The most primitive respiratory process occurring in a living cell is:
Correct answer: C. Glycolysis
- A. Lactic acid fermentation
- B. Alcoholic fermentation
- C. Glycolysis
- D. Krebs's cycle
Explanation
Glycolysis occurs in the cytoplasm of every living cell, needs no oxygen and no organelle, and is common to bacteria, plants and animals alike, which marks it as the oldest of these pathways, dating from before the atmosphere contained oxygen. The two fermentations are add ons that merely regenerate NAD so glycolysis can continue. The Krebs cycle is later still, since it requires a mitochondrion and oxygen further down the chain.
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About Cellular Respiration
Cellular respiration releases energy from glucose through glycolysis, the link reaction, the Krebs cycle and the electron transport chain, producing ATP. The pathway differs in oxygen availability: aerobic respiration uses oxygen and yields more ATP, while anaerobic respiration produces much less ATP and forms lactic acid in muscles or ethanol and carbon dioxide in yeast.
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