mole of Ar, approximately 40 g. The molar amount in question is approximately one-one thousandth (~10 −3 ) of a mole, and so the corresponding mass should be roughly one-one thousandth of the molar mass (~0.04 g):
In this case, logic dictates (and the factor-label method supports) multiplying the provided amount (mol) by the molar mass (g/mol):
\[9.2 \times 10^{-4} \cancel{\text{mol Ar}} \left(\dfrac{39.95\,\text{g Ar}}{\cancel{\text{mol Ar}} }\right)=0.037\,\text{g Ar} \nonumber \]
The result is in agreement with our expectations, around 0.04 g Ar.
Exercise \(\PageIndex{1}\)
What is the mass of 2.561 mol of gold?
- Answer
-
504.4 g
Example \(\PageIndex{5}\): Deriving Number of Atoms from Mass for an Element
Copper is commonly used to fabricate electrical wire (Figure \(\PageIndex{7}\)). How many copper atoms are in 5.00 g of copper wire?
Solution
The number of Cu atoms in the wire may be conveniently derived from its mass by a two-step computation: first calculating the molar amount of Cu, and then using Avogadro’s number ( N A ) to convert this molar amount to number of Cu atoms:
Considering that the provided sample mass (5.00 g) is a little less than one-tenth the mass of 1 mole of Cu (~64 g), a reasonable estimate for the number of atoms in the sample would be on the order of one-tenth N A , or approximately 10 22 Cu atoms. Carrying out the two-step computation yields:
\[5.00 \,\cancel{\text{g Cu}} \left(\frac{\cancel{\text{mol Cu}}}{63.55\,\cancel{\text{g Cu}} }\right)\left(\dfrac{6.022 \times 10^{23} \text{Cu atoms }}{\cancel{\text{ mol Cu}}}\right)=4.74 \times 10^{22} \,\text{Cu atoms} \nonumber \]
The factor-label method yields the desired cancellation of units, and the computed result is on the order of 10 22 as expected.
Exercise \(\PageIndex{5}\)
A prospector panning for gold in a river collects 15.00 g of pure gold. How many Au atoms are in this quantity of gold?
- Answer
-
\(4.586 \times 10^{22}\,\text{Au atoms}\)
Example \(\PageIndex{6}\): Deriving Moles from Grams for a Compound
Our bodies synthesize protein from amino acids. One of these amino acids is glycine, which has the molecular formula C 2 H 5 O 2 N. How many moles of glycine molecules are contained in 28.35 g of glycine?
Solution
Derive the number of moles of a compound from its mass following the same procedure used for an element in Example \(\PageIndex{3}\):
The molar mass of glycine is required for this calculation, and it is computed in the same fashion as its molecular mass. One mole of glycine, C 2 H 5 O 2 N, contains 2 moles of carbon, 5 moles of hydrogen, 2 moles of oxygen, and 1 mole of nitrogen:
The provided mass of glycine (~28 g) is a bit more than one-third the molar mass (~75 g/mol), so the computed result is expected to be a bit greater than one-third of a mole (~0.33 mol). Dividing the compound’s mass by its molar mass yields:
\[28.35 \cancel{\text { g glyeine }} \left(\frac{\text { mol glycine }}{75.07 \cancel{\text { g glyeine} }}\right)=0.378 \, \text{mol glycine } \nonumber \]
This result is consistent with the rough estimate,
Exercise \(\PageIndex{6}\)
How many moles of sucrose, C 12 H 22 O 11 , are in a 25-g sample of sucrose?
- Answer
-
0.073 mol
Example \(\PageIndex{7}\): Deriving Grams from Moles for a Compound
Vitamin C is a covalent compound with the molecular formula C 6 H 8 O 6 . The recommended daily dietary allowance of vitamin C for children aged 4–8 years is 1.42 10 −4 mol. What is the mass of this allowance in grams?
Solution
As for elements, the mass of a compound can be derived from its molar amount as shown:
The molar mass for this compound is computed to be 176.124 g/mol. The given number of moles is a very small fraction of a mole (~10 −4 or one-ten thousandth); therefore, the corresponding mass is expected to be about one-ten thousandth of the molar mass (~0.02 g). Performing the calculation yields:
\[1.42 \times 10^{-4} \cancel{\text { mol vitamin C}} \left(\frac{176.124 \, \text{g vitamin C}}{\cancel{\text { mol vitamin C}}}\right)=0.0250\, \text{g vitamin C} \nonumber \]
This is consistent with the anticipated result.
Exercise \(\PageIndex{7}\)
What is the mass of 0.443 mol of hydrazine, N 2 H 4 ?
- Answer
-
14.2 g
Example \(\PageIndex{8}\): Deriving the Number of Atoms and Molecules from the Mass of a Compound
A packet of an artificial sweetener contains 40.0 mg of saccharin (C 7 H 5 NO 3 S), which has the structural formula:
Given that saccharin has a molar mass of 183.18 g/mol, how many saccharin molecules are in a 40.0-mg (0.0400-g) sample of saccharin? How many carbon atoms are in the same sample?
Solution
The number of molecules in a given mass of compound is computed by first deriving the number of moles, as demonstrated in Example \(\PageIndex{6}\), and then multiplying by Avogadro’s number:
Using the provided mass and molar mass for saccharin yields:
\[\begin{align*}
& 0.0400\, \cancel{\text{g}\,\ce{C7H5NO3S}} \left(\frac{\cancel{\text{mol} \, \ce{C7H5NO3S}} }{183.18\, \cancel{\text{g}\, \ce{CH5NO3S}} }\right)\left(\frac{6.022 \times 10^{23} \,\ce{C7H5NO3S} \text { molecules }}{1\, \cancel{\text{mol} \, \ce{C7H5NO3S}}}\right) \\
& =1.31 \times 10^{20} \, \ce{C7H5NO3S} \text { molecules }
\end{align*} \nonumber \]
The compound’s formula shows that each molecule contains seven carbon atoms, and so the number of C atoms in the provided sample is:
\[1.31 \times 10^{20} \,\ce{C7H5NO3S} \text { molecules }\left(\frac{7\,\ce{C} \,\text { atoms }}{1 \,\ce{C7H5NO3S} \text { molecule }}\right)=9.17 \times 10^{20} \,\ce{C} \text { atoms } \nonumber \]
Exercise \(\PageIndex{8}\)
How many C 4 H 10 molecules are contained in 9.213 g of this compound? How many hydrogen atoms?
