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Glycogen Metabolism Overview Quiz
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Glycogen Metabolism Overview Quiz

Created by
@VeritableJadeite

Questions and Answers

What is the preferred energy source for the brain?

  • Glucose (correct)
  • Amino acids
  • Fatty acids
  • Ketones

    • Which of the following is NOT a primary source of glucose?

  • Dietary intake of disaccharides
  • Monosaccharides from fruits
  • Glycogen degradation from liver
  • Lactate produced during anaerobic glycolysis (correct)

    • How does insulin affect glucose levels in the body?

  • It inhibits glucose uptake into cells.
  • It increases glucose production in the liver.
  • It promotes the storage of glucose in fat tissues.
  • It decreases glucose levels by increasing cellular uptake. (correct)

    • What role does glucagon play in glucose metabolism?

    <p>It raises blood glucose levels by stimulating glycogen breakdown.</p> Signup and view all the answers

    Which cells require glucose as their energy source due to the absence of mitochondria?

    <p>Mature red blood cells</p> Signup and view all the answers

    In what scenario is glycogen rapidly released from the liver?

    <p>In the absence of a dietary glucose source</p> Signup and view all the answers

    What is the effect of glucagon on heart muscle cells?

    <p>It stimulates glycogen breakdown.</p> Signup and view all the answers

    What happens to cAMP levels when insulin is released?

    <p>Insulin reduces cAMP levels following an initial increase.</p> Signup and view all the answers

    Which of the following carbohydrates is considered a glucose precursor?

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

    In the absence of gluconeogenic pathways, how long can the body rely on glycogen stores?

    <p>Approximately 12 hours</p> Signup and view all the answers

    What is the role of glycogen synthase in glycogenesis?

    <p>It exists in two forms, a more active form and a less active form.</p> Signup and view all the answers

    Which statement correctly describes the 'a' form of glycogen synthase?

    <p>It does not require glucose-6-phosphate for its activity.</p> Signup and view all the answers

    What effect does glucagon have on glycogen metabolism in the liver?

    <p>It reduces glycogenesis by activating adenylate cyclase.</p> Signup and view all the answers

    What happens to cAMP levels in response to insulin secretion?

    <p>Insulin activates phosphodiesterase, leading to decreased cAMP levels.</p> Signup and view all the answers

    Which enzyme is primarily affected by high concentrations of glucose-6-phosphate?

    <p>Glycogen synthase</p> Signup and view all the answers

    Which of the following correctly describes the effect of phosphorylation on glycogen synthase?

    <p>Phosphorylation inactivates glycogen synthase.</p> Signup and view all the answers

    How does insulin affect the levels of glycogenolysis and glycogenesis?

    <p>Insulin enhances glycogenesis while decreasing glycogenolysis.</p> Signup and view all the answers

    What is the primary effect of the inhibition of glycogenesis by the cAMP-directed pathway?

    <p>Decreased activity of glycogen synthase due to phosphorylation.</p> Signup and view all the answers

    Which factor primarily activates adenylate cyclase in liver cell membranes?

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

    What is the nature of the 'b' form of glycogen synthase?

    <p>It is dependent and inactive due to phosphorylation.</p> Signup and view all the answers

    What is the main effect of the calcium-calmudulin complex on liver phosphorylase kinase?

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

    Which hormones are mainly involved in the activation of glycogen degradation in the liver?

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

    How does AMP contribute to glycogenolysis in muscle tissue?

    <p>By activating phosphorylase b without phosphorylation.</p> Signup and view all the answers

    What is the primary purpose of glycogenolysis?

    <p>To maintain glucose homeostasis by breaking down glycogen</p> Signup and view all the answers

    What role does cAMP play in glycogen metabolism?

    <p>It activates adenylate cyclase.</p> Signup and view all the answers

    Where does glycogenesis primarily occur when blood glucose levels are high?

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

    What is the consequence of phosphorylation on glycogen metabolism enzymes?

    <p>It leads to a conformational change affecting active site activity.</p> Signup and view all the answers

    Which pathway activates glycogen degradation?

    <p>cAMP-directed pathway</p> Signup and view all the answers

    Which statement about epinephrine's effect on muscle glycogen is correct?

    <p>It inhibits glycogen synthesis and promotes glycogen degradation.</p> Signup and view all the answers

    What triggers the activation of phosphorylase b in muscle tissue?

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

    Which hormones primarily stimulate glycogenolysis?

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

    Glycogen is composed of glucosyl units linked by which type of bonds?

    <p>α-1,4-glycosidic bonds</p> Signup and view all the answers

    What happens to glycogen metabolism when cAMP levels rise in the liver?

