Chapter 5

Membranes Fluid phospholipid bilayer? Transmembrane proteins/integral membrane proteins [transport molecules/messages in/out of cell]; have hydrophobic regions that cross the bilayer ? Interior protein network [shape of cell, anchor proteins to specific sites]? Cell surface markers ["self" recognition, tissue recognition? Unequal distribution of proteins? Saturated fats make the membrane less fluid because they pack together well while unsaturated fats make the membrane more fluid--the kinks made by the double bond keep them from packing close together ? High temperature makes a membrane more fluid? Low temperature makes a membrane less fluid? Cholesterol can increase or decrease membrane fluidity depending on the temperature? Proteins Transporters: let substances in/out? Enzymes: catalyze reactions on the inside of cells? Cell surface receptors: receive chemical messages? Cell surface identity markers: name tags? Cell-to-cell adhesion proteins: allows cells to stick together? Attachments to the cytoskeleton: cannot move? Proteins embedded in the membrane have at least one hydrophobic region that anchors it? Passive Transport At high concentrations, the rate of transport levels off [called saturation]? Carrier proteins bind to the molecule they transport ? Simple diffusion through channel proteins, carrier proteins, ion channels [selectively permeable]? Osmosis Hypertonic: the solution with the lower concentration? Hypotonic: the solution with the higher concentration? Isotonic: solutions with equal concentrations? Water diffuses out of a cell in a hypertonic solution? Water diffuses from high concentrations to low concentrations ? Uniporters: transport a single type of molecule? Symporters: transport 2 molecules in the same direction? Antiporters: transport 2 molecules in opposite directions ? Sodium-postassium pump Active Transport Chapter 5 Tuesday, February 17, 2009 11:30 PM Biology Page 1 Transports Na+ and K+ from areas of low concentration to areas of high concentration? 3 Na+ leave the cell and 2K+ enter with each cycle? Sodium-postassium pump? Coupled transport: the energy released as one molecule moves down its concentration gradient is used to move another molecule against its concentration gradient ? Countertransport: ? Phagocytosis: if the material is solid? Pinocytosis: if the material is liquid? Receptor-mediated endocytosis:? Endocytosis: plasma membrane envelopes food particles and fluids Exocytosis: the discharge of material from vesicles at the cell surface Biology Page 2