- Answer
-
9.545 × 10 22 molecules C 4 H 10
9.545 × 10 23 atoms H
How Sciences Interconnect: Counting Neurotransmitter Molecules in the Brain
The brain is the control center of the central nervous system (Figure \(\PageIndex{8}\)). It sends and receives signals to and from muscles and other internal organs to monitor and control their functions; it processes stimuli detected by sensory organs to guide interactions with the external world; and it houses the complex physiological processes that give rise to our intellect and emotions. The broad field of neuroscience spans all aspects of the structure and function of the central nervous system, including research on the anatomy and physiology of the brain. Great progress has been made in brain research over the past few decades, and the BRAIN Initiative, a federal initiative announced in 2013, aims to accelerate and capitalize on these advances through the concerted efforts of various industrial, academic, and government agencies (more details available at www.whitehouse.gov/share/brain-initiative).
Specialized cells called neurons transmit information between different parts of the central nervous system by way of electrical and chemical signals. Chemical signaling occurs at the interface between different neurons when one of the cells releases molecules (called neurotransmitters) that diffuse across the small gap between the cells (called the synapse) and bind to the surface of the other cell. These neurotransmitter molecules are stored in small intracellular structures called vesicles that fuse to the cell membrane and then break open to release their contents when the neuron is appropriately stimulated. This process is called exocytosis (see Figure \(\PageIndex{9}\)). One neurotransmitter that has been very extensively studied is dopamine, C 8 H 11 NO 2 . Dopamine is involved in various neurological processes that impact a wide variety of human behaviors. Dysfunctions in the dopamine systems of the brain underlie serious neurological diseases such as Parkinson’s and schizophrenia.
One important aspect of the complex processes related to dopamine signaling is the number of neurotransmitter molecules released during exocytosis. Since this number is a central factor in determining neurological response (and subsequent human thought and action), it is important to know how this number changes with certain controlled stimulations, such as the administration of drugs. It is also important to understand the mechanism responsible for any changes in the number of neurotransmitter molecules released—for example, some dysfunction in exocytosis, a change in the number of vesicles in the neuron, or a change in the number of neurotransmitter molecules in each vesicle.
Significant progress has been made recently in directly measuring the number of dopamine molecules stored in individual vesicles and the amount actually released when the vesicle undergoes exocytosis. Using miniaturized probes that can selectively detect dopamine molecules in very small amounts, scientists have determined that the vesicles of a certain type of mouse brain neuron contain an average of 30,000 dopamine molecules per vesicle (about \(5 \times 10^{−20}\,\text{mol}\) or \(50 \,\text{zmol}\)). Analysis of these neurons from mice subjected to various drug therapies shows significant changes in the average number of dopamine molecules contained in individual vesicles, increasing or decreasing by up to three-fold, depending on the specific drug used. These studies also indicate that not all of the dopamine in a given vesicle is released during exocytosis, suggesting that it may be possible to regulate the fraction released using pharmaceutical therapies.
Footnotes
- 1 Omiatek , Donna M., Amanda J. Bressler, Ann-Sofie Cans, Anne M. Andrews, Michael L. Heien, and Andrew G. Ewing. “The Real Catecholamine Content of Secretory Vesicles in the CNS Revealed by Electrochemical Cytometry.” Scientific Report 3 (2013): 1447, accessed January 14, 2015, doi:10.1038/srep01447.


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amino acid pool
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molecules of essential and nonessential amino acids regulated by the liver and available for use by the body
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bioavailability
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the ability of an organic substance to enter the circulation and produce an active effect
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carbohydrates
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large food category that includes starches, cellulose, and sugars
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complex carbohydrates
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long chains of monosaccharides such as those found in starch
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disaccharides
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compounds containing two monosaccharide molecules
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glucose
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simple monosaccharide that is an important energy source and is found in carbohydrates
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glycemic index
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system that ranks foods on a scale from 1 to 100 based on their effect on blood glucose levels
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glycemic load
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method of indicating the amount of carbohydrate contained in a specified serving of a particular food and its impact on blood glucose
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glycogen
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stored form of glucose
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high-density lipoprotein
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molecule comprising lipids and proteins; it removes cholesterol from the blood
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low-density lipoprotein
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molecule comprising lipids and proteins; it transports cholesterol throughout the bloodstream
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monosaccharide
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sugar molecule that cannot be further metabolized
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polypeptides
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linear organic molecules consisting of many amino acid residues bonded together in a chain, forming part or all of a protein
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proteolysis
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enzymatic breakdown of proteins or peptides into amino acids
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triglycerides
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compounds formed from glycerol and three fatty acid groups; the main constituents of natural fats and oils
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ultraprocessed foods
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foods altered by commercial techniques, usually by adding five or more artificial substances
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whole foods
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foods that have been processed or refined as little as possible and are free from additives and other artificial substances


11.2.3: Evaluating Your Case for Fair Use
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Copyright law lacks specificity, so it can be difficult to determine whether or not a particular use may qualify as fair use. Fortunately, there are a number of useful tools available online to help you consider the four fair use factors as they apply to your intended use.
A Fair Use Checklist can be very helpful for conducting a fair use analysis. The checklist indicates various criteria for each factor which have been found in a court of law to favor or oppose a finding of fair use. It is highly recommended that you use a fair use checklist to evaluate the strength of your argument for fair use.
Video Clip: Follow the Four Factors of Fair Use
Watch this video to see a fair use analysis using a fair use checklist.
A YouTube element has been excluded from this version of the text. You can view it online
here
.
In a fair use analysis, you consider each of the four factors in light of your proposed use and determine whether your use is favoring or opposing fair use for that factor.
You then weigh all four factors together. You cannot rely on a numerical tallying of criteria in favor and opposing fair use in order to make a determination. You must consider all four factors holistically and determine if, taken as a whole, they favor or oppose fair use, and to what extent (e.g. strongly favoring fair use, slightly favoring, etc.).
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If, overall, your use favors fair use, then you may proceed.
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If your use instead opposes fair use, you should reassess your use and determine if you can make any changes that could strengthen your case for fair use.
There are other tools in addition to the checklist that can help you conduct a fair use analysis. The American Library Association has developed a tool called the
Fair Use Evaluator
.
Activity: Fair Use Criteria
Visit the Fair Use Checklist and review the criteria for each of the four factors.
Tips for Best Practice
While it is important to perform a fair use evaluation for each and every use of copyrighted material, there are some general rules that can often help you to strengthen a fair use claim.
Below are a few tips to consider when relying on the fair use exception in order to use copyrighted works in your endeavors.
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Use only lawfully acquired copyrighted works
– To be able to claim fair use you must have used a legal copy of the original work.
