Biochemistry: Metabolism and Enzymes
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Questions and Answers

What is the correct definition of anabolism?

  • The process of energy release during cellular respiration
  • Transport of nutrients across cell membranes
  • Synthesis of larger molecules from smaller ones (correct)
  • Degradation of larger molecules into smaller ones

    • Which statement accurately describes enzyme activity?

  • Enzymes can lower the activation energy required for a reaction. (correct)
  • Enzymes are permanently changed after the reactions.
  • Enzymes become integrated into the reaction products.
  • Enzymes are only effective at high temperature ranges.

    • Which of the following best describes the role of ATP in cells?

  • ATP is mainly involved in storing genetic information.
  • ATP acts as a structural component of cell membranes.
  • ATP serves as the energy currency of the cell. (correct)
  • ATP is primarily used for synthesizing proteins.

    • What is the primary effect of temperature on enzyme activity?

    <p>Enzymes function optimally at a specific temperature range.</p> Signup and view all the answers

    In biological oxidation-reduction reactions, what occurs during oxidation?

    <p>A substance loses electrons.</p> Signup and view all the answers

    How do enzymes interact with their substrates?

    <p>Enzymes bind substrates at an active site to facilitate reactions.</p> Signup and view all the answers

    Which source of energy is associated with molecular motion?

    <p>Thermal (heat) energy</p> Signup and view all the answers

    Which of the following statements is NOT true about enzymes?

    <p>Enzymes permanently change their structure after reactions.</p> Signup and view all the answers

    What is the primary purpose of glycolysis in cellular respiration?

    <p>To produce ATP and pyruvate</p> Signup and view all the answers

    Where does the Krebs cycle occur within the cell?

    <p>Mitochondrial matrix</p> Signup and view all the answers

    After glycolysis, what is the next molecule produced that enters the Krebs cycle?

    <p>Acetyl-CoA</p> Signup and view all the answers

    How many ATP molecules are produced during the Krebs cycle for each molecule of acetyl-CoA that enters?

    <p>2</p> Signup and view all the answers

    What is the main function of the electron transport chain in aerobic respiration?

    <p>To harness energy from electrons to produce ATP</p> Signup and view all the answers

    What is produced during lactic acid fermentation?

    <p>Lactate</p> Signup and view all the answers

    What is the net gain of ATP from glycolysis?

    <p>2</p> Signup and view all the answers

    Which molecule can serve as an alternative electron acceptor during anaerobic respiration?

    <p>Nitrate</p> Signup and view all the answers

    What is a key difference between aerobic and anaerobic respiration in terms of ATP production?

    <p>Aerobic respiration produces significantly more ATP</p> Signup and view all the answers

    What is the final electron acceptor in aerobic respiration?

    <p>O₂</p> Signup and view all the answers

    During alcoholic fermentation, what are the end products?

    <p>Ethanol and CO₂</p> Signup and view all the answers

    What is generated as a waste product during the Krebs cycle?

    <p>CO₂</p> Signup and view all the answers

    In which phase of glycolysis is glucose phosphorylated to form fructose-1,6-bisphosphate?

    <p>Energy Investment Phase</p> Signup and view all the answers

    Why is fermentation important for cells in anaerobic conditions?

    <p>It allows glycolysis to continue by regenerating NAD⁺</p> Signup and view all the answers

    What defines the process of catabolism in metabolism?

    <p>Larger molecules are broken down into smaller ones, releasing energy.</p> Signup and view all the answers

    What role do cofactors play in enzyme function?

    <p>They can include metal ions or organic molecules that assist enzymatic reactions.</p> Signup and view all the answers

    How do enzymes achieve lower activation energy in chemical reactions?

    <p>By positioning substrates in a way that promotes interaction.</p> Signup and view all the answers

    What is a characteristic feature of ATP that allows it to serve as the energy currency of the cell?

    <p>Energy is stored in the bond between its second and third phosphate groups.</p> Signup and view all the answers

    Which of the following best describes the relationship between oxidation and reduction reactions?

    <p>Oxidation involves losing electrons, while reduction involves gaining electrons.</p> Signup and view all the answers

    Which of the following statements accurately describes the characteristics of enzymes?

    <p>Enzymes lower activation energy and can be reused after reactions.</p> Signup and view all the answers

    Which form of energy is directly associated with the movement of electrons?

    <p>Electrical energy</p> Signup and view all the answers

    What is one of the primary functions of enzymes in biological systems?

    <p>To act as catalysts for biochemical reactions.</p> Signup and view all the answers

    What is the primary purpose of the Krebs cycle during cellular respiration?

    <p>To generate high-energy electron carriers</p> Signup and view all the answers

    During glycolysis, which molecule is broken down into pyruvate?

    <p>Glucose</p> Signup and view all the answers

    What are the end products of lactic acid fermentation?

    <p>Lactate and NAD⁺</p> Signup and view all the answers

    Which step in the Krebs cycle produces ATP or GTP?

