Chapter 7: Membrane Structure and Function s1

Chapter 7: Membrane Structure and Function Name Date AP Biology Mr. Mennecke

1. In what way do the various membranes of a eukaryotic cell differ? a. Phospholipids are only found in certain membranes. b. Certain proteins are unique to each membrane depending on the species. c. Only certain membranes of the cell are selectively permeable. d. Some membranes have hydrophilic surfaces exposed to the cytoplasm, while others have hydrophobic surfaces facing the cytoplasm.

2. According to the fluid mosaic model of membrane structure, proteins of the membrane are a. spread in a continuous layer over the inner and outer surfaces of the membrane b. confined to the hydrophobic core of the membrane c. embedded in a lipid bilayer d. free to depart from the fluid membrane and dissolve in the surrounding solution

3. Which of the following factors would tend to increase membrane fluidity? a. a greater proportion of unsaturated phospholipids b. a lower temperature c. a relatively high protein content in the membrane d. a greater proportion of relatively large glycolipids compared to lipids having smaller molecular weight

4. Which of the following processes include all others in the list? a. diffusion of a solute across a membrane b. facilitated diffusion c. passive transport d. transport of an ion down its electrochemical gradient

Questions 5-9: An artificial cell with an aqueous solution enclosed in a selectively permeable membrane has just been immersed in a beaker containing a different solution.

The membrane is permeable to water and to the simple sugars glucose & fructose but completely impermeable to the disaccharide sucrose.

“Environment” 5. Which solute(s) will exhibit a net diffusion “Cell” .01 M sucrose into the cell? .03 M sucrose .01 M glucose .02 M glucose .01 M fructose 6. Which solute(s) will exhibit a net diffusion out of the cell?

7. Which solution- the cell contents or the environment- is hypertonic?

8. In which direction will there be a net osmotic movement of water?

9. After the cell is placed into the beaker, which of the following changes would occur? a. The artificial cell would become more flaccid. b. The artificial cell would become more turgid. c. The overall free energy stored in the system would increase. d. The membrane potential would decrease. Chapter 7: Membrane Structure and Function 10. Define the following: a. phagocytosis

b. pinocytosis

c. endocytosis

d. exocytosis

e. electrochemical gradient

f. facilitated diffusion

g. gated channels

h. ATP

11. A cell is immersed into an open beaker of sucrose long enough to reach equilibrium with its environment. The molarity of the surrounding sucrose solution is 0.5M. To convert molarity to solute potential in bars, use the formula: S = - ( i CRT ) where i = ionization constant (assume that is 1) C=molar concentration (given above) R = pressure constant (R=0.0831 liter bars/mole K) T = temperature in K (room temp is about 293K)

a. Calculate the solute potential of the surrounding solution.

b. Find the water potential of the surrounding solution, assuming the pressure potential is now zero.

c. What is the water potential of the cytoplasm of the cell?

d. True, false, or not enough information: The cell’s molar concentration is equal to the molar concentration of the surrounding solution.