Biochemistry: Metabolic Reactions Quiz
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Questions and Answers

Which type of reaction involves the synthesis of large molecules from smaller ones?

  • Endergonic reactions
  • Anabolic reactions (correct)
  • Exergonic reactions
  • Catabolic reactions

    • In which type of metabolic reaction is energy released?

  • Glycogenolysis
  • Anabolic reactions
  • Photosynthesis
  • Catabolic reactions (correct)

    • What is the primary role of coenzymes like NAD+ in metabolic processes?

  • Synthesize carbohydrates
  • Store energy in ATP
  • Facilitate oxidative reactions (correct)
  • Catalyze phosphorylation

    • Which of the following reactions is an example of an anabolic reaction?

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

    What is the standard Gibbs free energy change sign for catabolic reactions?

    <p>Negative (-∆G)</p> Signup and view all the answers

    What is produced when pyruvate is converted through oxidative decarboxylation?

    <p>Acetyl CoA, CO2, NADH, and H+</p> Signup and view all the answers

    What role does the TCA cycle primarily play in the body?

    <p>It generates most of the energy needed for the brain</p> Signup and view all the answers

    What effect does a deficiency in pyruvate dehydrogenase have on the body?

    <p>Lactic acidosis due to impaired acetyl CoA formation</p> Signup and view all the answers

    How many ATP molecules are generated from one molecule of acetyl CoA during the TCA cycle?

    <p>10 ATP</p> Signup and view all the answers

    Where does oxidative decarboxylation of pyruvate occur in the cell?

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

    Which shuttle mechanism produces 1.5 ATP molecules per cytoplasmic NADH?

    <p>Glycerol phosphate shuttle</p> Signup and view all the answers

    What is the net result of the oxidation of one molecule of glucose in terms of ATP and CO2 produced?

    <p>2 ATP and 4 CO2</p> Signup and view all the answers

    Which complex in the electron transport chain is directly after NADH dehydrogenase?

    <p>Coenzyme Q (ubiquinone)</p> Signup and view all the answers

    In which part of the mitochondria do the reactions of the electron transport chain occur?

    <p>Inner mitochondrial membrane</p> Signup and view all the answers

    How many ATP molecules result from the oxidation of one mitochondrial NADH?

    <p>2.5 ATP</p> Signup and view all the answers

    What does a negative change in free energy (∆G) indicate about a chemical reaction?

    <p>The reaction proceeds spontaneously.</p> Signup and view all the answers

    What is enthalpy (∆H) a measure of in a chemical reaction?

    <p>The heat content change of reactants and products.</p> Signup and view all the answers

    How does the standard free energy change (∆G°) relate to additive reactions?

    <p>The sum of ∆G° values is additive for consecutive reactions.</p> Signup and view all the answers

    What happens when the sum of the ∆G values of individual reactions in a pathway is negative?

    <p>The pathway can proceed as written.</p> Signup and view all the answers

    What does a positive change in free energy (∆G) signify?

    <p>The reaction requires energy input to proceed.</p> Signup and view all the answers

    What is the approximate ∆G° for each of the two terminal phosphate groups of ATP?

    <p>-7.3 kcal/mol</p> Signup and view all the answers

    Which of the following statements regarding the hydrolysis of ATP is correct?

    <p>ATP hydrolysis produces energy.</p> Signup and view all the answers

    What is the relationship between entropy (∆S) and the disorder of reactants and products?

    <p>Entropy is a measure of disorder in the system.</p> Signup and view all the answers

    What is the primary function of carbohydrates in cells?

    <p>To provide energy through oxidation</p> Signup and view all the answers

    Which sugars can be converted to glucose in the liver?

    <p>Fructose and galactose</p> Signup and view all the answers

    What is the net gain of ATP from one molecule of glucose during glycolysis?

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

    If oxygen is absent, pyruvate is converted into which of the following during anaerobic respiration?

    <p>Alcohol or lactate</p> Signup and view all the answers

    Where does glycolysis occur within the cell?

    <p>In the cytoplasm</p> Signup and view all the answers

    What happens to pyruvate if oxygen is present during cellular respiration?

    <p>It is oxidized to carbon dioxide and water</p> Signup and view all the answers

    Which of the following statements is true regarding lactose intolerance?

