B.2.1 Membranes and transport

Notes

B.2.1 Membranes and transport 1. Structure of the Cell Membrane (Phospholipid Bilayer) Made of phospholipids, cholesterol, and proteins. Phospholipids are amphipathic: Hydrophilic head (phosphate): faces water (outside/inside cell). Hydrophobic tail (fatty acid chains): faces inward, away from water. Arranged as a bilayer: tails inward, heads outward. Maintains a semi-permeable barrier between the cell and its environment . 2. Membrane Components and Properties Cholesterol: Stabilizes membrane fluidity. Prevents membrane from becoming too fluid or too rigid. Membrane proteins: Integral proteins: embedded in the membrane (some span entire membrane = transmembrane). Transport molecules across the membrane Hydrophobic region inside membrane. Hydrophilic regions exposed to cytoplasm or extracellular fluid. Peripheral proteins: loosely attached to the surface of the membrane or integral proteins. Enzymes, link membrane to cytoskeleton, or signaling cascades Hydrophilic and interact with phosphate heads or other proteins. 3. Amphipathic Nature of Phospholipids Amphipathic = has both hydrophilic and hydrophobic regions. Ensures the correct orientation of phospholipids in bilayer. Crea...