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Acknowledge all of your sources with a bibliographic citation
– Giving proper credit to the original creator demonstrates good faith and may help strengthen your fair use case.
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Use only the amount of the original work that you need to accomplish your goal
– Since the amount of the original work that is used is one of the fair use factors, it is always important to only use what you need and not add extra material.
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Restrict the audience and/or make only the number of copies that you need
– The less you copy and share the parts of the original work, the less effect you have on the market for it.
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Use Creative Commons licensed or public domain works
– If you use works that expressly allow you to use them or have no copyright protection, you do not need to rely on fair use and can be more confident that your use is legal.
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Use works that you created
– If you created it, you own the copyright, with the exception of works made for hire. (When you create things for your job, typically your employer owns the copyright.)
If you are in doubt about your fair use claim, either reassess and make changes to your proposed use in order to make a stronger claim or ask for permission to use the copyrighted material
– It is much easier to make changes or ask for permission before you use copyrighted material than to get hit with an infringement claim and have to make changes or face a law suit after your use.
Further Reading on Fair Use
A number of groups have developed Codes of Best Practices in Fair Use for different types of activities. These codes propose examples of fair use within specific communities of practice. Below are links to some of these Codes of Best Practices.


4.1.2: Gender and Socialization
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Gender Socialization
Gender socialization is the process by which males and females are informed about the norms and behaviors associated with their sex.
Learning Objectives
Explain the influence of socialization on gender roles and their impact
Key Points
- Gender socialization is the process by which individuals are taught how to socially behave in accordance with their assigned gender, which is assigned at birth based on their biological sex.
- Today it is largely believed that most gender differences are attributed to differences in socialization, rather than genetic and biological factors.
- Gender stereotypes can be a result of gender socialization: girls and boys are expected to act in certain ways that are socialized from birth. Children and adults who do not conform to gender stereotypes are often ostracized by peers for being different.
- While individuals are typically socialized into viewing gender as a masculine-feminine binary, there are individuals who challenge and complicate this notion. These individuals believe that gender is fluid and not a rigid binary.
Key Terms
- Gender socialization : The process of educating and instructing males and females as to the norms, behaviors, values, and beliefs of group membership as men or women.
- gender : The socio-cultural phenomenon of the division of people into various categories such as male and female, with each having associated roles, expectations, stereotypes, etc.
- sex : Either of two main divisions (female or male) into which many organisms can be placed, according to reproductive function or organs.
Sociologists and other social scientists generally attribute many of the behavioral differences between genders to socialization. Socialization is the process of transferring norms, values, beliefs, and behaviors to group members. The most intense period of socialization is during childhood, when adults who are members of a particular cultural group instruct young children on how to behave in order to comply with social norms.  Gender socialization is thus the process of educating and instructing males and females as to the norms, behaviors, values, and beliefs of group membership.
Preparations for gender socialization begin even before the birth of the child. One of the first questions people ask of expectant parents is the sex of the child. This is the beginning of a social categorization process that continues throughout life. Preparations for the birth often take the infant’s sex into consideration (e.g., painting the room blue if the child is a boy, pink for a girl). Today it is largely believed that most gender differences are attributed to differences in socialization, rather than genetic and biological factors.
Gender stereotypes can be a result of gender socialization. Girls and boys are expected to act in certain ways, and these ways are socialized from birth by many parents (and society). For example, girls are expected to be clean and quiet, while boys are messy and loud. As children get older, gender stereotypes become more apparent in styles of dress and choice of leisure activities. Boys and girls who do not conform to gender stereotypes are usually ostracized by same-age peers for being different. This can lead to negative effects, such as lower self-esteem.
In Western contexts, gender socialization operates as a binary, or a concept that is exclusively comprised of two parts. In other words, individuals are socialized into conceiving of their gender as either masculine (male) or feminine (female). Identities are therefore normatively constructed along this single parameter. However, some individuals do not feel that they fall into the gender binary and they choose to question or challenge the male-masculine / female-feminine binary. For example, individuals that identify as transgender feel that their gender identity does not match their biological sex. Individuals that identify as genderqueer challenge classifications of masculine and feminine, and may identify as somewhere other than male and female, in between male and female, a combination of male and female, or a third (or forth, or fifth, etc.) gender altogether. These identities demonstrate the fluidity of gender, which is so frequently thought to be biological and immutable. Gender fluidity also shows how gender norms are learned and either accepted or rejected by the socialized individual.
The Social Construction of Gender
Social constructivists propose that there is no inherent truth to gender; it is constructed by social expectations and gender performance.
Learning Objectives
Explain Judith Butler’s concept of gender performativity
Key Points
- Social constructionism is the notion that people’s understanding of reality is partially, if not entirely, socially situated.
- Gender is a social identity that needs to be contextualized.
- Individuals internalize social expectations for gender norms and behave accordingly.
Key Terms
- Gender performativity : Gender Performativity is a term created by post-structuralist feminist philosopher Judith Butler in her 1990 book Gender Trouble, which has subsequently been used in a variety of academic fields that describes how individuals participate in social constructions of gender.
- social constructionism : The idea that social institutions and knowledge are created by actors within the system, rather than having any inherent truth on their own.
- essentialism : The view that objects have properties that are essential to them.
Social Constructionism
The social construction of gender comes out of the general school of thought entitled social constructionism. Social constructionism proposes that everything people “know” or see as “reality” is partially, if not entirely, socially situated. To say that something is socially constructed does not mitigate the power of the concept. Take, for example, money. Money is a socially constructed reality. Paper bills are worth nothing independent of the value individuals ascribe to them. The dollar is only worth as much as value as Americans are willing to ascribe to it. Note that the dollar only works in its own currency market; it holds no value in areas that don’t use the dollar. Nevertheless, the dollar is extremely powerful within its own domain.
These basic theories of social constructionism can be applied to any issue of study pertaining to human life, including gender. Is gender an essential category or a social construct ? If it is a social construct, how does it function? Who benefits from the way that gender is constructed? A social constructionist view of gender looks beyond categories and examines the intersections of multiple identities and the blurring of the boundaries between essentialist categories. This is especially true with regards to categories of male and female, which are viewed typically as binary and opposite. Social constructionism seeks to blur the binary and muddle these two categories, which are so frequently presumed to be essential.
