Microbiology: Microbial Metabolism Flashcards

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

Answer: Acetone-butanol-ethanol (ABE) fermentation

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

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

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

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

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

Answer: 1 ATP, 1 NADH, 1 NADPH, 2 pyruvate

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

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

Answer: Low cAMP levels preventing CAP activation of the lac operon

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

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

Answer: 8

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

Which enzyme catalyzes the committed step of the pentose phosphate pathway?

Answer: Glucose-6-phosphate dehydrogenase

Glucose-6-phosphate dehydrogenase oxidizes glucose-6-phosphate to 6-phosphogluconolactone, committing the molecule to the pentose phosphate pathway.

What type of metabolism does an organism exhibit if it can grow under both aerobic and anaerobic conditions but grows more efficiently with oxygen?

Answer: Facultative anaerobe

Facultative anaerobes can perform both aerobic respiration and fermentation/anaerobic respiration, but prefer oxygen for its higher ATP yield.