    <p>Most adults of African and Asian descent are lactase deficient</p> Signup and view all the answers

    Which molecule serves as the central pathway for glucose catabolism?

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

    What is produced at the end of the oxidative phosphorylation process?

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

    Which enzyme catalyzes the conversion of pyruvate to lactate in animals?

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

    What is the primary effect of insulin on glycogen metabolism?

    <p>Induces glycogen synthesis</p> Signup and view all the answers

    What deficiency is responsible for McArdle syndrome?

    <p>Glycogen phosphorylase deficiency</p> Signup and view all the answers

    Which pathway is characterized by the formation of NADPH and 5-C sugars?

    <p>Pentose Phosphate Pathway</p> Signup and view all the answers

    What condition is associated with Von Gierke disease?

    <p>Severe fasting hypoglycaemia</p> Signup and view all the answers

    During prolonged fasting, which organ becomes the major glucose-producing organ?

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

    Which of the following substrates is NOT a precursor for gluconeogenesis?

    <p>Carbon dioxide</p> Signup and view all the answers

    What is the primary function of NADPH produced in oxidative reactions?

    <p>Fatty acid synthesis</p> Signup and view all the answers

    Which hormone is primarily responsible for stimulating glycogen breakdown in the liver?

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

    What is the main consequence of G6PD deficiency?

    <p>Haemolytic anaemia</p> Signup and view all the answers

    Which of the following pathways occurs in the cytosol of the cell?

    <p>Pentose phosphate pathway</p> Signup and view all the answers

    What is the function of glucagon during low blood glucose levels?

    <p>Stimulates glycogen breakdown</p> Signup and view all the answers

    Study Notes

    Carbohydrate Metabolism

    • Carbohydrates are metabolized to create a variety of organic compounds.
    • Animals consume significant amounts of carbohydrates, which can either be stored, oxidized for energy, converted to lipids for more effective energy storage, or used for creating cellular components.
    • A major role for carbohydrates is to be oxidized and provide energy for metabolic processes.
    • Cells primarily utilize glucose as a source of carbohydrates.
    • Fructose and galactose can be readily converted to glucose within the liver.

    Metabolism - Coupling Reactions

    • Some reactions require energy, while others produce it.
    • Coupling reactions are a strategy for initiating energy-requiring reactions by pairing them with energy-releasing reactions.
    • Example of coupling reactions:
      • ATP → ADP -7.3 kcal/mol +3.3 kcal/mol Glucose -> Glu-6-phosphate
      • Phosphoenolpyruvate → Pyruvate -14.8 kcal/mol +7.3 kcal/mol ADP -> ATP

    Metabolism

    • Metabolism is the combination of all the biochemical reactions within an organism.
    • It is integral to building cellular components and utilizing energy from the environment.
    • Metabolism is categorized into two types:
      • Anabolic: Synthesis of complex molecules from simpler ones (requires energy)
      • Catabolic: Breakdown of complex molecules into simpler ones (releases energy)

    Anabolic Reactions

    • Anabolic reactions involve the synthesis of larger molecules from smaller ones.
    • They require an input of energy and are considered endergonic.
    • Example: Photosynthesis, transforming carbon dioxide and water into carbohydrates, with sunlight as the energy source.
    • The creation of complex biological molecules from simpler precursor molecules consumes energy.

    Catabolic Reactions

    • Catabolic reactions are the breakdown of larger molecules into smaller components.
    • Release energy and are called exergonic.
    • Example: Digestion, the breakdown of large food molecules for absorption by the body.
    • These reactions play a role in the breakdown of larger molecules into simpler components, releasing energy as a byproduct.

    Stages of Metabolism

    • Stage 1: Hydrolysis of complex molecules (proteins, polysaccharides, lipids) into their constituent building blocks (amino acids, monosaccharides, glycerol, and fatty acids).
    • Stage 2: Conversion of building blocks to acetyl CoA.
    • Stage 3: Oxidation of acetyl-CoA via the citric acid cycle and oxidative phosphorylation.