Judith Butler and Gender Performativity
Judith Butler is one of the most prominent social theorists currently working on issues pertaining to the social construction of gender. Butler is a trained philosopher and has oriented her work towards feminism and queer theory. Butler’s most known work is Gender Trouble: Feminism and the Subversion of Identity , published in 1991, which argues for gender performativity. This means that gender is not an essential category. The repetitious performances of “male” and “female” in accordance with social norms reifies the categories, creating the appearance of a naturalized and essential binary. Gender is never a stable descriptor of an individual, but an individual is always “doing” gender, performing or deviating from the socially accepted performance of gender stereotypes. Doing gender is not just about acting in a particular way. It is about embodying and believing certain gender norms and engaging in practices that map on to those norms. These performances normalize the essentialism of gender categories. In other words, by doing gender, we reinforce the notion that there are only two mutually exclusive categories of gender. The internalized belief that men and women are essentially different is what makes men and women behave in ways that appear essentially different. Gender is maintained as a category through socially constructed displays of gender.
Doing gender is fundamentally a social relationship. One does gender in order to be perceived by others in a particular way, either as male, female, or as troubling those categories. Certainly, gender is internalized and acquires significance for the individual; some individuals want to feel feminine or masculine. Social constructionists might argue that because categories are only formed within a social context, even the affect of gender is in some ways a social relation. Moreover, we hold ourselves and each other for our presentation of gender, or how we “measure up.” We are aware that others evaluate and characterize our behavior on the parameter of gender. Social constructionists would say that gender is interactional rather than individual—it is developed through social interactions. Gender is also said to be omnirelevant, meaning that people are always judging our behavior to be either male or female.
Gender Identity in Everyday Life
Gender identity is one’s sense of one’s own gender. It is the result of socialization, but it also has a biological basis.
Learning Objectives
Discuss the difference between biological and social construction of gender identity
Key Points
- Gender identity typically falls on a gender binary —individuals are expected to exclusively identify either as male or female. However, some individuals believe that this binary model is illegitimate and identify as a third, or mixed, gender.

- Gender identity discourse derives from medical and psychological conceptions of gender. There is vigorous debate over biological versus environmental causes of the development of one’s gender identity.
- As gender identities come to be more disputed, new legal frontiers are opening on the basis that a male/female gender binary, as written into the law, discriminates against individuals who either identify as the opposite of their biological sex or who do not identify as either male or female.
- The extreme cultural variation in notions of gender indicate the socially constructed nature of gender identity.
Key Terms
- cisgender : Identifying with or experiencing a gender the same as one’s biological sex or that is affirmed by society, e.g. being both male-gendered & male-sexed.
- transgender : Not identifying with culturally conventional gender roles and categories of male or female; having changed gender identity from male to female or female to male, or identifying with elements of both, or having some other gender identity.
- gender binary : A view of gender whereby people are categorized exclusively as either male or female, often basing gender on biological sex.
Gender identity is one’s sense of being male, female, or a third gender. Gender identity typically falls on a gender binary—individuals are expected to exclusively identify either as male or female. However, some individuals believe that this binary model is illegitimate and identify as a third, or mixed, gender. Gender identity is socially constructed, yet it still pertains to one’s sense of self. Gender identity is not only about how one perceives one’s own gender, but also about how one presents one’s gender to the public.
   Transsexuals, however, take drastic measures to assume their believed identity. This includes hormone therapy and sexual reassignment operations. Recently, there has been a growing gender/queer movement consisting of individuals who do not feel that their sex organs are mismatched to their gender identity, but who still wish to trouble the notion of a gender binary, considering it overly simplistic and misrepresentative.
Causes of Confusion in Gender Identity
What causes individuals to sense a sort of confusion between their biological gender and their gender identity? This question is hotly contested, with no clear answer. Some scientists argue that the sense of confusion is a biological result of the pre- and post-natal swinging of hormone levels and genetic regulation. Sociologists tend to emphasize the environmental impetuses for gender identity. Certainly, socialization, or the process of transferring norms, values, beliefs, and behaviors to group members, plays a significant part in how individuals learn and internalize gender roles and subsequently impact their gender identity.
Though the medical emphasis in some conversations about gender identity is frequently scrutinized by sociologists, there is clearly some biological basis to gender, even if it has more to do with appearances and social presentation than identity formation. Women have two X chromosomes, where men have one X and one Y chromosome. However, despite the deep relationship to biology, gender identity cannot only be biologically determined. However, gender identity has a larger social component that needs to be considered. For example, although a person may be biologically male, “he” may feel more comfortable with a female identity, which is a social construction based on how he feels, not his physical makeup.
Gender Identities and Law
As gender identities come to be more disputed, new legal frontiers are opening on the basis that a male/female gender binary, as written into the law, discriminates against individuals who either identify as the opposite of their biological sex or who identify as neither male nor female. On college campuses, gender-restrictive dorm housing is facing opposition by individuals who identify as neither a man nor a woman. Many public spaces and workplaces are instituting gender-neutral bathroom facilities. Gender identity has become a piece of international law as a branch of human rights doctrines. The Yogyakarta Principles, drafted by international legal scholars in 2006, provide a definition of gender identity in its preamble. In the Principles “gender identity” refers to each person’s deeply felt internal and individual experience of gender, which may or may not correspond with the biological sex assigned at birth, including the person’s sense of the body and other expressions of gender.
Gender Identities across Cultures
Gender identities, and the malleability of the gender binary, vary across cultures. In some Polynesian societies, fa’afafine are considered to be a third gender alongside male and female. Fa’afafine are accepted as a natural gender and are neither looked down upon nor discriminated against. They are biologically male, but dress and behave in a manner that Polynesians typically consider female. Fa’afafine are often physiologically unable to reproduce. Fa’afafine also reinforce their femininity by claiming to be only attracted to and receiving sexual attention from heterosexual men.
In the Indian subcontinent, a hijra is usually considered to be neither male nor female. The hijra form a third gender, although they do not enjoy the same acceptance and respect as individuals who identify along the gender binary.
The xanith form an accepted third gender in Oman, a society that also holds a gender binary as a social norm.  Xanith can mingle with women where men cannot. However, similar to other men in Oman, xanith can marry women and prove their masculinity by consummating the marriage. This extreme cultural variation in notions of gender indicate the socially constructed nature of gender identity.
Gender Roles in the U.S.
Gender roles refer to the set of social and behavioral norms that are considered to be appropriate for people of a specific sex.
Learning Objectives
Describe how gender roles in the U.S. have changed since the 1950’s
Key Points
- Gender roles are never universal, even within a single country, and they are always historically and culturally contingent.
- Gender role theory emphasizes environmental conditions and the influence of socialization, or the process of transferring norms, values, beliefs, and behaviors to group members, in learning how to behave as a male or female.
