Chloride Content by Weight of Concrete. Q.: For corrosion protection, ACI 318-95, Building Code Requirements for Structural Concrete, specifies maximum water-soluble chloride ion in concrete as percent by weight of cement. What are acceptable levels when measuring chloride-ion content in existing concreteâspecifically, by weight of the concrete sample?
Plasma membranes are selectively permeable, regulating the cellâs molecular traffic. Hydrophobic (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and. pass through the membrane rapidly. Polar molecules, such as sugars, do not cross the membrane easily. Transport Membranes Transport proteins allow passage of hydrophilic substances across the membrane.
Small nonpolar molecules such as molecular oxygen, carbon dioxide and molecules consisting of mostly hydrocarbons move through the membrane easily while polar molecules do not. Examples of polar molecules are monosaccharides, ions, AAs, and water. Large biological molecules such as proteins are way too large to cross the membrane. These large molecules are secreted from cells via exocytosis and frequently enter the cell via endocytosis..