Question

In which of the following organelles are the enzyme pyruvate dehydrogenase complex and the glycolytic pathway located?

• A. Cytosol and Mitochondria
• B. Cytosol and chloroplast
• C. Golgi bodies and ER
• D. Microsomes and ribosomes

Hint:

Glycolysis needs no organelle, while the pyruvate dehydrogenase step needs the mitochondrial matrix.

Answer 1

The Correct Option is A

This question checks if you know exactly where, inside the cell, two connected steps of respiration take place, glycolysis and the pyruvate dehydrogenase reaction that follows it.

1. Cytosol and Mitochondria: glycolysis breaks glucose down to pyruvate in the cytosol without needing any organelle, and then the pyruvate dehydrogenase complex, sitting inside the mitochondrial matrix, converts that pyruvate to acetyl-CoA. Both processes match this pair of locations exactly.
2. Cytosol and chloroplast: the cytosol part is right for glycolysis, but chloroplasts run photosynthesis, not the pyruvate dehydrogenase reaction, so this pairing is wrong.
3. Golgi bodies and ER: these handle protein modification, packaging and lipid synthesis, they play no part in glycolysis or pyruvate oxidation.
4. Microsomes and ribosomes: microsomes are lab-prepared membrane fragments and ribosomes make proteins, neither is where glycolysis or the pyruvate dehydrogenase complex functions.

Only the first option correctly places glycolysis in the cytosol and the pyruvate dehydrogenase complex in the mitochondria.

Let's summarize:

• Glycolysis happens in the cytosol and needs no oxygen or organelle.
• The pyruvate dehydrogenase complex works in the mitochondrial matrix, the link step before the Krebs cycle.

So the correct answer is Cytosol and Mitochondria.