AP-Micro Microbiology: Microbial Metabolism 3

Question 1

A microorganism produces acetone and butanol as end products of fermentation. Which pathway is it most likely using?

Accepted Answer

Acetone-butanol-ethanol (ABE) fermentation

Answer

ABE fermentation is characteristic of Clostridium species, which produce acetone, butanol, and ethanol as major end products.

Question 2

Which of the following best describes anoxygenic photosynthesis in purple sulfur bacteria?

Accepted Answer

Uses H2S as electron donor, releases sulfur, no O2 produced

Answer

Purple sulfur bacteria use H2S as their electron donor, depositing elemental sulfur, and do not produce oxygen as a byproduct.

Question 3

The Entner-Doudoroff (ED) pathway produces which net products per glucose (compared to glycolysis)?

Accepted Answer

1 ATP, 1 NADH, 1 NADPH, 2 pyruvate

Answer

The ED pathway yields only 1 ATP, 1 NADH, and 1 NADPH per glucose while still producing 2 pyruvate molecules.

Question 4

Catabolite repression in E. coli ensures that glucose is preferentially metabolized over lactose primarily through:

Accepted Answer

Low cAMP levels preventing CAP activation of the lac operon

Answer

When glucose is present, adenylyl cyclase activity is low, keeping cAMP levels low so CAP cannot activate the lac operon.

Question 5

During beta-oxidation of a 16-carbon saturated fatty acid, how many acetyl-CoA molecules are produced?

Accepted Answer

8

Answer

A 16-carbon fatty acid undergoes 7 rounds of beta-oxidation to yield 8 acetyl-CoA, 7 NADH, and 7 FADH2.

AP Practice Test