DAT - Dental Admission Biology: Cellular Metabolism Questions and Answers 1 — Questions and Answers
Question 1: A scientist is studying a facultative anaerobe. Under which condition would the organism produce the most ATP per molecule of glucose?
- In the presence of oxygen (Correct answer)
- In the absence of oxygen, via lactic acid fermentation
- In the absence of oxygen, via alcohol fermentation
- The ATP yield is the same regardless of oxygen presence
Correct answer: In the presence of oxygen
Aerobic respiration, which occurs in the presence of oxygen, yields significantly more ATP than anaerobic pathways like fermentation. The complete oxidation of glucose through glycolysis, the Krebs cycle, and oxidative phosphorylation can produce approximately 32-38 ATP, whereas fermentation produces only a net of 2 ATP from glycolysis.
Question 2: Which of the following correctly pairs a metabolic process with its primary cellular location in eukaryotes?
- Krebs Cycle - Mitochondrial Matrix (Correct answer)
- Glycolysis - Mitochondrial Inner Membrane
- Electron Transport Chain - Cytoplasm
- Fermentation - Mitochondrial Matrix
Correct answer: Krebs Cycle - Mitochondrial Matrix
The Krebs Cycle (also known as the citric acid cycle) occurs in the mitochondrial matrix. Glycolysis takes place in the cytoplasm, the electron transport chain is located on the inner mitochondrial membrane, and fermentation also occurs in the cytoplasm.
Question 3: During strenuous exercise, muscle cells may switch to anaerobic respiration. What is the primary purpose of converting pyruvate to lactate in this process?
- To produce additional ATP through substrate-level phosphorylation
- To directly generate more glucose for the muscles
- To regenerate NAD+ from NADH (Correct answer)
- To shuttle electrons directly to the electron transport chain
Correct answer: To regenerate NAD+ from NADH
The primary purpose of lactic acid fermentation is to regenerate NAD+ from the NADH produced during glycolysis. This allows glycolysis to continue producing a small amount of ATP even in the absence of oxygen, which is required for the electron transport chain to function and regenerate NAD+ aerobically.
Question 4: A patient is found to have a genetic disorder that inactivates the enzyme phosphofructokinase-1 (PFK-1), a key regulatory enzyme in glycolysis. Which of the following metabolic consequences would be expected?
- Increased rate of gluconeogenesis (Correct answer)
- Accelerated breakdown of glucose to pyruvate
- Accumulation of fructose-1,6-bisphosphate
- Decreased levels of glucose-6-phosphate
Correct answer: Increased rate of gluconeogenesis
PFK-1 is a key irreversible enzyme in glycolysis. Its inactivation would halt glycolysis, leading to a cellular energy deficit. To compensate and maintain blood glucose levels, the body would upregulate gluconeogenesis, the pathway that synthesizes glucose from non-carbohydrate precursors. The breakdown of glucose would decrease, fructose-1,6-bisphosphate levels would drop (as it's the product of PFK-1), and glucose-6-phosphate would likely accumulate as it cannot proceed down the glycolytic pathway.
Question 5: In photosynthesis, the light-independent reactions (Calvin cycle) utilize which products from the light-dependent reactions?
- Water and photons
- Oxygen and glucose
- ADP and NADP+
- ATP and NADPH (Correct answer)
Correct answer: ATP and NADPH
The light-dependent reactions capture light energy and use it to produce ATP and NADPH. These energy-rich molecules are then used in the light-independent reactions (Calvin cycle) to fix carbon dioxide and synthesize glucose.
Question 6: Which of the following is a key difference between glycolysis and gluconeogenesis?
- Glycolysis occurs in the cytoplasm, while gluconeogenesis occurs in the mitochondria.
- Glycolysis is an anabolic process, while gluconeogenesis is a catabolic process.
- Glycolysis produces ATP, while gluconeogenesis consumes ATP. (Correct answer)
- Both pathways use the exact same enzymes but in reverse directions.
Correct answer: Glycolysis produces ATP, while gluconeogenesis consumes ATP.
Glycolysis is a catabolic pathway that breaks down glucose, resulting in a net production of ATP. Gluconeogenesis is an anabolic pathway that synthesizes glucose, requiring the input of energy in the form of ATP and GTP. While many steps are reversible, key irreversible steps in glycolysis are bypassed by different enzymes in gluconeogenesis. Both pathways occur primarily in the cytoplasm, with some reactions of gluconeogenesis starting in the mitochondria.
DAT - Dental Admission Biology: Cellular Metabolism Questions and Answers 1
A scientist is studying a facultative anaerobe.
Under which condition would the organism produce the most ATP per molecule of glucose?