Question

All enzymes of $TCA$ cycle are located in the mitochondrial matrix except one which is located in inner mitochondrial membranes in eukaryotes and in cytosol in prokaryotes. This enzyme is

• A. Malate dehydrogenase
• B. Isociatrate dehydrogenase
• C. Succinate dehydrogenase
• D. Lactate dehydrogenase

Answer 1

The Correct Option is C

The given question is asking about the location of enzymes involved in the TCA (Tricarboxylic Acid) cycle, also known as the Krebs cycle. Most of these enzymes are located in the mitochondrial matrix in eukaryotic cells. However, there is one notable exception that the question focuses on.

Let's evaluate the options provided:

• Malate dehydrogenase: This enzyme is part of the TCA cycle and catalyzes the conversion of malate to oxaloacetate. It is located in the mitochondrial matrix.
• Isocitrate dehydrogenase: This enzyme catalyzes the oxidative decarboxylation of isocitrate into alpha-ketoglutarate and is also found in the mitochondrial matrix.
• Succinate dehydrogenase: This is the correct answer. Unlike other enzymes in the TCA cycle, succinate dehydrogenase is embedded in the inner mitochondrial membrane in eukaryotes. In prokaryotes, it is associated with the cell membrane and functions in the cytosol. Succinate dehydrogenase is also known as Complex II in the electron transport chain.
• Lactate dehydrogenase: This enzyme is involved in the conversion of pyruvate into lactate and is not part of the TCA cycle. It is present in the cytoplasm.

Therefore, the enzyme that deviates from the typical mitochondrial matrix location of TCA cycle enzymes and is instead located in the inner mitochondrial membranes in eukaryotes is Succinate dehydrogenase.

Conclusion: The correct answer to the question is Succinate dehydrogenase, as it is uniquely positioned in the inner mitochondrial membrane and integrates the TCA cycle with the electron transport chain.