Cell Metabolism and Fermentation Quiz
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Questions and Answers

What is produced during the oxidative phase of the Pentose Phosphate Pathway?

  • ATP and G-6-P
  • ADP
  • NADPH and a Pentose (correct)
  • R-5-P and CO2

    • Which statement correctly describes glycolysis?

  • It yields less than 500 kJ/mol of glucose.
  • Glycolysis does not occur in aerobic conditions.
  • Glycolysis occurs only in plant cells.
  • Pyruvate is the end product of glycolysis. (correct)

    • Which pathway is primarily responsible for generating NADPH?

  • Gluconeogenesis
  • Pentose Phosphate Pathway (correct)
  • Glycolysis
  • Citric Acid Cycle

    • What is the end product of glycolysis under anaerobic conditions?

    <p>Lactic Acid</p> Signup and view all the answers

    In the Pentose Phosphate Pathway, what does the nonoxidative phase regenerate?

    <p>Glucose-6-Phosphate from Ribulose-5-Phosphate</p> Signup and view all the answers

    What is the role of hexokinase in relation to glucose affinity?

    <p>It has a higher glucose affinity to ensure proper nutrient use.</p> Signup and view all the answers

    What does a high Km value indicate about an enzyme's affinity?

    <p>The enzyme has a low affinity for the substrate.</p> Signup and view all the answers

    How does the increase in reactants affect product formation?

    <p>It promotes activation, increasing product formation.</p> Signup and view all the answers

    What are the possible fates of pyruvate under anaerobic conditions?

    <p>It can be transformed into ethanol or lactate.</p> Signup and view all the answers

    Which molecule must be reoxidized for glycolysis to continue?

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

    What is the primary purpose of gluconeogenesis?

    <p>To synthesize new glucose from non-carbohydrate sources.</p> Signup and view all the answers

    What happens when there is an increase in product concentration?

    <p>It results in inhibition, decreasing product formation.</p> Signup and view all the answers

    What is the result of using ATP in the cell during energy-requiring processes?

    <p>It provides energy for essential metabolic reactions.</p> Signup and view all the answers

    What is the primary reason glucose-dependent cells, such as RBCs, cannot undergo oxidative phosphorylation?

    <p>They lack mitochondria.</p> Signup and view all the answers

    How does glucagon affect fructose 2,6-bisphosphate levels during fasting?

    <p>It decreases fructose 2,6-bisphosphate levels.</p> Signup and view all the answers

    Why can't the brain utilize amino acids during prolonged fasting?

    <p>They cannot cross the blood-brain barrier.</p> Signup and view all the answers

    What triggers gluconeogenesis when glucose levels are low?

    <p>A decrease in glucose concentrations.</p> Signup and view all the answers

    Which of the following is a precursor for gluconeogenesis?

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

    What role do glucogenic amino acids play in metabolism?

    <p>They contribute to the citric acid cycle.</p> Signup and view all the answers

    Why can animals not convert fatty acids into glucose?

    <p>The only product from fatty acids is acetyl-CoA, which cannot be converted to glucose.</p> Signup and view all the answers

    Which steps in glycolysis are irreversible and cannot be easily reversed for gluconeogenesis?

    <p>Conversion of pyruvate to acetyl-CoA.</p> Signup and view all the answers

    In which part of the body does gluconeogenesis primarily occur?

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

    During the energy use of the heart muscle, what is expected to activate phosphofructokinase 1?

    <p>Activation of fructose 2,6-bisphosphate.</p> Signup and view all the answers

    Which enzyme is primarily responsible for the conversion of pyruvate to oxaloacetate?

    <p>Pyruvate carboxylase.</p> Signup and view all the answers

    Which compound cannot be synthesized from acetyl-CoA in animals?

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

    What is a significant disadvantage of gluconeogenesis?

    <p>It requires high amounts of ATP.</p> Signup and view all the answers

    During gluconeogenesis, which compound is NOT an end product?

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

    What is the main reason that gluconeogenesis is not simply a reversal of glycolysis?

    <p>Some steps in glycolysis are irreversible due to high energy barriers.</p> Signup and view all the answers

    Which of the following statements about ATP generation in gluconeogenesis is true?

    <p>No ATP is generated during gluconeogenesis.</p> Signup and view all the answers

    Which of the following amino acids are classified as glucogenic?

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

    What is the primary role of glycerokinase in gluconeogenesis?

    <p>To convert glycerol to glycerol 3-phosphate</p> Signup and view all the answers

    Which of the following statements about Acetyl-CoA is correct?

