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Unit 3: Energy, Enzymes, and Cellular Respiration

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이 집합의 용어 (24)

  • Why do all living systems require a constant input of energy?
    Energy is needed for growth, reproduction, transport, movement, repair, and maintaining homeostasis. Without energy flow, cells lose function and the organism dies.
  • What does the second law of thermodynamics state and how does life comply?
    Every energy transfer increases entropy (disorder). Life maintains internal order by taking in energy and releasing heat, increasing the entropy of surroundings.
  • Difference between endergonic and exergonic reactions
    Endergonic reactions require energy input (ΔG>0), products have more free energy. Exergonic reactions release energy (ΔG<0), products have less free energy.
  • How do cells couple energy-releasing and energy-requiring reactions?
    Cells couple exergonic reactions to endergonic ones so the overall process releases free energy, e.g., ATP hydrolysis powers active transport and synthesis.
  • Role of ATP in energy coupling
    ATP hydrolysis releases free energy by converting ATP to ADP and Pi. ATP transfers its terminal phosphate to molecules, making them more reactive.
  • Why are metabolic pathways sequential?
    Sequential enzyme-controlled steps allow regulation, energy capture in manageable amounts, and prevent energy waste.
  • Why are metabolic pathways conserved across life domains?
    Pathways like glycolysis evolved early and are present in bacteria, archaea, and eukaryotes, indicating common ancestry and efficiency.
  • What are enzymes made of and what is an active site?
    Most enzymes are proteins made of amino acids; some are RNA (ribozymes). The active site is where the substrate binds and the reaction occurs.
  • What is induced fit in enzyme-substrate interaction?
    The active site changes shape slightly to better fit the substrate, stabilizing the transition state and positioning reactants.
  • What is activation energy and how do enzymes affect it?
    Activation energy is the energy needed to start a reaction. Enzymes lower it by providing an alternative pathway and stabilizing the transition state.
  • How do temperature and pH extremes affect enzymes?
    Extreme temperature or pH can denature enzymes by disrupting bonds, altering the active site and preventing substrate binding.
  • How does increasing temperature affect enzyme activity?
    Reaction rates increase with temperature until the enzyme denatures above its optimal temperature, causing a sharp rate decrease.
  • Effect of substrate and product concentration on enzyme activity
    Increasing substrate increases rate until saturation (Vmax). Product accumulation can inhibit the reaction or reverse it.
  • Difference between competitive and noncompetitive enzyme inhibitors
    Competitive inhibitors bind active site and can be outcompeted by substrate; noncompetitive bind elsewhere and alter enzyme function, not overcome by substrate.
  • Purpose of fermentation and cellular respiration
    Both produce usable energy from organic molecules. Respiration uses oxygen to produce ~30-32 ATP; fermentation regenerates NAD⁺ for glycolysis, yielding 2 ATP.
  • What are redox reactions in cellular respiration?
    Redox involves electron transfer: oxidation (loss of electrons) and reduction (gain). Glucose is oxidized; oxygen is reduced to water.
  • What happens to glucose during glycolysis?
    Glucose (6C) is split into two pyruvate (3C) molecules in the cytosol, producing a net 2 ATP and 2 NADH without requiring oxygen.
  • Chemical products of glycolysis and energy distribution
    Produces 2 pyruvate, 2 NADH, net 2 ATP, and 2 water molecules. Energy is stored in ATP, NADH, and pyruvate.
  • Fate of pyruvate after glycolysis
    With oxygen, pyruvate enters mitochondria, converts to acetyl-CoA, releasing CO₂ and producing NADH. Without oxygen, it undergoes fermentation.
  • Products of the citric acid (Krebs) cycle per glucose
    4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP (or GTP). The cycle completes acetyl group oxidation in mitochondria.
  • Role of NADH and FADH₂ in respiration
    They are reduced electron carriers transporting high-energy electrons to the electron transport chain for ATP production.
  • Function of the mitochondrial electron transport chain (ETC)
    ETC transfers electrons through complexes, pumping H⁺ into intermembrane space, creating a proton gradient used by ATP synthase to make ATP.
  • Where is the proton gradient created in mitochondria?
    Across the inner mitochondrial membrane: high H⁺ in intermembrane space, low H⁺ in matrix; protons return via ATP synthase.
  • Role of the proton gradient in ATP synthesis
    The proton-motive force drives H⁺ flow through ATP synthase, which uses this energy to combine ADP and Pi into ATP.