PSL300H1 Lecture Notes - Kinetic Energy, Clathrin, Exocytosis
Document Summary
Permeability of the membrane depends on molecular size, lipid solubility, and charge. Fatty acid tails help determine the properties. Polar end (head) is glycerol + phosphate (hydrophilic) + choline/serine often charged. Nonpolar end is 2 long fatty acid chains (hydrophobic); one saturated, one polyunsaturated. Cholesterol is inserted among fa chains to stabilize the membrane + decrease permeability. Necessary for efficient carrier and channel protein function. Cholesterol stabilizes membrane and prevents diffusion of polar molecules across it. Fluidity of a membrane is reduced by aging and a poor diet: aging causes a loss of cholesterol membrane can become leaky. Selective transporters (carriers) of molecules across a membrane. Membrane-spanning proteins it is most common for a protein to cross the membrane 6-7 times. The part of the protein that crosses the membrane is usually helical. Matrix of long carbohydrate filaments; they fill extracellular space, slowing diffusion. Net negative charge (polarized) attract positive ions (ca2+)