    <p>It activates pyruvate carboxylase.</p> Signup and view all the answers

    What metabolic pathway is activated by fructose-1,6-bisphosphatase?

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

    Which cofactor is necessary for propionyl CoA carboxylase to function?

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

    Which of the following is true regarding the regulation of gluconeogenesis?

    <p>AMP inhibits gluconeogenesis.</p> Signup and view all the answers

    What is the end product of the conversion of methyl malonyl CoA in gluconeogenesis?

    <p>Succinyl CoA</p> Signup and view all the answers

    How is glycerol converted into an intermediate that can enter glycolysis?

    <p>By being converted into dihydroxyacetone phosphate (DHAP).</p> Signup and view all the answers

    Study Notes

    Lactic Acid Fermentation

    • Involves the conversion of carbohydrates into lactic acid, primarily by certain bacteria and fungi.
    • Plays a critical role in energy production under anaerobic conditions.

    Cori Cycle

    • A metabolic pathway that recycles lactate produced during anaerobic glycolysis back to glucose in the liver.

    Pentose Phosphate Pathway (PPP)

    • Functions as an alternative to glycolysis, generating NADPH and ribose-5-phosphate for nucleotide synthesis.
    • Two main phases:
      • Oxidative phase produces NADPH and a pentose sugar.
      • Non-oxidative phase regenerates glucose-6-phosphate from ribose-5-phosphate.
    • Significant connection to NADPH in combating oxidative stress.
    • Clinical relevance highlighted by glucose-6-phosphate dehydrogenase (G6PD) deficiency.

    Glycolysis Review

    • Central metabolic pathway for glucose oxidation across all tissues, yielding approximately -2840 kJ/mol of energy.
    • Glucose is essential for energy production and serves as a precursor for various metabolic pathways.
    • Results in the production of pyruvate as the end product.
    • Key outputs include:
      • 4 ATP, needed for energy-requiring cellular processes.
      • 2 NADH, which must be reoxidized to continue glycolysis.

    Regulation of Glycolysis

    • Heavily regulated to ensure effective nutrient use and ATP production.
    • Hexokinase is characterized by higher affinity for glucose; high Km values indicate low affinity.

    Gluconeogenesis

    • Synthesizes glucose from non-carbohydrate precursors to supply glucose-dependent cells (e.g., RBCs).
    • Vital during prolonged fasting, particularly for brain function which relies predominantly on glucose.
    • Energetically expensive, operating primarily in the liver.

    Pyruvate Fates

    • Under anaerobic conditions, pyruvate can convert to either lactate or ethanol (not in humans).
    • Transformation of pyruvate is contingent on environmental oxygen levels.

    Gluconeogenesis Precursors

    • Uses lactate, pyruvate, and oxaloacetate as substrates.
    • Glucogenic amino acids contribute by entering the citric acid cycle.
    • Fatty acids cannot be converted into glucose due to their metabolism producing acetyl-CoA, which cannot yield oxaloacetate.

    Differences Between Glycolysis and Gluconeogenesis

    • Their pathways are thermodynamically favorable, but they operate in reverse directions.
    • Involves several key enzymes that facilitate irreversible steps of glycolysis to form glucose.

    Enzymes in Gluconeogenesis

    • Notable enzymes include:
      • Pyruvate carboxylase converts pyruvate to oxaloacetate.
      • Phosphoenolpyruvate carboxykinase (PEPCK) further converts oxaloacetate to phosphoenolpyruvate.
      • Fructose-1,6-bisphosphatase regulates the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate.

    Reciprocal Regulation

    • Generally regulated by fluctuations in metabolites; increases in reactants stimulate product formation, while increases in products can inhibit further synthesis.
    • Key regulatory elements include citrate (activating gluconeogenesis) and AMP (inhibiting it), reflecting energy status in the cell.

    Additional Gluconeogenesis Sources

    • Glycerol, released from adipose tissue, can be converted to glucose; the process includes enzymes like glycerokinase and glycerol-3-phosphate dehydrogenase.
    • Propionate from odd-chain fatty acids and certain amino acids can also enter gluconeogenesis through conversion to succinyl-CoA before producing glucose.

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    Biochemistry LC6 Gluconeogenesis and Pentose Pathway PDF

    Description

    Test your knowledge on lactic acid fermentation, the Cori Cycle, and the Pentose Phosphate Pathway. This quiz covers the major metabolic pathways of glucose and their importance in organisms. Dive into the details of oxidative and nonoxidative phases, including their roles in generating NADPH.

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