    Glycolysis

    • Glycolysis is the central pathway for glucose catabolism, producing energy.
    • Glucose is broken down into 2 pyruvate molecules, 2 ATP, and 2H+ in the cytoplasm.
    • All cells undergo glycolysis to obtain glucose from diet and other catabolic reactions.
    • The fate of pyruvate depends on the presence of oxygen.
      • With oxygen (aerobic): Pyruvate enters the mitochondria for further oxidation, producing carbon dioxide, water and more energy.
      • Without oxygen (anaerobic): Pyruvate converted into alcohol or lactic acid.
    • Input: 1 glucose, 2 ATP, 2 NAD.
    • Output: 2 pyruvate, 4 ATP, 2 NADH, 2 H2O.

    Aerobic Respiration

    • Involves two stages:
      • Oxidative decarboxylation of pyruvate: Removal of CO2 and oxidation.
      • TCA cycle: Series of reactions, resulting in 2CO2 molecules, 1 ATP, and energy-carrying molecules.

    Oxidative Decarboxylation of Pyruvate

    • Occurs in the mitochondrial matrix.
    • Pyruvate is converted into acetyl CoA, CO2, NADH and H⁺, through the action of pyruvate dehydrogenase.
    • Products feed into the TCA cycle.

    Tricarboxylic Acid (TCA) Cycle

    • Also known as the citric acid cycle or Krebs cycle.
    • Acetyl-CoA is hydrolyzed to acetyl, a series of reactions occur, resulting in the formation of 2 CO2 and 1 ATP.

    Energy from Acetyl CoA

    • 3 NADH → 7.5 ATP
    • 1 FADH2 → 1.5 ATP
    • 1 GTP → 1 ATP
    • 10 ATP per oxidized acetyl CoA
    • NADH produced in the cytoplasm is not able to directly pass the mitochondrial membrane. Brain and muscle cells have a specific transport mechanism to get cytoplasmic NADH into the mitochondria and produce more ATP. The liver, heart, and kidney use a different transport mechanism to produce more ATP.

    Oxidative Phosphorylation

    • ATP is formed from the transfer of electrons from NADH and FADH2.
    • Takes place in the inner mitochondrial membrane.

    Anaerobic Respiration (In Plants)

    • Pyruvate + NADH + H+ → Ethanol + CO2 + NAD+.

    Anaerobic Respiration (In Animals)

    • Pyruvate is converted to lactate.
    • Reaction catalyzed by lactate dehydrogenase.

    The Cori Cycle

    • Cycle where lactate produced by anaerobic respiration in muscles is carried to the liver, converted back to pyruvate, and subsequently glucose.
    • This glucose is then used by the muscle cells.

    Glycogenolysis

    • The breakdown of glycogen into glucose.
    • Occurs in the liver and skeletal muscles.
    • It is NOT the reverse reaction of glycogen synthesis (glycogenesis).

    In-born Errors of Carbohydrate Metabolism

    • Genetic defects in enzymes involved in carbohydrate metabolism.
    • Examples: McArdle syndrome (glycogen phosphorylase deficiency) and Von Gierke disease (glucose-6-phosphatase deficiency).

    Pentose Phosphate Pathway

    • Also known as the hexose monophosphate shunt.
    • Occurs in the cytosol of cells.
    • Produces NADPH (needed for biosynthetic reactions, example steroid and fatty acid synthesis) and 5-carbon sugars (important for nucleotide synthesis).
    • Divided into two portions:
      • Oxidative reactions: Irreversible reactions.
      • Non-oxidative reactions: Reversible reactions.

    G6PD Deficiency

    • Glucose-6-phosphate dehydrogenase deficiency is a hereditary disease causing hemolytic anemia.
    • Reduced NADPH leads to a decrease in glutathione, resulting in damage to red blood cells and hemolysis.

    Gluconeogenesis

    • Synthesis of glucose from non-carbohydrate precursors.
    • Precursors include: lactate, glycerol, and certain amino acids.
    • Crucial for maintaining glucose levels during prolonged fasting or carbohydrate deprivation.
    • Requires specific enzymes in both the mitochondrial and cytosolic compartments
    • Key role in providing a continuous supply of glucose to areas such as the brain and active tissues like muscles.

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    Description

    Test your knowledge of metabolic reactions with this quiz focused on anabolic and catabolic processes, the role of coenzymes, and the TCA cycle. Explore questions about energy production, ATP generation, and the significance of various biochemical pathways. Perfect for students studying biochemistry!

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