AP-Micro (Microbiology) Microbial Metabolism 1 — Questions and Answers
Question 1: Which molecule acts as the primary energy carrier in microbial cells?
- Glucose
- ATP (Adenosine Triphosphate) (Correct answer)
- NADH
- Pyruvate
Correct answer: ATP (Adenosine Triphosphate)
ATP (Adenosine Triphosphate) is universally recognized as the primary energy currency of the cell, including microbial cells. It stores and transfers energy released from catabolic reactions to power anabolic processes and other cellular activities. While glucose is an energy source and NADH carries electrons, ATP directly provides the readily usable energy for most cellular functions.
Question 2: In anaerobic respiration, what acts as the terminal electron acceptor?
- Oxygen
- Nitrate (Correct answer)
- Glucose
- Water
Correct answer: Nitrate
In anaerobic respiration, oxygen is not available to serve as the terminal electron acceptor. Instead, microorganisms utilize various inorganic molecules like nitrate, sulfate, or carbonate to accept electrons at the end of their electron transport chain. This process allows for the regeneration of NAD+ and continued ATP production in the absence of oxygen.
Question 3: What is the primary purpose of fermentation in microorganisms?
- Produce ATP directly
- Regenerate NAD+ for glycolysis (Correct answer)
- Break down proteins
- Generate oxygen
Correct answer: Regenerate NAD+ for glycolysis
Fermentation is an anaerobic process that occurs after glycolysis. Its primary purpose is not to produce ATP directly, but to regenerate NAD+ from NADH. This regeneration is crucial because NAD+ is a coenzyme required for glycolysis to continue, allowing the cell to produce a small amount of ATP even without oxygen or an external electron acceptor.
Question 4: Which process generates the most ATP in microbial metabolism?
- Glycolysis
- Fermentation
- Krebs Cycle (Citric Acid Cycle)
- Oxidative Phosphorylation (Correct answer)
Correct answer: Oxidative Phosphorylation
Oxidative phosphorylation is the metabolic pathway that generates the vast majority of ATP in aerobic respiration. It involves the electron transport chain and chemiosmosis, where the energy from electrons is used to pump protons, creating a gradient that drives ATP synthase. While glycolysis and the Krebs cycle produce some ATP, oxidative phosphorylation is by far the most efficient ATP-generating process.
Question 5: What is the end product of glycolysis?
- Acetyl-CoA
- Pyruvate (Correct answer)
- NADH
- ATP
Correct answer: Pyruvate
Glycolysis is the initial metabolic pathway that breaks down one molecule of glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon compound). This process also yields a net gain of ATP and NADH. Pyruvate then proceeds to further metabolic pathways like the Krebs cycle or fermentation, depending on the presence of oxygen.
AP-Micro (Microbiology) Microbial Metabolism 1
Which molecule acts as the primary energy carrier in microbial cells?