- Current trends toward a total integration model of gender roles is reflected in women’s education, professional achievement, and family income contributions.
Key Terms
- nuclear family : a family unit consisting of at most a father, mother and dependent children.
- socialization : The process of learning one’s culture and how to live within it.
- Division of labor : A division of labour is the dividing and specializing of cooperative labour into specifically circumscribed tasks and roles.
Gender roles refer to the set of social and behavioral norms that are considered to be socially appropriate for individuals of a specific sex. There has been significant variation in gender roles over cultural and historical spans, and all gender roles are culturally and historically contingent. Much scholarly work on gender roles addresses the debate over the environmental or biological causes for the development of gender roles. The following section seeks to orient the reader to the sociological theorization of the gender role and discuss its application in an American context.
Gender and Social Role Theory
Gender role theory posits that boys and girls learn to perform one’s biologically assigned gender through particular behaviors and attitudes. Gender role theory emphasizes the environmental causes of gender roles and the impact of socialization, or the process of transferring norms, values, beliefs, and behaviors to group members, in learning how to behave as a male or a female. Social role theory proposes that the social structure is the underlying force in distinguishing genders and that sex-differentiated behavior is driven by the division of labor between two sexes within a society. The division of labor creates gender roles, which in turn, lead to gendered social behavior.
Gender Roles in the United States
With the popularization of social constructionist theories of gender roles, it is paramount that one recognize that all assertions about gender roles are culturally and historically contingent. This means that what might be true of gender roles in the United States for one cultural group likely is not true for another cultural group. Similarly, gender roles in the United States have changed drastically over time. There is no such thing as a universal, generalizable statement about gender roles.
One main thread in discussions about gender roles in the United States has been the historical evolution from a single-income family, or a family unit in which one spouse (typically the father) is responsible for the family income, to a dual-income family, or a family unit in which both spouses generate income. Before the rise of feminism in the 1960s and 1970s and the influx of women into the workforce in the 1980s, women were largely responsible for dealing with home matters, while men worked and earned income outside the home. While some claim that this was a sexist structure, others maintain that the structure simply represented a division of labor, or a social system in which a particular segment of the population performs one type of labor and another segment performs another type.
Nuclear Family Models
In 1955, sociologist Talcott Parsons developed a model of nuclear families in the United States that addressed gender roles. Family structures vary across cultures and history, and the term nuclear family refers to a family unit of two parents and their children. Parsons developed two models of gender roles within the nuclear family. His first model involved total role segregation; men and women would be trained and educated in gender-specific institutions, and high professional qualifications and the workplace would be intended for men. Women would be primarily focused on housekeeping, childcare, and children’s education. Male participation in domestic activity would be only partially desired and socially acceptable. Further, in the case of conflict, the man would have the final say. Parsons contrasted this first model with a second that involved the total integration of roles. In the second model, men and women would be educated in the same institutions and study the same content in classes. Outside the educational milieu, women and men would both perceive career to be important, and equal professional opportunities for men and women would be considered socially necessary. Both parties in a marriage would bear responsibility for housework and child rearing. Finally, neither gender would systematically dominate decision making.
Current Trends
Of course, neither of Parsons’s models accurately described the United States in the 1950s, and neither model accurately describes the United States in the present day. However, total role segregation was closer to the reality of the United States in the 1950s, whereas a total integration of roles is increasingly common in the United States today.
The national trend toward a total integration of gender roles is reflected in women’s education, professional achievement, and family income contributions. Currently, more women than men are enrolled in college, and women are expected to earn more graduate degrees than men over the next several years. In 2005, 22% of American households had two income earners, which suggests the presence of women in the workforce. However, in most contexts, women are still expected to be the primary homemakers, even if they are contributing to household income by working outside the home.
The Cross-Cultural Perspective
Gender roles vary widely across different cultural contexts.
Learning Objectives
Compare and contrast gender roles in different cultures
Key Points
- It is impossible to generalize what life is like for one woman from assumptions about gender roles in different countries.
- To assess what daily life is like for women, one must learn the particulars about the cultural and historical moment she occupies.
- In Sweden, all working parents are entitled to sixteen months paid leave per child. To encourage greater paternal involvement in childrearing, a minimum of two months out of the sixteen is required to be used by the “minority” parent, usually the father.
- 62% of Chileans are opposed to full gender equality and believe that women should limit themselves to the roles of mother and wife. Until recently, women lost their right to administer their own assets once they were married, and were required by law to obey their husbands.
- Women in Japan are usually well-educated and employed, though gender dynamics emerge in regards to social pressure to find a husband. Historically, gender has been an important principle of Japanese social stratification, but gender differences have varied over time and within social class.
Key Terms
- Michelle Bachelet : Chile’s first female president (2006-2010).
- parental leave : A leave of absence from a job for a parent to take care of a baby.
Gender roles vary significantly across cultures. Indeed, all gender roles are culturally and historically contingent, meaning that they cannot be analyzed outside of their cultural and historical contexts. This section attempts to provide a few examples of variation in gender roles and the lives of women in various places around the world. These small glimpses are not universal by any means, but this overview should provide a brief summary of just how much women’s lives vary and how much women’s lives seem similar across national boundaries.
Gender Roles in Sweden
Governments in Europe are typically more active in governing the lives of their citizens than the U.S. government. As such, European governments have used their social powers to encourage equality between men and women. In Sweden, for example, all working parents are entitled to sixteen months paid leave per child, with the cost shared by the government and the employer. To encourage greater paternal involvement in childrearing, a minimum of two months out of the sixteen is required to be used by the “minority” parent, usually the father. Through policies such as parental leave, European states actively work to promote equality between genders in childrearing and professional lives.
Gender Roles In Chile
As is the case for many women in the United States and in Europe, many women in Chile feel pressure to conform to traditional gender roles. A 2010 study by the United Nations Development Programme found that 62% of Chileans are opposed to full gender equality and expressed the belief that women should limit themselves to the roles of mother and wife. These social barriers to gender equality exist in the face of legal equality.
Chilean law has recently undergone some drastic changes to support gender equality. Until recently, women lost their right to administer their own assets once they were married, with their husbands receiving all of their wealth. Now, a woman is allowed to maintain her own property. Previously, women were legally required to live with and be faithful and obedient to her husband, but now it is not law.
Chile grants both men and women the right to vote and had one of the first female presidents in the world. From 2006 until 2010, Michelle Bachelet served as Chile’s first female president. Women are gaining increasingly prominent positions in various aspects of government. The prominence of female politicians is working to undo traditional stereotypes of women belonging only in the domestic sphere.
