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Biochemical Energy Generation and Metabolism

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  • What are the principal food molecules broken down for energy?
    Lipids, proteins, and carbohydrates are broken down into simple sugars, fatty acids, glycerol, and amino acids before cellular energy production.
  • What are the main types of cellular work requiring energy?
    Biosynthesis, active transport, and motility are key energy-requiring processes in cells.
  • What is the overall chemical equation for energy release from food molecules?
    Food molecules (C, H, O) + O2 → CO2 + H2O + Energy.
  • What is bioenergetics?
    The quantitative study of energy transductions and chemical processes underlying energy conversions in living cells.
  • What does a negative ΔG indicate in a biochemical reaction?
    A negative ΔG means the reaction is exergonic and spontaneous, releasing free energy.
  • Difference between exergonic and exothermic reactions?
    Exergonic refers to free energy release (negative ΔG), while exothermic refers to heat release (negative ΔH).
  • What is the role of mitochondria in energy production?
    Mitochondria produce about 90% of cellular ATP via the citric acid cycle and electron transport chain.
  • What is acetyl coenzyme A (acetyl-SCoA)?
    An intermediate carrying two-carbon acetyl groups into the citric acid cycle for oxidation.
  • What are the four stages of catabolism?
    1) Digestion, 2) Acetyl-SCoA production, 3) Citric acid cycle, 4) ATP production via electron transport.
  • What is substrate-level phosphorylation?
    Formation of ATP by direct transfer of a phosphate group from a phosphorylated substrate to ADP.
  • What is oxidative phosphorylation?
    ATP synthesis coupled to electron transport and redox reactions in mitochondria.
  • Why is ATP called a high-energy molecule?
    Because hydrolysis of its phosphoanhydride bonds releases a useful amount of energy for cellular work.
  • What is the function of NAD+ and FAD in metabolism?
    They act as oxidizing agents, accepting electrons and becoming reduced to NADH and FADH2.
  • What is the net result of the citric acid cycle?
    Oxidation of acetyl-SCoA to CO2, production of 3 NADH, 1 FADH2, and 1 ATP (or GTP) per cycle turn.
  • How is the citric acid cycle regulated?
    By availability of acetyl-SCoA, NAD+, FAD, and allosteric effectors like ADP and NADH.
  • What is the electron-transport chain?
    A series of redox reactions transferring electrons from NADH and FADH2 to oxygen, coupled to ATP synthesis.
  • What is the final electron acceptor in the electron-transport chain?
    Molecular oxygen (O2), which combines with electrons and protons to form water.
  • What is chemiosmotic coupling?
    The process where proton gradients across the mitochondrial membrane drive ATP synthesis via ATP synthase.
  • How many ATP molecules are produced per NADH oxidized?
    Approximately 3 ATP molecules are produced per NADH oxidized in the electron-transport chain.
  • What effect do respiratory inhibitors have?
    They block electron flow at specific sites in the electron-transport chain, halting ATP production.