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Cellular Respiration and Fermentation - General Biology

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  • What is the overall chemical equation for cellular respiration?

    Glucose (\(C_6H_{12}O_6\)) reacts with oxygen (\(O_2\)) to produce carbon dioxide (\(CO_2\)), water (\(H_2O\)), and energy (ATP).

  • Define oxidation and reduction in redox reactions.

    Oxidation is the loss of electrons; reduction is the gain of electrons. These reactions transfer energy in cells.

  • What role does NAD+ play in cellular respiration?

    NAD+ is an electron acceptor that becomes reduced to NADH, storing high-energy electrons for later use in the electron transport chain.

  • What are the three main stages of cellular respiration?

    1. Glycolysis (cytosol)
    2. Citric Acid Cycle (mitochondrial matrix)
    3. Oxidative Phosphorylation (inner mitochondrial membrane)

  • What is the net yield of ATP, NADH, and pyruvate from glycolysis per glucose molecule?

    2 ATP (net), 2 NADH, and 2 pyruvate molecules are produced per glucose molecule.

  • What is substrate-level phosphorylation?

    ATP formation directly by transferring a phosphate group from a substrate to ADP during glycolysis and the citric acid cycle.

  • How is pyruvate converted before entering the citric acid cycle?

    Pyruvate is oxidized and combined with Coenzyme A to form Acetyl-CoA, releasing CO2 and producing NADH.

  • What is the main function of the citric acid cycle?

    To oxidize Acetyl-CoA to CO2 and generate NADH, FADH2, and GTP (ATP equivalent) for energy extraction.

  • What is the electron transport chain (ETC)?

    A series of protein complexes in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient.

  • What is the proton motive force (PMF)?

    The electrochemical gradient of protons across the inner mitochondrial membrane that drives ATP synthesis.

  • How does ATP synthase produce ATP?

    Protons flow back into the mitochondrial matrix through ATP synthase, which uses this energy to phosphorylate ADP to ATP.

  • What is oxidative phosphorylation?

    The process of ATP production using energy derived from the electron transport chain and chemiosmosis.

  • Compare aerobic and anaerobic respiration.

    Aerobic respiration uses oxygen as the final electron acceptor; anaerobic respiration uses other molecules, producing less ATP.

  • What is fermentation and why is it important?

    Fermentation regenerates NAD+ by oxidizing NADH when oxygen is absent, allowing glycolysis to continue producing ATP.

  • Describe lactic acid fermentation.

    Pyruvate is reduced by NADH to form lactate, regenerating NAD+ without releasing CO2; occurs in muscle cells and some microbes.

  • Describe alcohol fermentation.

    Pyruvate is converted to ethanol and CO2, regenerating NAD+; used by yeast in brewing and baking.

  • Why must glycolysis be coupled with fermentation or cellular respiration?

    To regenerate NAD+ from NADH, ensuring glycolysis can continue producing ATP under aerobic or anaerobic conditions.

  • What is the role of Coenzyme A (CoA) in metabolism?

    CoA activates Acetyl groups, forming Acetyl-CoA, which enters the citric acid cycle for energy extraction.

  • What are the main products of one turn of the citric acid cycle?

    3 NADH, 1 FADH2, 1 GTP (ATP), and 2 CO2 molecules per Acetyl-CoA oxidized.

  • How many ATP molecules are produced per glucose molecule by cellular respiration?

    About 30 to 32 ATP molecules are produced per glucose molecule through glycolysis, citric acid cycle, and oxidative phosphorylation.