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Cellular Respiration and Energy Metabolism

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Termini in questo insieme (20)

  • What is the overall purpose of cellular respiration?
    To transfer energy from food molecules into ATP, the cell's usable energy currency.
  • What are the three main stages of cellular respiration?
    1. Glycolysis, 2. Pyruvate oxidation and the Citric Acid Cycle, 3. Oxidative phosphorylation.
  • Where does glycolysis occur and what does it produce?
    Occurs in the cytosol; breaks glucose into two pyruvate molecules and produces a net of 2 ATP and 2 NADH.
  • What happens during pyruvate oxidation?
    Pyruvate is converted into acetyl CoA, releasing CO₂ and producing NADH; occurs in the mitochondrial matrix in eukaryotes.
  • What is the Citric Acid Cycle's role in cellular respiration?
    It oxidizes acetyl CoA to CO₂, producing NADH, FADH₂, and ATP through substrate-level phosphorylation.
  • What is oxidative phosphorylation?
    The process where electrons from NADH and FADH₂ pass through the electron transport chain to generate a proton gradient that drives ATP synthesis.
  • What are redox reactions in cellular respiration?
    Reactions involving electron transfer; oxidation is loss of electrons, reduction is gain of electrons.
  • What are the main electron carriers in cellular respiration?
    NAD⁺ and FAD, which become reduced to NADH and FADH₂ by accepting electrons.
  • Why is energy released stepwise in cellular respiration?
    To prevent energy loss as heat and to harvest energy efficiently by passing electrons through carriers gradually.
  • Describe substrate-level phosphorylation.
    An enzyme directly transfers a phosphate group from a substrate to ADP to form ATP; occurs in glycolysis and the citric acid cycle.
  • Describe oxidative phosphorylation.
    ATP is produced using energy from electrons carried by NADH and FADH₂ via the electron transport chain and chemiosmosis.
  • What is the role of mitochondria in cellular respiration?
    Mitochondria house the citric acid cycle and oxidative phosphorylation; their inner membrane contains the electron transport chain and ATP synthase.
  • What is the proton-motive force?
    The electrochemical gradient of H⁺ ions across the inner mitochondrial membrane that drives ATP synthesis.
  • How does ATP synthase produce ATP?
    H⁺ ions flow back into the mitochondrial matrix through ATP synthase, which uses this energy to phosphorylate ADP to ATP.
  • What is the net ATP yield from complete oxidation of one glucose molecule?
    Approximately 30–32 ATP molecules per glucose in eukaryotic cells.
  • What happens to cellular respiration in the absence of oxygen?
    Aerobic electron transport stops; cells use anaerobic respiration or fermentation to produce ATP.
  • What is fermentation?
    A process combining glycolysis and reactions that regenerate NAD⁺ without an electron transport chain, producing ATP by substrate-level phosphorylation.
  • Describe alcohol fermentation.
    Pyruvate is converted to ethanol and CO₂; NADH is oxidized back to NAD⁺ to allow glycolysis to continue.
  • Describe lactic acid fermentation.
    Pyruvate is directly reduced by NADH to form lactate; NADH is oxidized back to NAD⁺ without releasing CO₂.
  • Compare ATP production in fermentation, anaerobic, and aerobic respiration.
    Fermentation produces the least ATP via substrate-level phosphorylation; anaerobic and aerobic respiration use oxidative phosphorylation, with aerobic usually producing the most ATP.