Which cellular process primarily occurs in mitochondria in eukaryotic cells?

• A. Glycolysis in the cytosol
• B. DNA replication of the nuclear genome
• C. Protein synthesis on cytosolic ribosomes free in the cytoplasm
• D. Oxidative phosphorylation (electron transport chain and ATP synthesis)

Answer: (D)

Verified step by step guidance

1. Identify the main functions of mitochondria in eukaryotic cells, focusing on energy production processes.
2. Recall that glycolysis occurs in the cytosol, not in mitochondria, so it is not the primary mitochondrial process.
3. Understand that DNA replication of the nuclear genome happens in the nucleus, not in mitochondria.
4. Recognize that protein synthesis on free cytosolic ribosomes occurs in the cytoplasm, separate from mitochondria.
5. Conclude that oxidative phosphorylation, which includes the electron transport chain and ATP synthesis, is the primary cellular process that takes place in mitochondria.