Exam 2 Q's

Question 1

1. A chemoorganoheterotroph growing on citrate is aerobically respiring using an electron transport chain with a P/O ratio of 0.5. How many molecules of ATP are made when electrons from 20 NADH are passed through this chain?
   a. 5
   b. 10
   c. 20
   d. 40

Answer 1

b. 10

Question 2

2. If a heterotroph is anaerobically respiring, which of the following statements is true?
   a. The cell runs the reverse ATPase.
   b. The cell obtains carbon from CO2.
   c. The cell consumes oxygen as a terminal electron acceptor.
   d. The cell uses an electron transport chain to make proton motive force.

Answer 2

d. The cell uses an electron transport chain to make proton motive force.

Question 3

3. If the growth rate of an organism decreases 4 fold, the generation time _________.
   a. remains constant.
   b. increases 4 fold.
   c. decreases 4 fold.
   d. cannot be predicted.

Answer 3

b. increases 4 fold

Question 4

4. Which of the following transport systems is unable concentrate substrate on the inside of the cell?
   a. facilitated diffusion
   b. primary active transport
   c. secondary active transport
   d. none of the above

Answer 4

a. facilitated diffusion

Question 5

5. Which of the following statements is true for both PTS transport and ABC-type transport?
   a. Transport chemically modifies the substrate during uptake.
   b. Transport requires specific proteins for each substrate.
   c. Transport does not change the substrate gradient. d. Transport is powered by ATP hydrolysis.

Answer 5

b. Transport requires specific proteins for each substrate.

Question 6

6. Which of the following statements concerning secondary active transport is not true?
   a. It uses ATP as an energy source.
   b. It requires a membrane protein channel.
   c. It requires an energetically favorable gradient.
   d. It can concentrate substrates on the inside of the cell.

Answer 6

a. It uses ATP as an energy source.

Question 7

7. The kinetics of facilitated diffusion versus passive diffusion are shown in the graph to the right. Why does the rate of facilitated diffusion plateau at high substrate concentration?
   a. transport proteins become limiting
   b. substrate becomes limiting
   c. protons become limiting
   d. ATP becomes limiting

Answer 7

a. transport proteins become limiting