Gender Roles in Japan
Women in Japan are usually well-educated and employed, though gender dynamics emerge in regards to social pressure to find a husband. Historically, gender has been an important principle of Japanese social stratification but the cultural elaboration of gender differences has, of course, varied over time and within social class. After World War II, the legal position of women was redefined by the occupation authorities. Individual rights were given precedence over obligation to family. Women were guaranteed the right to choose spouses and occupations, to inherit and own property in their own names, and to retain custody of their children. Women were granted the right to vote in 1946. Legally, few barriers to women’s equal participation in social and professional life remain in Japan.
However, gender inequality continues in family life, the workplace, and popular values. A common Japanese proverb that continues to influence gender roles is “good wife, wise mother. ” The proverb reflects the still common social belief, encouraged by men and women alike, that it is in the woman’s, her children’s, and society’s best interests for her to stay home and devote herself to her children. In most households, women are responsible for family budgets and make independent decisions about the education, careers, and life styles of their families.
Better educational prospects are improving women’s professional prospects. Immediately after World War II, the common image of womanhood was that of a secretary who becomes a housewife and mother after marriage. But a new generation of educated woman is emerging who wishes to establish a career in the workforce. Japanese women are joining the labor force in unprecedented numbers such that around 50% of the workforce is comprised of women. One important change is that married women have begun to participate in the work force. In the 1950s, most female employees were young and single; 62% of the female labor force had never been married. By 1987, 68% of the female workforce was married and only 23% had never been married.
Despite changes in the workforce, women are still expected to get married. It is common for unmarried women to experience anxiety and social pressure as a result of her unwed status.
These examples from Sweden, Chile, and Japan hardly scratch the surface of demonstrating some of the extreme variation in gender roles worldwide.
Childhood Socialization
Gender roles are taught from infancy through primary socialization, or the type of socialization that occurs in childhood and adolescence.
Learning Objectives
Describe how society socializes children to accept gender norms
Key Points
- Gender is instilled through socialization immediately from birth. Consider the gender norms with which society imbues infants. The most archetypal example is the notion that male babies like blue things while female babies like pink things.
- The example set by an individual’s family is also important for socialization. For example, children who grow up in a family with the husband a breadwinner and the wife a homemaker will tend to accept this as the social norm.
- Children sometimes resist gender norms by behaving in ways more commonly associated with the opposite gender.
Key Terms
- socialization : The process of learning one’s culture and how to live within it.
- primary socialization : The socialization that takes place early in life, as a child and adolescent.
- secondary socialization : The socialization that takes place throughout one’s life, both as a child and as one encounters new groups that require additional socialization.
Social norms pertaining to gender are developed through socialization, the lifelong process of inheriting, interpreting, and disseminating norms, customs, and ideologies.The process of socialization continues throughout one’s life and is constantly renegotiated, but socialization begins as soon as one is born. Sociologists divide socialization into two different parts. Primary socialization takes place early in life, as a child and adolescent. Secondary socialization refers to the socialization that takes place throughout one’s life, both as a child and as one encounters new groups that require additional socialization.
Gender is instilled through socialization immediately from birth. Consider the gender norms with which society imbues infants: The most archetypal example is the notion that male babies like blue things while female babies like pink things. When a boy gets a football for his birthday and a girl receives a doll, this also socializes children to accept gender norms. The example set by an individual’s family is also important for socialization; children who grow up in a family with the husband a breadwinner and the wife a homemaker will tend to accept this as the social norm, while those who grow up in families with female breadwinners, single parents, or same-sex couples will develop different ideas of gender norms.
Because gender norms are perpetuated immediately upon birth, many sociologists study what happens when children fail to adopt the expected gender norms rather than the norms themselves. This is the standard model of studying deviance in order to understand the norm that undergirds the deviant activity. Children can resist gender norms by insisting on dressing in clothing more typically associated with the other gender, playing with toys more typically associated with the other gender, or having opposite-sex playmates.
Adolescent Socialization
Adolescence is a transitional stage of biological, cognitive and social development that prepares individuals for taking on adult roles.
Learning Objectives
Describe the three general approaches to understanding identity development
Key Points
- Identity development is a normative process of change in both the content and structure of how people think about themselves. Identity development encompasses the following notions: self-concept, sense of identity and self-esteem.
- Self-concept is the awareness of the self in relation to a variety of different characteristics and concepts.
- A sense of identity is much more integrated and less conflicting than the self-concept, as an identity is a coherent sense of self that is consistent across different contexts and circumstances past, present and future.
- Self-esteem is one’s perception of and feelings toward one’s self-concept and identity.
- Familial, peer and sexual/romantic relationships exert a siginficant influence over adolescent development and can encourage either positive or negative outcomes.
Key Terms
- identity : A coherent sense of self stable across circumstances and including past experiences and future goals.
Adolescence is a transitional stage of physical and psychological human development. The period of adolescence is most closely associated with the teenage years, although its physical, psychological and cultural expressions can begin earlier and end later. In studying adolescent development, adolescence can be defined biologically as the physical transition marked by the onset of puberty and the termination of physical growth; cognitively, as changes in the ability to think abstractly and multi-dimensionally; and socially as a period of preparation for adult roles. Major pubertal and biological changes include changes to the sex organs, height, weight and muscle mass, as well as major changes in brain structure and organization. Cognitive advances encompass both increases in knowledge and the ability to think abstractly and to reason more effectively. This is also a time when adolescents start to explore gender identity and sexuality in depth.
Identity Development
Among the most common beliefs about adolescence is that it is the time when teens form their personal identities. Empirical studies confirm a normative process of change in both the content and structure of one’s thoughts about the self. Researchers have used three general approaches to understanding identity development: self-concept, sense of identity and self-esteem.
Self-Concept
Early in adolescence, cognitive developments result in greater self-awareness, greater awareness of others and their thoughts and judgments, the ability to think about abstract, future possibilities, and the ability to consider multiple possibilities at once. While children define themselves with physical traits, adolescents define themselves based on their values, thoughts and opinions. Adolescents can now conceptualize multiple “possible selves” they could become and long-term possibilities and consequences of their choices. Exploring these possibilities may result in abrupt changes in self-presentation as the adolescent chooses or rejects qualities and behaviors, trying to guide the actual self toward the ideal self (who the adolescent wishes to be) and away from the feared self (who the adolescent does not want to be). In terms of gender socialization, boys and girls start to gravitate toward traditional roles. For example, girls may take more liberal art type classes while boys are more physical. Boys and girls tend to socialize together, although dating starts to occur. Girls generally look to their mothers or female role models for guidance, while boys tend to identify more with their fathers or male role models.