    <p>Substrate-level phosphorylation</p> Signup and view all the answers

    What occurs in the mitochondrial matrix during cellular respiration?

    <p>Krebs cycle and pyruvate decarboxylation</p> Signup and view all the answers

    What role do NADH and FADH₂ play in the electron transport chain?

    <p>They donate electrons to drive ATP synthesis</p> Signup and view all the answers

    In anaerobic respiration, what is the primary purpose of fermentation?

    <p>To regenerate NAD⁺ for continued glycolysis</p> Signup and view all the answers

    How many molecules of ATP are typically produced from one molecule of glucose through aerobic respiration?

    <p>36–38</p> Signup and view all the answers

    What substance is produced as a waste product during the Krebs cycle?

    <p>CO₂</p> Signup and view all the answers

    What is the function of acetyl-CoA in cellular respiration?

    <p>To initiate the Krebs cycle</p> Signup and view all the answers

    How does alcoholic fermentation contribute to biotechnology?

    <p>It is crucial for brewing and winemaking processes</p> Signup and view all the answers

    In which phase of the Krebs cycle is citric acid formed?

    <p>Entering phase with acetyl-CoA</p> Signup and view all the answers

    What is the link between the electron transport chain and oxidative phosphorylation?

    <p>The ETC generates a proton gradient for ATP synthesis</p> Signup and view all the answers

    Study Notes

    Metabolism

    • Metabolism encompasses all the chemical reactions within a cell.
    • Two types:
      • Anabolism (Biosynthesis): Builds larger molecules from smaller ones, forming cell structures.
      • Catabolism: Degrades larger molecules into smaller ones, usually releasing energy.

    Enzymes

    • Enzymes are protein catalysts that accelerate metabolic reactions.
    • They are not consumed or changed by the reaction.
    • They have an active site for substrates.
    • They lower the activation energy, the energy required to start a reaction.
    • Enzyme activity is greatly affected by temperature and pH.
    • They require cofactors (non-protein components) for some functions.

    Energy Sources and Transfer

    • Cells utilize various energy forms: thermal (heat), radiant, electrical, mechanical, atomic, and chemical (energy stored in molecular bonds).
    • Oxidation-reduction reactions (redox) are crucial for energy transfer.
      • Oxidation: Loss of electrons.
      • Reduction: Gain of electrons.
      • Redox reactions always occur together.

    ATP

    • ATP (adenosine triphosphate) is the cell's primary energy currency, providing readily available energy from the bond between the second and third phosphate groups.
      • It consists of adenine, ribose, and three phosphate groups.

    Aerobic Respiration

    • Aerobic respiration, in the presence of oxygen, is the main pathway for ATP production.
    • It includes four key stages:
      • Glycolysis: Breaks down glucose into pyruvate in the cytoplasm.
      • Pyruvate Decarboxylation: Converts pyruvate to Acetyl-CoA in the mitochondrial matrix.
      • Krebs Cycle: Oxidizes Acetyl-CoA, releasing CO₂ and generating electron carriers (NADH, FADH₂).
      • Electron Transport Chain/Oxidative Phosphorylation: Electrons from NADH & FADH₂ power ATP production through ATP synthase.

    Glycolysis

    • Input: 1 glucose, 2 ATP, 2 NAD⁺.
    • Output: 2 pyruvate, 4 ATP (net gain 2 ATP), 2 NADH.
    • Steps: Energy investment, cleavage, energy payoff stages.
    • Crucial for linking to Krebs cycle and oxidative phosphorylation.

    Krebs Cycle

    • Cycle happens in the mitochondrial matrix.
    • Input: 2 Acetyl-CoA, 6 NAD⁺, 2 FAD, 2 ADP (or GDP).
    • Output: 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP (or GTP).
    • Regenerates oxaloacetate; links to oxidative phosphorylation by providing electron carriers.

    Aerobic Respiration Summary

    • Input: 1 glucose, oxygen.
    • Output: CO₂, H₂O, ~36-38 ATP.

    Anaerobic Respiration

    • Occurs without oxygen.
    • Different final electron acceptors (e.g., nitrate, sulfate) than oxygen are used.
    • Yields less ATP than aerobic respiration.
    • Sometimes follows glycolysis by fermentation reactions to regenerate NAD⁺.

    Fermentation

    • Fermentation regenerates NAD⁺, allowing glycolysis to continue in the absence of oxygen.
    • Different types:
      • Lactic acid fermentation: Produces lactate from pyruvate.
      • Alcoholic fermentation: Produces ethanol from pyruvate.

    Photosynthesis

    • Converts light energy to chemical energy in glucose.

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    Description

    This quiz covers essential concepts in biochemistry, focusing on metabolism and enzymatic functions. It examines both anabolic and catabolic pathways, as well as the role of enzymes as catalysts in cellular reactions. Test your understanding of energy sources and transfer mechanisms.

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