Question

Even in the absence of mitochondria, the Krebs cycle takes place in a prokaryotic cell. What is the site of this Krebs cycle in the cell?

• A. Mesosomes
• B. Nucleoid
• C. Cytoplasm
• D. Ribosomes

Hint:

Sites of Cellular Respiration:
Eukaryotes: Glycolysis in Cytosol; TCA in Mitochondrial Matrix; ETC in Inner Mitochondrial Membrane.
Prokaryotes: Glycolysis & TCA in Cytoplasm; ETC in Plasma Membrane.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Prokaryotes lack membrane-bound organelles; soluble Krebs cycle enzymes reside in the cytosol, and respiratory electron transport occurs across the plasma membrane.

Step 2: Detailed Explanation:
In aerobic bacteria (prokaryotes):
- Because bacterial cells lack membrane-delimited mitochondria, all the soluble enzymes of the Krebs (TCA) cycle (such as citrate synthase, aconitase, isocitrate dehydrogenase, $\alpha$-ketoglutarate dehydrogenase, and malate dehydrogenase) operate in the aqueous Cytoplasm (Cytosol).
- (The membrane-bound succinate dehydrogenase Complex II and the electron transport chain components are embedded in the bacterial plasma membrane).

Step 3: Final Answer:
Therefore, the site of the Krebs cycle in prokaryotes is the Cytoplasm, corresponding to option (C).