Question

Enzymes of TCA cycle are located in the mitochondrial matrix except one which is located in the inner mitochondrial membrane in eukaryotes and in cytosol in prokaryotes. This enzyme is
A. Succinate dehydrogenase
B. Lactate dehydrogenase
C. Isocitrate dehydrogenase
D. Malate dehydrogenase

Answer 1

Hint: This enzyme activates the oxidation of succinate to fumarate in the Krebs cycle, obtained electrons being utilized to the respiratory chain complex III to decrease oxygen and produce water. It is the only one enzyme that is involved in both the electron transport chain and the citric acid cycle.

Complete answer:
- TCA cycle is an arrangement of enzyme-activation chemical reactions that is the main vital in all living cells that utilize oxygen as a portion of cellular respiration. In eukaryotic cells, the citric acid cycle happens in the matrix of the mitochondrion.
- Enzymes involved in TCA pathway are- citrate synthase, aconitase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinyl coenzyme A synthetase, succinate dehydrogenase, fumarase, malate dehydrogenase.
- All the oxidative enzymes found in the TCA are present in the matrix excluding the enzyme succinic dehydrogenase. This enzyme activates the altering of succinic acid into fumaric acid. - The enzyme is an integral protein complex that is closely bounced to the interior mitochondrial membrane. And also, this enzyme is the favored marker enzyme for interior membranes whilst performing mitochondrial fractionations. In prokaryotes, it is present in the cytosol.
- Lactate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase all these enzymes are located in the mitochondrial matrix of cell as mentioned above.

Thus, the correct option is A. i.e. Succinate dehydrogenase.

Note: Succinate dehydrogenase is an enzyme complex, found in many bacterial cells and in the inner mitochondrial membrane of eukaryotes. It is the only enzyme that participates in both the citric acid cycle and the electron transport chain. Histochemical studies displaying rich succinate dehydrogenase in muscle demonstrates rich mitochondrial content and rich oxidative possibilities.