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Glucose Metabolism in Red Blood Cells
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Glucose Metabolism in Red Blood Cells

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Questions and Answers

What role does 2,3-bisphosphoglycerate play in relation to hemoglobin?

  • It is crucial for the release of O2 from hemoglobin. (correct)
  • It increases the production of ATP during glycolysis.
  • It is involved in the phosphorylation of glucose.
  • It regulates the conversion of pyruvate to lactate.

    • What is the consequence of arsenate poisoning on ATP production in glycolysis?

  • It enhances the overall glycolytic pathway efficiency.
  • It promotes the conversion of pyruvate to ATP.
  • It increases ATP yield through enhanced enzyme activity.
  • It bypasses step 7, leading to no net yield of ATP. (correct)

    • What is the primary role of insulin in glucose transport?

  • It decreases the number of GLUT 4 receptors.
  • It promotes rapid uptake of glucose by increasing GLUT 4 receptors. (correct)
  • It converts glucose to glucose-6-phosphate.
  • It inhibits glucose transporters.

    • Which enzyme is inhibited by glucose-6-phosphate?

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

    Which glucose transporter is primarily found in liver cells?

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

    What is the function of the enzyme 2,3-bisphosphoglycerate phosphatase?

    <p>It converts 2,3-BPG to 3-phosphoglycerate.</p> Signup and view all the answers

    Which of the following factors activates phosphofructokinase (PFK)?

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

    What happens when fructose-6-phosphate is present in high amounts?

    <p>It is converted to fructose-2,6-bisphosphate.</p> Signup and view all the answers

    In which type of cells are Na+-dependent co-transporters responsible for glucose transport located?

    <p>Intestinal and kidney cells</p> Signup and view all the answers

    What inhibits pyruvate kinase?

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

    What is the role of GLUT 4 in glucose regulation?

    <p>Facilitate glucose uptake in skeletal muscle and adipose tissues.</p> Signup and view all the answers

    What is produced when arseno-3-phosphoglycerate is hydrolyzed?

    <p>3-phosphoglycerate</p> Signup and view all the answers

    Which enzyme converts fructose-6-phosphate to fructose-2,6-bisphosphate?

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

    Which GLUT transporters are present in nearly all mammalian cells?

    <p>GLUT 1 and GLUT 3</p> Signup and view all the answers

    What is the effect of high levels of ATP on phosphofructokinase (PFK)?

    <p>It inhibits PFK.</p> Signup and view all the answers

    What happens to ATP production when step 7 of glycolysis is bypassed?

    <p>There is no net yield of ATP.</p> Signup and view all the answers

    Which of the following statements about GLUT transporters is true?

    <p>GLUT 7 transports glucose-6-phosphate to the ER.</p> Signup and view all the answers

    How does the transport of glucose occur via SGLT1?

    <p>It operates through secondary active transport mechanisms.</p> Signup and view all the answers

    Which of the following is a function of fructose-2,6-bisphosphate in glycolysis regulation?

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

    What does the presence of citrate indicate in the context of phosphofructokinase activity?

    <p>It indicates a high-energy state.</p> Signup and view all the answers

    What is the primary method by which red blood cells generate adenosine triphosphate (ATP)?

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

    Approximately what percentage of glucose in red blood cells is used to produce 2,3-bisphosphoglycerate (2,3-BPG)?

    <p>25%</p> Signup and view all the answers

    What is the function of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells?

    <p>Decrease oxygen affinity of hemoglobin</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of 1,3-bisphosphoglycerate to 2,3-bisphosphoglycerate in red blood cells?

    <p>Bisphosphoglycerate mutase</p> Signup and view all the answers

    How does red blood cells utilize the oxidative branch of the pentose phosphate pathway (PPP)?

    <p>To generate NADPH</p> Signup and view all the answers

    What role does glutathione play in red blood cells?

    <p>Oxidative stress defense</p> Signup and view all the answers

    What is the overall significance of glycolysis in red blood cells?

    <p>It is the primary pathway for ATP production.</p> Signup and view all the answers

    Which compound produced in glycolysis interacts with hemoglobin to modulate oxygen affinity?

    <p>2,3-bisphosphoglycerate</p> Signup and view all the answers

    What type of stress do red blood cells counteract using NADPH generated from the pentose phosphate pathway?

    <p>Oxidative stress</p> Signup and view all the answers

    What is the chemical structure interaction of 2,3-bisphosphoglycerate with hemoglobin?

    <p>It regulates the release of oxygen.</p> Signup and view all the answers

    Study Notes

    Glucose Metabolism in Red Blood Cells (RBCs)

    • RBCs exclusively utilize glycolysis for ATP production.
    • About 25% of glucose metabolized results in the synthesis of 2,3-bisphosphoglycerate (2,3-BPG), crucial for modulating hemoglobin's affinity for oxygen.
    • The pentose phosphate pathway (PPP) provides NADPH, essential for maintaining glutathione levels and combatting oxidative stress.

    Importance of Glycolysis in RBCs

    • 2,3-BPG acts as an allosteric effector that promotes oxygen release from hemoglobin.
    • Bisphosphoglycerate mutase catalyzes the conversion of 1,3-bisphosphoglycerate (1,3-BPG) to 2,3-BPG.
    • 2,3-BPG can be reversed to 3-phosphoglycerate, re-entering the glycolysis, consequently bypassing ATP production at step 7 while regulating oxygen release.

    Arsenate Poisoning Effects

    • Arsenate, a phosphorous analogue, replaces phosphate in 1,3-BPG, forming arseno-3-phosphoglycerate.
    • This compound hydrolyzes rapidly to 3-phosphoglycerate, leading to the bypassing of the glycolytic ATP-generating step.
    • Resulting in no net yield of ATP, which affects energy supply.

    Regulation of Glycolysis

    • Glucose transport into cells is the initial regulatory step, facilitated by specific transporters (e.g., GLUT family).
    • SGLT1 transports glucose via Na+-dependent co-transport in intestine and kidney cells.
    • GLUT 1 & GLUT 3 transport glucose across almost all mammalian cells, GLUT 2 is present in the liver, GLUT 4 is found in muscle and adipose tissue and is regulated by insulin, while GLUT 5 and GLUT 7 have specific functions in glucose and glucose-6-phosphate transport.

    Key Enzymatic Regulators

    • Hexokinase: Inhibited by glucose-6-phosphate; initiates glycolysis by converting glucose to glucose-6-phosphate.
    • Phosphofructokinase (PFK):
      • Inhibited by elevated ATP and citrate levels.
      • Activated by AMP and fructose-2,6-bisphosphate, signaling a need for glycolysis based on substrate availability.
    • Pyruvate Kinase:
      • Inhibited by ATP, indicating sufficient energy availability.
      • Activated by fructose-2,6-bisphosphate, enhancing glycolytic throughput.

    Additional Points on PFK Regulation

    • High fructose-6-phosphate levels are converted to fructose-2,6-bisphosphate through Phosphofructokinase-2 (PFK-2), promoting glycolysis.
    • Presence of fructose-2,6-bisphosphate enhances the glycolytic pathway, while FBPase-2 acts as a counter regulator, influencing the fructose-2,6-bisphosphate levels.

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    Description

    This quiz focuses on the metabolic pathways utilized by red blood cells, particularly glycolysis and the pentose phosphate pathway. Learn about the synthesis of 2,3-bisphosphoglycerate and its role in oxygen release. Additionally, explore the effects of arsenate poisoning on glucose metabolism in RBCs.

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