Protein charged molecules cannot diffuse. Membrane proteins contain internal channels that allow such molecules to enter and exit the cell. Many ion channel proteins are specialized to select for only a particular ion; for example, potassium and sodium channels often discriminate for only one of the two ions. Structural proteins confer stiffness and rigidity to otherwise-fluid biological components. Most structural proteins are fibrous proteins; for example, collagen and elastin are critical components of connective tissue such as cartilage, and keratin is found in hard or filamentous structures such as hair, nails, feathers, hooves, and some animal shells. Some globular proteins can
Collagen the form of dietary supplement or functional foods and beverages with the intent to aid joint and bone health and enhance skin health. Hydrolyzed collagen has a much smaller molecular weight in comparison to native collagen or gelatin, study suggests that more than 90% of hydrolyzed collagen is digested and available as small peptides in the blood stream within one hour. From the blood, the peptides (containing hydroxyproline) are transported into the target tissues (e.g., skin, bones, and cartilage), where the peptides act as building blocks for local cells and help boost the production of new collagen fibers. Collagen is