review answers - Hyper tonic-“more” in regards to the...

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How are membranes adjusted for different temperatures? A membrane remains fluid as temperature decreases, until finally the phospholipids settle into a closely packed arrangement and the membrane solidifies. The membrane remains fluid to a lower temperature if it is rich in phospholipids with unsaturated hydrocarbon tails. Membranes must be fluid to work properly. Kinks keep molecules from packing together. What types of molecules can move across the membrane? Gases, steroid hormones, and water Simple Diffusion - Down the Concentration gradient with no help. Gives off heat. Facilitated Diffusion - Many Hydrophilic substances diffuse through membranes with the assistance of transport proteins, either channel or carrier proteins. Down the gradient, not against it. Active Transport - Some transport proteins act as pumps, moving substances across a membrane against their concentration gradients. Energy for this work is usually supplied by ATP. Tonicity- the ability of a solution to cause a cell to gain or lose water.
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Unformatted text preview: Hyper tonic-“more” in regards to the solution. More salts, so a cell would shrivel and die. (Freshwater bony fish is hypertonic to freshwater.) Hypo tonic-“less” in regards to the solution. Less salts, meaning more water, so the cell would absorb water faster than it could take it out, so it would explode. (Marine bony fish are hypotonic to seawater.) Iso tonic-“same”, if an animal cell is placed into an isotonic solution, there will be no net movement of water across the membrane. Because, water would move in, at the same rate it moved out. (marine invertebrates are isotonic w/ seawater. Accumulates free amino acids to match the tonicity of sea water.) (Sharks and rays are isotonic w/ seawater. Accumulate .5m urea.) Osmosis- diffusion of water across a selectively impermeable membrane, from a region of lower solute concentration to a region of higher solute concentration....
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This note was uploaded on 04/07/2008 for the course PHYSICS AN 1100, 2101 taught by Professor Giammanico during the Spring '07 term at LSU.

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