Gluconeogenesis Overview
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Questions and Answers

What is the primary role of glucogenic amino acids in metabolism?

  • They are used exclusively for energy production.
  • They are converted directly to fatty acids.
  • They serve as precursors for steroid hormones.
  • They are deaminated to form α-ketoacids. (correct)

    • In the Cori cycle, what is the primary function of lactate produced in the muscle?

  • It directly enters the citric acid cycle.
  • It is important for the formation of glycogen.
  • It is solely stored in muscle tissues for future energy use.
  • It is converted back to glucose in the liver. (correct)

    • What condition is often associated with fructose 1,6 bisphosphatase deficiency?

  • Severe liver damage from excess glucose.
  • High levels of insulin production and resistance.
  • Fasting hypoglycemia and lactic acidosis. (correct)
  • Weight gain due to increased fat storage.

    • Why are premature babies at risk for hypoglycemia?

    <p>They have immature nonfunctional enzymes for gluconeogenesis.</p> Signup and view all the answers

    What is a consequence of the Cori cycle's function in metabolism?

    <p>It prevents loss of lactic acid as a waste product.</p> Signup and view all the answers

    Which enzyme is responsible for converting pyruvate to oxaloacetate in gluconeogenesis?

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

    What is the role of fructose 1,6 bisphosphatase in gluconeogenesis?

    <p>Converts fructose 1,6 bisphosphate to fructose 6 phosphate</p> Signup and view all the answers

    Which of the following is NOT a gluconeogenic precursor?

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

    What is the main function of glucose 6-phosphatase in gluconeogenesis?

    <p>To catalyze the conversion of glucose 6-phosphate to glucose</p> Signup and view all the answers

    Which of the following gluconeogenic enzymes is NOT found in glycolysis?

    <p>Fructose 1,6 bisphosphatase</p> Signup and view all the answers

    Study Notes

    Gluconeogenesis

    • Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate precursors.
    • It is essential for maintaining blood glucose levels during fasting or starvation.
    • Three key irreversible reactions in glycolysis are bypassed in gluconeogenesis:
      • Hexokinase (or Glucokinase)
      • Phosphofructokinase
      • Pyruvate Kinase
    • Gluconeogenesis uses unique key enzymes distinct from glycolysis.

    Gluconeogenesis Key Enzymes

    • Pyruvate carboxylase converts pyruvate to oxaloacetate.
    • PEP carboxykinase converts oxaloacetate to phosphoenolpyruvate.
    • Fructose 1,6 bisphosphatase converts fructose 1,6 bisphosphate to fructose 6 phosphate.
    • Glucose 6-phosphatase converts glucose 6-phosphate to glucose.

    Gluconeogenic Precursors

    • Intermediates of glycolysis: These can be used to synthesize glucose.
    • Intermediates of the citric acid cycle: These can be converted to oxaloacetate and then to glucose.
    • Lactate: Lactic acid produced during anaerobic glycolysis in cells like red blood cells and skeletal muscles is transported to the liver and converted to glucose (Cori cycle).
    • Glycerol: Derived from triacylglycerol in adipose tissue, glycerol is converted to dihydroxyacetone phosphate (DHAP) and then to glucose.
    • Glucogenic amino acids: Deaminated to form α-ketoacids, which are then converted to pyruvate or citric acid cycle intermediates before being synthesized into glucose.

    Cori Cycle

    • The Cori cycle is a metabolic pathway involving the liver and muscles.
    • Muscles produce lactate during intensive exercise.
    • Lactate is transported to the liver and converted to glucose.
    • The newly synthesized glucose is returned to the muscles for energy production.

    Clinical Applications of Gluconeogenesis

    • Fructose 1,6 bisphosphatase deficiency: This genetic disorder leads to a deficiency in the enzyme responsible for the conversion of fructose 1,6 bisphosphate to fructose 6 phosphate. It results in fasting hypoglycemia and lactic acidosis.
    • Hypoglycemia in neonates: Premature babies are more susceptible to hypoglycemia due to their immature gluconeogenesis enzymes and low adipose tissue mass.

    Glucogenic Amino Acids

    • Glucogenic amino acids are those that can be converted into glucose via gluconeogenesis.
    • Examples include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, methionine, proline, serine, threonine, and valine.
    • These amino acids are often deaminated (removal of an amino group) to yield α-ketoacids, which can then enter the gluconeogenic pathway.

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    Related Documents

    Glucose Metabolism Lecture 4 PDF

    Description

    Explore the essential process of gluconeogenesis, which synthesizes glucose from non-carbohydrate precursors to maintain blood glucose levels. This quiz covers key enzymes involved in the process and how intermediates from glycolysis and the citric acid cycle contribute to glucose synthesis.

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