Sense of Identity
Unlike the conflicting aspects of self-concept, identity represents a coherent sense of self stable across circumstances and including past experiences and future goals. Development psychologist Erik Erikson describes adolescence as the period during which individuals ponder the questions: who am I and what can I be? As they make the transition from childhood to adulthood, adolescents ponder the roles they will play in the adult world. Initially, they are apt to experience some role confusion—mixed ideas and feelings about the specific ways in which they will fit into society—and may experiment with a variety of behaviors and activities. For example, a girl may want to pursue a career that is predominantly male, and if she is stifled by her sense of female identity, she may end up with a lifetime of regret. The same is true of males wishing to pursue a female-dominated career. Erikson proposed that most adolescents eventually achieve a sense of identity regarding who they are and where their lives are headed.
Self-Esteem
The final major aspect of identity formation is self-esteem, which is one’s thoughts and feelings about one’s self-concept and identity. Contrary to popular belief, there is no empirical evidence for a significant drop in self-esteem over the course of adolescence. “Barometric self-esteem” fluctuates rapidly and can cause severe distress and anxiety, but baseline self-esteem remains highly stable across adolescence.The validity of global self-esteem scales has been questioned, and many suggest that more specific scales might reveal more about the adolescent experience. For girls, they are most likely to enjoy high self-esteem when engaged in supportive relationships with friends, as the most important function of friendship to them is having someone who can provide social and moral support. In contrast, boys are more concerned with establishing and asserting their independence and defining their relation to authority. As such, they are more likely to derive high self-esteem from their ability to successfully influence their friends.
Relationships
Peers
Peer groups are especially important during adolescence, a period of development characterized by a dramatic increase in time spent with peers and a decrease in adult supervision. Adolescents also associate with friends of the opposite sex much more than in childhood and tend to identify with larger groups of peers based on shared characteristics. Peer groups offer members the opportunity to develop various social skills like empathy, sharing and leadership.
Romance and Sexual Activity
Romantic relationships tend to increase in prevalence throughout adolescence. The typical duration of relationships increases throughout the teenage years as well. This constant increase in the likelihood of a long-term relationship can be explained by sexual maturation and the development of cognitive skills necessary to maintain a romantic bond, although these skills are not strongly developed until late adolescence. Overall, positive romantic relationships among adolescents can result in long-term benefits. High-quality romantic relationships are associated with higher commitment in early adulthood and are positively associated with self-esteem, self-confidence and social competence.
Gender Differences in Social Interaction
Masculine and feminine individuals generally differ in how they communicate with others.
Learning Objectives
Explain and illustrate gender differences in social interactions
Key Points
- Differences between ” gender cultures ” influence the way that people of different genders communicate. These differences begin at childhood.
- Traditionally, masculine people and feminine people communicate with people of their own gender in different ways.
- Through communication we learn about what qualities and activities our culture prescribes to our sex.
Key Terms
- gender : The socio-cultural phenomenon of the division of people into various categories such as male and female, with each having associated roles, expectations, stereotypes, etc.
- gender culture : The set of behaviors or practices associated with masculinity and femininity.
Social and cultural norms can significantly influence both the expression of gender identity, and the nature of the interactions between genders.
Differences between “gender cultures” influence the way that people of different genders communicate. These differences begin at childhood. Maltz and Broker’s research showed that the games children play contribute to socializing children into masculine and feminine cultures. For example, girls playing house promotes personal relationships, and playing house does not necessarily have fixed rules or objectives. Boys, however, tend to play more competitive team sports with different goals and strategies. These differences as children cause women to operate from assumptions about communication, and use rules for communication that differ significantly from those endorsed by most men.
Gender Differences in Social Interaction
Masculine and feminine cultures and individuals generally differ in how they communicate with others. For example, feminine people tend to self-disclose more often than masculine people, and in more intimate details. Likewise, feminine people tend to communicate more affection, and with greater intimacy and confidence than masculine people. Generally speaking, feminine people communicate more and prioritize communication more than masculine people.
Traditionally, masculine people and feminine people communicate with people of their own gender in different ways. Masculine people form friendships with other masculine people based on common interests, while feminine people build friendships with other feminine people based on mutual support. However, both genders initiate opposite-gender friendships based on the same factors. These factors include proximity, acceptance, effort, communication, common interests, affection and novelty.
Context is very important when determining how we communicate with others. It is important to understand what script it is appropriate to use in each respective relationship. Specifically, understanding how affection is communicated in a given context is extremely important. For example, masculine people expect competition in their friendships.They avoid communicating weakness and vulnerability. They avoid communicating personal and emotional concerns. Masculine people tend to communicate affection by including their friends in activities and exchanging favors. Masculine people tend to communicate with each other shoulder-to-shoulder (e.g., watching sports on a television).
In contrast, feminine people are more likely to communicate weakness and vulnerability. In fact, they may seek out friendships more in these times. For this reason, feminine people often feel closer to their friends than masculine people do. Feminine people tend to value their friends for listening and communicating non-critically, communicating support, communicating feelings of enhanced self-esteem, communicating validation, offering comfort and contributing to personal growth. Feminine people tend to communicate with each other face-to-face (e.g., meeting together to talk over lunch).
Communication and Gender Cultures
A communication culture is a group of people with an existing set of norms regarding how they communicate with each other. These cultures can be categorized as masculine or feminine. Gender cultures are primarily created and sustained by interaction with others. Through communication we learn about what qualities and activities our culture prescribes to our sex. While it is commonly believed that our sex is the root source of differences and how we relate and communicate to others, it is actually gender that plays a larger role. Whole cultures can be broken down into masculine and feminine, each differing in how they get along with others through different styles of communication. Julia T. Wood’s studies explain that “communication produces and reproduces cultural definitions of masculinity and femininity. ” Masculine and feminine cultures differ dramatically in when, how, and why they use communication.
Communication Styles
Deborah Tannen’s studies found these gender differences in communication styles (where men more generally refers to masculine people, and women correspondingly refers to feminine people):
- Men tend to talk more than women in public situations, but women tend to talk more than men at home.
- Women are more inclined to face each other and make eye contact when talking, while men are more likely to look away from each other.
- Men tend to jump from topic to topic, but women tend to talk at length about one topic.
- When listening, women make more noises such as “mm-hmm” and “uh-huh”, while men are more likely to listen silently.
