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Unformatted text preview: . Phospholipids: a) consist of a polar, hydrophilic, phosphate-bearing head and two non-polar, hydrophobic, fatty acid tails. b) are aligned in a lipid bilayer c) serve as a carrier molecule d) both [a] and [b] are correct e) all of the above are correct Which of the following statements concerning the plasma membrane is correct? a) It is more permeable to K+ than Na+ at resting state b) Serves as a barrier to the passage of water soluble substances through the membrane c) It contains proteins, cholesterol and carbohydrate chains d) All of these are correct e) None of these are correct Which of the following is not a function of membrane proteins? a) They serve as channels b) They determine the fluidity of the membrane c) They serve as carriers d) They serve as receptor sites e) They can have enzymatic activity . If a cell were exposed to a hypertonic solution which of the following would occur? a) Water would move into the cell causing the cell to expand in volume b) Water would move out of the cell causing the cell to shrink in volume c) The net movement of water would be neither in nor out of the cell Selective permeability of the membrane is primarily determined by: answer wrong a) membrane phospholipids b) how much cholesterol is present c) the number and type of membrane proteins d) the charge of the membrane e) all of these answers Carrier-mediated transport: a) involves a specific membrane protein that serves as a carrier molecule b) always moves substances against a concentration gradient c) always requires energy expenditure d) both [a] and [c] e) All of these are correct . Which increases the rate of diffusion for a substance through a membrane? a) decreasing the concentration gradient b) increasing the molecular weight of the substance c) decreasing the permeability of the membrane d) increasing the surface area of the membrane e) increasing the thickness of the membrane Which of the following descriptions of movement of molecules across the plasma membrane is correct? a) If two similar molecules can both combine with the same carrier, the presence of one of these molecules decreases the rate of entry of the other. b) In simple diffusion, the rate of transport of a molecule is directly proportional to the molecule's extracellular concentration. c) When a carrier becomes saturated, the maximum rate of transport is reached. d) Two of these statements are correct e) All of these statements are correct Which of the following substances is most likely to passively diffuse across the plasma membrane?...
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