Molecular Cell Biology 8th Edition By Harvey Lodish – Test Bank

1. The partition coefficient K, the equilibrium constant for partitioning between oil and water, for butyric acid is about 10–2, and for 1,4-butanediol it is about 10–4. You add liposomes containing only water to a solution with an initial concentration of 1 mM butyric acid and 100 mM 1,4-butanediol outside the liposomes. What is the relative rate of diffusion of the two substances into the liposome interior?
a. Butyric acid diffuses into the liposome 100-fold faster than butanediol.
b. The two diffuse into the liposome at equal rates.
c. Butanediol diffuses into the liposome 100-fold faster than butanediol.
d. Not enough information is provided to permit an answer.

Ans: b
Question Type: Multiple Choice
Chapter: 11
Blooms: Analyzing
Difficulty: Difficult

2. Classes of membrane transport proteins include all of the following EXCEPT:
a. ATP-powered pumps.
b. ion channels.
c. protein translocons.
d. transporters.

Ans: c
Question Type: Multiple Choice
Chapter: 11
Blooms: Understanding
Difficulty: Easy

3. The glucose uniporter GLUT1 has a Km of 1.5 mM for D-glucose and 30 mM for D-galactose. At a concentration of 5 mM for each, what is the rate of glucose transport relative to galactose transport? The Vmax may be assumed to be the same for both.
a. 3.7-fold slower
b. equal
c. 5.5-fold faster
d. 20-fold faster

Ans: c
Question Type: Multiple Choice
Chapter: 11
Blooms: Analyzing
Difficulty: Moderate

4. Both ethanol and glycine are small molecules of approximately equal molecular weight. However, the membrane is much more permeable to ethanol than glycine. What accounts for the large difference in membrane permeability between ethanol and glycine?
Ans: Ethanol is a small alcohol; glycine is a small amino acid. Glycine, like all amino acids, is a zwitterion. At neutral pH, the amino group of glycine is positively charged and the carboxyl group is negatively charged. Charged groups are impermeable to lipid bilayers.
Question Type: Essay
Chapter: 11
Application
Difficulty: Moderate

5. In a laboratory activity, red-labeled glucose, blue-labeled water, and green-labeled ethanol are added to a solution placed over an artificial, pure phospholipid membrane. Which colors will be observed on the other side of the membrane after 10 minutes?
a. red
b. blue
c. green
d. b and c

Ans: d
Multiple select
Chapter: 11
Blooms: Understanding
Difficulty: Easy

6. In which of the following cases is energy NOT needed for transmembrane transport?
a. Lysine moves into the cell against its concentration gradient via the Na+/lysine symporter.
b. Potassium ions (K+) move out of the cell down the K+ concentration gradient via potassium channels.
c. Glucose moves into the cell down its concentration gradient via a glucose uniporter.
d. The second and third answers are correct.
e. all of the above

Ans: d
Question Type: Multiple Choice
Chapter: 11
Blooms: Understanding
Difficulty: Moderate

Section 11.2

7. How does uniport transport compare with simple diffusion?
a. Similar to simple diffusion, uniport transport is nonspecific.
b. Uniport transport is slower but more specific than simple diffusion.
c. Uniport transport is much faster and more specific than simple diffusion.
d. Simple diffusion is reversible but uniport transport is not.

Ans: c
Question Type: Multiple Choice
Chapter: 11
Blooms: Understanding
Difficulty: Moderate

8. Aquaporins are:
a. -barrel proteins in the outer membrane of bacteria.
b. ABC proteins.
c. symporters.
d. water channels.

Ans: d
Question Type: Multiple Choice
Chapter: 11
Blooms: Remembering
Difficulty: Easy

9. When computing the osmotic pressure that must be placed across the membrane to stop the flow of water, what is the glucose osmotic equivalent of 1 M CaCl2?
a. 1 M
b. 2 M
c. 3 M
d. 4 M

Ans: c
Question Type: Multiple Choice
Chapter: 11
Application
Difficulty: Moderate

10. Describe how aquaporins facilitate the movement of water across the plasma membrane.

Ans: Aquaporins are water-channel proteins that specifically increase the permeability of biomembranes to water. The level of aquaporin 2 is rate-limiting for water transport by the kidney and is essential for resorption of water in the kidney.
Question Type: Essay
Chapter: 11
Blooms: Understanding
Difficulty: Easy