LIFE 102 Lecture Notes - Passive Transport, Osmosis, Glycolipid
Document Summary
As temperatures cool, membranes switch from a fluid state to a solid state. The temperature at which a membrane solidifies depends on the types of lipids. Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids. Membranes must be fluid to work properly; they are usually about as fluid as salad oil. The steroid cholesterol has different effects on membrane fluidity at different temperatures. At warm temperatures, cholesterol restrains movement of phospholipids. At cool temperatures, it maintains fluidity by preventing tight packing. A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer. Proteins determine most of the membrane s specific functions. Peripheral proteins are bound to the surface of the membrane. Integral proteins that span the membrane are called transmembrane proteins. The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids, often coiled into alpha helices.
