LSU Bio 1201 Exam 2 Questions With Verified Answers

LSU Bio 1201 E xam 2 Questio ns With Verified Answers why are membranes called phospholipid bilay ers? - answer✔✔phospholipids have hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2 layers what is meant by fluid mosaic? - answer✔✔Mosaic of proteins drifting laterally in fluid bilayer of phospholipids how are membranes adju sted for different temperatures? - answer✔✔membrane fluidity adjusted by changing the ratio of unsaturated to saturated fatty acids how do the relative amounts of saturated and unsaturated fats change? - answer✔✔if you are in a cold environment you want mo re saturated fats for your membranes to be fluid; warm environment you want more saturated fats to make your membranes more solid what is meant by membrane fluidity? - answer✔✔not too solid, not too fluid why is fluidity an important property? - answer✔✔preserves membrane function Henrique and Hanson performed experiments with pigs and examined the effects on the relative amounts of saturated and unsaturated fats. What did they find? - answer✔✔found that membrane fluidity can acclimate to temperature; pigs raised wearing underwear i n a hot room had subcutaneous fats with higher melting point what types of molecules can move easily across the membrane? - answer✔✔small nonpolar molecules, gases, steroid hormones, and water what is simple diffusion? - answer✔✔down the concentration grad ient; does not require supplied energy; does not use a carrier molecule what is facilitated diffusion? - answer✔✔down the concentration gradient; employs carrier molecule; does not require supplied energy what is active transport? - answer✔✔work must me do ne; must use supplied energy; employs carrier molecule for which transport processes are carrier molecules involved? - answer✔✔facilitated diffusion and active transport which transport processes require the input of additional energy? - answer✔✔active tra nsport what is a semi -permeable barrier? - answer✔✔only some types of molecules pass through when equilibrium is reached in diffusion: does movement of molecules stop? - answer✔✔no when equilibrium is reached in diffusion: does the net movement of molecule s stop? - answer✔✔yes what is meant by hypertonic? - answer✔✔lower water potential; more solutes dissolved; tend to gain water via osmosis what is meant by hypertonic? - answer✔✔higher water potential; fewer solutes dissolved; will tend to lose water via o smosis isotonic - answer✔✔equivalent water potential; equal number of solutes; no note movement of water in which direction does water flow? - answer✔✔osmosis and the direction of net water movement what are aquaporins? - answer✔✔channel proteins which fac ilitate water diffusion through the membrane marine bony fish are...? - answer✔✔hypotonic to seawater how do enzymes work? - answer✔✔they position the reactants in a conformation more favorable for the chemical reaction to occur what aspects of the energet ics do enzymes change? - answer✔✔enzymes lower activation energy barrier ΔG⧧ what aspects of energetics do enzymes not affect? - answer✔✔they do not reverse an energetically unfavorable reactions; they do not make a reaction go uphill how are substrates lu red into the active site? - answer✔✔positively charged arginine sidechain lures the negatively charged substrate into the active site what are the analogs to these characters in the binding of substrates to enzymes? - answer✔✔Siren song= positively charged arginine sidechain Negatively charged substrate= Odysseus' men Circe= active site how do temperature changes affect the rates of reactions catalyzed by enzymes? - answer✔✔temperature is a measure of how many molecules will have achieved activation energy; low temp= low energy associated with molecule