    <p>Glycogenolysis is stimulated while glycogenesis is inhibited.</p> Signup and view all the answers

    What is the overall effect of hormonal signals on glycogen metabolism?

    <p>Regulate both glycogen synthesis and degradation.</p> Signup and view all the answers

    What is the role of cAMP in glycogen metabolism?

    <p>It activates glycogen degradation and inhibits glycogen synthesis</p> Signup and view all the answers

    How often do α-1,6-branches occur in glycogen?

    <p>Roughly every 8 to 10 glucosyl units</p> Signup and view all the answers

    What is the result of activating glycogen phosphorylase b in muscle?

    <p>Increased formation of glucose from glycogen.</p> Signup and view all the answers

    Which of the following is true regarding the location of glycogenolysis?

    <p>Primarily occurs in the liver and muscle</p> Signup and view all the answers

    What describes the function of lysosomal degradation of glycogen?

    <p>It is essential for the complete breakdown and recycling of glycogen</p> Signup and view all the answers

    Which of the following compounds is primarily involved in energy storage in animal cells?

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

    Which of the following best describes the role of glycogen in metabolism?

    <p>It serves as a readily available source of glucose during fasting.</p> Signup and view all the answers

    In which organ is glycogen primarily synthesized and stored?

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

    During glycogenolysis, which enzyme is responsible for the breakdown of glycogen?

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

    Which of the following signals is most influential in stimulating glycogen breakdown?

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

    What effect does insulin have on glycogen metabolism?

    <p>It promotes glycogen synthesis.</p> Signup and view all the answers

    Study Notes

    Glycogen Metabolism Overview

    • Glycogen serves as the primary storage form of glucose, composed of glucosyl units linked by α-1,4-glycosidic bonds, with branches formed by α-1,6 linkages every 8 to 10 units.
    • Essential for energy storage derived from carbohydrates; glycogen can be rapidly released from the liver and kidneys in the absence of dietary glucose sources.
    • Majorly degraded in exercising muscle to provide energy.

    Glycogenolysis (Degradation of Glycogen)

    • Involves shortening of glycogen chains and removal of branches, facilitating glucose homeostasis.
    • Converts glucose 1-phosphate to glucose 6-phosphate to regulate blood glucose levels.
    • Lysosomal degradation of glycogen aids in maintaining energy balance.

    Regulation of Glycogen Synthesis and Degradation

    • Glycogen degradation is activated by cAMP-directed pathways, especially during low glucose levels.
    • Glycogenesis occurs when blood glucose is high, predominantly in the liver and muscles.
    • Hormones like glucagon and epinephrine stimulate glycogenolysis, primarily in the liver.

    Key Hormones and Their Functions

    • Insulin: Lowers cAMP levels, enhancing glucose uptake into cells, and boosts glycogen synthesis.
    • Glucagon: Raises cAMP levels, activates glycogenolysis, and is active on heart muscle but not skeletal muscle.
    • Epinephrine (Adrenaline): Increases cAMP levels in muscle, promoting glycogenolysis and inhibiting glycogenesis.

    Key Enzymes in Glycogen Metabolism

    • Glycogen Synthase:
      • Exists in active “a” form (dephosphorylated) and inactive “b” form (phosphorylated).
      • Insulin promotes the activation of glycogen synthase, enhancing glycogenesis.
    • Glycogen Phosphorylase:
      • Activated in muscle by AMP, promoting glycogenolysis without phosphorylation.

    Coordination of Glycogen Synthesis and Degradation

    • Both processes are regulated by hormonal signals such as epinephrine, which enhances glycogenolysis while inhibiting glycogenesis through an increase in cAMP levels.
    • Phosphorylation of key enzymes by kinases alters their activity, influencing metabolic pathways.

    Primary Sources of Glucose

    • Dietary intake: includes starches, monosaccharides (like fructose), and disaccharides (such as lactose, maltose, sucrose).
    • Glycogen degradation: occurs rapidly from liver and kidney reserves when dietary glucose is unavailable.
    • Gluconeogenesis pathways support glucose levels for about 12 hours in fasting states.

    Implications of Glycogen Storage Diseases

    • Impairments in glycogen metabolism can lead to storage diseases affecting liver and muscle function, highlighting the importance of proper regulation in maintaining energy homeostasis.

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    Description

    Test your knowledge on glycogen metabolism, including the processes of glycogenolysis and glycogenesis. Understand how glycogen serves as a vital energy source and its regulation in the body. Challenge yourself with questions that cover the structure, function, and hormonal influences on glycogen.

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