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🔬 Biology  ·  Respiration in Plants  ·  NEET

The first stage of respiration, in which glucose is split into pyruvate, is:

Answer: glycolysis.

  • A glycolysis
  • B the Krebs cycle
  • C electron transport
  • D the Calvin cycle

Correct answer: A. glycolysis

Explanation: Glycolysis splits one glucose into two molecules of pyruvate.

Aerobic Respiration: Three StagesGlycolysiscytoplasmnet 2 ATP, 2 NADHKrebs Cyclemitochondrial matrixper glucose: 6 NADH, 2 FADH2, 2 ATPElectron Transport Chaininner mitochondrial membrane~32-34 ATP (bulk of total)Total: ~36-38 ATP per glucose - the ETC alone supplies most of itO2 is required only at the LAST step (ETC), as the final electron acceptor

Aerobic respiration unfolds in three locations: glycolysis in the cytoplasm yields a small amount of ATP directly, the Krebs cycle in the mitochondrial matrix harvests electron carriers (NADH, FADH2), and the electron transport chain in the inner mitochondrial membrane uses those carriers to generate the bulk of the ATP, with O2 needed only at this final stage.

Concept context

Glycolysis, the Krebs cycle, the electron transport chain, fermentation, and the respiratory quotient. The cellular energy-release counterpart to photosynthesis.

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