- Women are inclined to express agreement and support, while men are more inclined to debate.
Contributors and Attributions
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2.10: Key Terms Defined
Agricultural density: The number of farmers per unit area of arable land.
Arithmetic density: The population of a country divided by its total land area.
Carrying capacity : The maximum population size that the environment can sustain indefinitely.
Cartogram: map in which some thematic mapping variable—such as population—is substituted for land area or distance.
Cohort: A subset of a population, generally defined by an age range.
Crude birth rate: Total number of live births per 1,000 of a population in a year.
Crude death rate: Total number of deaths per 1,000 of a population in a year.
Demographic transition : The transition from high birth and death rates to lower birth and death rates as a country or region develops.
Dependency ratio: The ratio of those not in the labor force (generally ages 0 to 14 and 65+) and those in the labor force.
Doubling time: The period of time required for a population to double in size.
Ecological Fallacy: Characteristics about the nature of individuals are deduced from inference for the group to which those individuals belong.
Ecumene: The Greek concept of the habitable part of the Earth
Infant mortality rate: The number of infant deaths that occur for every 1,000 live births.
Life expectancy: The number of years that one is expected to live as determined by statistics.
Morbidity: The state of being diseased or unhealthy within a population.
Mortality: The number of people who have died within a population.
Overpopulation: A condition in which a place has outstripped its ability to provide for its own needs.
Physiological density: The number of people per unit area of arable land.
Population density: A measurement of population per areal unit, such as the world, a region, a country or other area.
Population momentum: The tendency for population growth to continue due to high concentrations of people in the childbearing years.
Population projection : An estimate of future population.
Population pyramid: Graphical illustration that shows the distribution of various age groups in a population.
Rate of natural increase: The crude birth rate minus the crude death rate. This rate excludes the effect of migration.
Replacement level: The average number of children a woman needs to have to ensure the population replaces itself. The number is roughly 2.1.
Total fertility rate : The average number of children that would be born to a woman over her lifetime.


15.13: Test Yourself
1. Where are the organs that sense pain, pressure and temperature found?
2. Which sense organ responds to chemicals in the air?
3. Match the words in the list below with the following descriptions.
- optic nerve | choroid | cornea | aqueous humor | retina | cones | iris | vitreous humour | sclera | lens
- a) Focuses light rays on the retina.
- b) Respond to colour and detail.
- c) Outer coat of the eyeball.
- d) Carries nerve impulses from the retina to the brain.
- e) The chamber behind the lens is filled with this.
- f) This layer of the eyeball reflects light in nocturnal animals like the cat.
- g) This is the transparent window at the front of the eye.
- h) This constricts in bright light to reduce the amount of light entering the eye.
- i) The light rays are focused on here by the lens and cornea.

4. Add the following labels to the diagram of the ear below.
- pinna | Eustachian tube | cochlea | tympanic membrane | external ear canal | ear ossicles | semicircular canals
5. What is the role of the Eustachian tube?
6. What do the ear ossicles do?
7. What is the role of the semicircular canals?


1.1: Developmental Theory
Socialization
Developmental Overview
This section will introduce human development for some and review human development foundations for others. Human development is divided into 3 main areas: Physical, Cognitive, and Affective. Together, these areas address the development of the whole child.
- Physical-motor development – this includes our gross motor, fine motor, and perceptual-motor development.
- Cognitive or intellectual development – this includes our thoughts and how our brain processes information, as well as how we utilize language so that we can communicate with one another.
- Affective development – this includes our emotions, social interactions, personality, creativity, spirituality, and the relationships we have with ourselves and others.
All three areas of development are of critical importance in how we support the whole child. For example, if we are more concerned about a child’s cognitive functioning we may neglect to give attention to their affective development. We know that when a child feels good about themselves and their capabilities, they are often able to take the required risks to learn about something new. Likewise, if a child is able to use their body to learn, that experience helps to elevate it to their brain. Below is a image of a child who is learning to walk. All areas of development is being impacted during this task. Additionally, as a society we value independence and caregivers work to facilitate the acquisition of these skills.
“If it isn’t in the body, it can’t be in the brain.”
- Bev Bos
Developmental Theories
A theory is defined as “a supposition, or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained, a set of principles on which the practice of an activity is based.”
The theories we chose to include in this text form the underlying “principles” that guide us in the decisions we make about the children in our care, as well as provide us with insight on how to best support children as they learn, grow, and develop. The theories that have been selected were proposed by scientists and theorists who studied human development extensively. Each, with their own unique hypothesis, set out to examine and explain development by collecting data through observations/experiments. The theorists we selected, strived to answer pertinent questions about how we develop and become who we are. Some sought to explain why we do what we do, while others studied when we should achieve certain skills. Here are a few of the questions developmental theorists have considered:
- Is development due to maturation or due to experience? This is often described as the nature versus nurture debate . Theorists who side with nature propose that development stems from innate genetics or heredity. It is believed that as soon as we are conceived, we are wired with certain dispositions and characteristics that dictate our growth and development. Theorists who side with nurture claim that it is the physical and temporal experiences or environment that shape and influence our development. It is thought that our environment - our socio-economic status, the neighborhood we grow up in, and the schools we attend, along with our parents’ values and religious upbringing - that impact our growth and development. Many experts feel it is no longer an “either nature OR nurture” debate but rather a matter of degree; which influences development more?
- Does one develop gradually or does one undergo specific changes during distinct time frames? This is considered the continuous or discontinuous debate. On one hand, some theorists propose that growth and development are continuous; it is a slow and gradual transition that occurs over time, much like an acorn growing into a giant oak tree. While on the other hand, there are theorists that consider growth and development to be discontinuous; which suggests that we become different organisms altogether as we transition from one stage of development to another, similar to a caterpillar turning into a butterfly.
- Is behavior shaped by individual internal processes or by the role of society in shaping behavior?
Socialization is the means by which human infants begin to acquire the skills necessary to perform as functioning members of their society.
-What skills did you acquire to become a successful adult? Who and what was instrumental in shaping you to fit into society?
As suggested earlier, not only do theories help to explain key components of human development, theories also provide practitioners with valuable insight that can be utilized to support a child’s learning, growth, and development. At this time, we would like to mention that although theories are based on notable scientific discoveries, it is necessary to emphasize the following:
- No one theory exclusively explains everything about a child’s development.
- Theories are designed to help us make educated guesses about children’s development
- Each theory focuses on a different aspect of human development
- Theories often build on previous theoretical concepts and may seek to expand ideals or explore new facets.
- Theories may not be generally applied to all diverse experiences