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Problem 1
In what way do the membranes of a eukaryotic cell vary? a. Phospholipids are found only in certain membranes. b. Certain proteins are unique to each membrane. c. Only certain membranes of the cell are selectively permeable. d. Only certain membranes are constructed from amphipathic molecules.
Problem 2
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly a. spread in a continuous layer over the inner and outer surfaces of the membrane. b. confined to the hydrophobic interior of the membrane. c. embedded in a lipid bilayer. d. randomly oriented in the membrane, with no fixed inside-outside polarity.
Problem 3
Which of the following factors would tend to increase membrane fluidity? a. a greater proportion of unsaturated phospholipids b. a greater proportion of saturated phospholipids c. a lower temperature d. a relatively high protein content in the membrane
Problem 4
Which of the following processes includes all the others? a. osmosis b. diffusion of a solute across a membrane c. passive transport d. transport of an ion down its electrochemical gradient
Problem 5
Based on Figure 7.18, which of these experimental treatments would increase the rate of sucrose transport into a plant cell? a. decreasing extracellular sucrose concentration b. decreasing extracellular pH c. decreasing cytoplasmic pH d. adding a substance that makes the membrane more permeable to hydrogen ions
Problem 6
DRAW IT An artificial 'cell' consisting of an aqueous solution enclosed in a selectively permeable membrane is immersed in a beaker containing a different solution, the 'environment,' as shown in the accompanying diagram. The membrane is permeable to water and to the simple sugars glucose and fructose but impermeable to the disaccharide sucrose. a. Draw solid arrows to indicate the net movement of solutes into and/or out of the cell. b. Is the solution outside the cell isotonic, hypotonic, or hypertonic? c. Draw a dashed arrow to show the net osmosis, if any. d. Will the artificial cell become more flaccid, more turgid, or stay the same? e. Eventually, will the two solutions have the same or different solute concentrations?
