Question

Match the enzymes in Column I with the cellular compartments in Column II.

Which of the following combinations is correct?

• A. P - (ii); Q - (iii); R - (i); S - (iv)
• B. P - (iv); Q - (i); R - (iii); S - (ii)
• C. P - (iii); Q - (ii); R - (i); S - (v)
• D. P - (iii); Q - (i); R - (iv); S - (ii)

Hint:

Succinate dehydrogenase is an excellent marker enzyme for the inner mitochondrial membrane.
Remembering this single fact instantly points to P - (ii), allowing you to find the correct answer (A) immediately!

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
We need to match the key cellular enzymes involved in respiration and energy production (Column I) with their specific subcellular locations (Column II).

Step 2: Key Formula or Approach:
Let's recall the locations of metabolic pathways:
1. Glycolysis and Fermentation: Occurs in the cytoplasm. Thus, Lactate dehydrogenase (catalyzing pyruvate $\leftrightarrow$ lactate) is cytoplasmic.
2. Link Reaction: Occurs in the mitochondrial matrix. Thus, Pyruvate dehydrogenase is located here.
3. Krebs Cycle: Mostly occurs in the mitochondrial matrix, except for Succinate dehydrogenase, which is membrane-bound.
4. Oxidative Phosphorylation and Photophosphorylation: ATP Synthase complexes are located on the inner mitochondrial membrane and the thylakoid membrane of chloroplasts.

Step 3: Detailed Explanation:
Let's do the matching:
- P. Succinate dehydrogenase: This is a unique Krebs cycle enzyme because it is bound to the inner mitochondrial membrane (acting as Complex II of the respiratory chain). Thus, P matches (ii).
- Q. Pyruvate dehydrogenase: This multi-enzyme complex catalyzes the decarboxylation of pyruvate to acetyl-CoA inside the mitochondrial matrix. Thus, Q matches (iii).
- R. Lactate dehydrogenase: This enzyme catalyzes the reversible conversion of pyruvate to lactate during anaerobic respiration in the cytoplasm. Thus, R matches (i).
- S. ATP synthase: This complex is responsible for ATP synthesis during light reactions of photosynthesis and is located on the thylakoid membrane of chloroplasts (or inner mitochondrial membrane). Among the choices, matching S with (iv) (thylakoid membrane) yields the correct and complete set.
Let's check the combinations:
- P - (ii), Q - (iii), R - (i), S - (iv) corresponds to option (A).

Step 4: Final Answer:
The only correct matching combination is option (A).