Red Blood Cell Metabolism Overview
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Questions and Answers

What is the primary function of red blood cells (RBCs)?

  • Transport oxygen from lungs to tissues (correct)
  • Produce hormones
  • Fight infections
  • Transport nutrients to cells

    • What cellular component do mature red blood cells lack?

  • Cell membrane
  • Ribosomes
  • Nucleus (correct)
  • Cytoplasm

    • How many ATP molecules are produced during glycolysis in red blood cells?

  • 1 ATP
  • 3 ATP
  • 2 ATP (correct)
  • 4 ATP

    • What is the role of NADPH in red blood cells?

    <p>Reduction of Fe3+ to Fe2+</p> Signup and view all the answers

    Which of the following statements regarding the structure of red blood cells is true?

    <p>RBCs are extremely flexible to pass through capillaries</p> Signup and view all the answers

    What type of transport do GLUT proteins utilize to move glucose across the plasma membrane?

    <p>Facilitated diffusion</p> Signup and view all the answers

    Which of the following statements about anaerobic glycolysis is true?

    <p>It produces lactate to regenerate NAD+</p> Signup and view all the answers

    What is the net energy yield in ATP from the anaerobic glycolysis of one glucose molecule?

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

    Which molecule is produced as a product of glycolysis that can be sent to the liver via the Cori cycle?

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

    What happens to GLUT proteins upon glucose binding?

    <p>They change conformation</p> Signup and view all the answers

    How many NADH molecules are generated for each glucose during anaerobic glycolysis?

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

    Which of the following best describes the process of facilitated diffusion utilized by GLUT 1?

    <p>Does not require ATP and is substrate-specific</p> Signup and view all the answers

    What is the primary function of lactate during anaerobic glycolysis?

    <p>To regenerate NAD+</p> Signup and view all the answers

    What is one of the main causes of acquired methemoglobinemia?

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

    Which agent is used in the treatment of methemoglobinemia?

    <p>Methylene blue</p> Signup and view all the answers

    What condition is characterized by an inability to bind oxygen effectively?

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

    What is a potential severe outcome if methemoglobinemia reaches more than 70% metHb?

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

    What genetic mutation is associated with congenital methemoglobinemia?

    <p>Mutations in the α- or β-globin chain</p> Signup and view all the answers

    Which population is known for a high incidence of a specific methemoglobinemia disorder?

    <p>Kentucky residents with close relative mating</p> Signup and view all the answers

    What effect does NADH-cytochrome b5 reductase deficiency have on hemoglobin?

    <p>Leads to iron oxidation</p> Signup and view all the answers

    Which of the following is NOT a symptom of methemoglobinemia?

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

    What is one of the roles of NADPH in biological systems?

    <p>Electron donor for the biosynthesis of cholesterol</p> Signup and view all the answers

    Which of the following substances does NADPH help neutralize?

    <p>Hydrogen peroxide (H2O2)</p> Signup and view all the answers

    Which enzyme utilizes electrons from NADPH in red blood cells to reduce oxidized glutathione?

    <p>Glutathione reductase</p> Signup and view all the answers

    In addition to biosynthesis, what major function does NADPH serve in the immune response?

    <p>Phagocytosis and destruction of pathogens</p> Signup and view all the answers

    What happens to NADPH levels in the case of G6PD deficiency?

    <p>NADPH production is reduced.</p> Signup and view all the answers

    Which biological process is NADPH NOT involved in?

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

    Which reactive oxygen species is not directly neutralized by NADPH?

    <p>Nitrate (NO3−)</p> Signup and view all the answers

    What role does NADPH play regarding cytochrome P450 monooxygenase?

    <p>It provides reducing equivalents for biotransformation processes.</p> Signup and view all the answers

    What is the primary cause of hemolytic anemia in patients with G6PD deficiency?

    <p>Oxidative stress from infections or medications</p> Signup and view all the answers

    Which of the following statements is true regarding the inheritance of G6PD deficiency?

    <p>It is an X-linked disorder mostly affecting males</p> Signup and view all the answers

    What characterizes the red blood cells (RBCs) of individuals with G6PD deficiency during oxidative stress?

    <p>Presence of Heinz bodies</p> Signup and view all the answers

    What percentage of enzyme activity is generally associated with asymptomatic G6PD deficiency?

    <blockquote> <p>60%</p> </blockquote> Signup and view all the answers

    How many distinct G6PD variants have been identified in the population?

    <p>More than 200</p> Signup and view all the answers

    What type of mutations are most commonly found in G6PD variants?

    <p>Point missense mutations</p> Signup and view all the answers

    What happens to RBCs in G6PD deficiency when oxidative stress occurs?

    <p>They undergo hemolysis</p> Signup and view all the answers

    Which factor primarily causes a reduction in NADPH levels in G6PD deficiency?

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

    Study Notes

    Red Blood Cell Metabolism Overview

    • Red blood cells (RBCs) lack mitochondria and only use glucose for energy production via glycolysis.
    • RBCs have a biconcave disc shape to maximize surface area for gas exchange and are flexible to pass through capillaries.
    • RBCs have a short lifespan of approximately 120 days and are constantly replaced.
    • RBCs produce only 2 ATP molecules per glucose molecule through glycolysis.

    Glycolysis

    • Glycolysis, the metabolic pathway used by RBCs, produces ATP, 2,3-bisphosphoglycerate (2,3-BPG), and converts Fe3+ to Fe2+ .
    • 2,3-BPG regulates oxygen affinity to hemoglobin.
    • Fe2+ is essential for oxygen binding to hemoglobin.

    Pentose Phosphate Pathway (PPP)

    • The PPP generates NADPH, which is essential for reducing oxidative stress in RBCs.

    Glucose Transporters: GLUT1

    • RBCs rely on GLUT1 transporters to facilitate glucose uptake.
    • GLUT1 transporters are present on the plasma membrane and function through facilitated diffusion, which is ATP-independent.

    RBC Energy Metabolism

    • Anaerobic glycolysis is the primary source of energy for RBCs.
    • Glycolysis yields 2 ATP, 2 NADH, and 2 pyruvate molecules per glucose molecule.
    • NAD+ is regenerated by converting pyruvate to lactate.
    • Lactate is transported to the liver for the Cori cycle.

    Methemoglobinemia

    • Methemoglobinemia occurs when iron in hemoglobin is oxidized to Fe3+, which cannot bind oxygen.
    • This condition can lead to tissue hypoxia and symptoms like anxiety, headache, and dyspnea.
    • Methemoglobinemia can be acquired due to oxidative stress or congenital deficiencies in NADH-cytochrome b5 reductase.
    • Treatment for methemoglobinemia involves using methylene blue, a reducing agent, to convert Fe3+ back to Fe2+.

    NADPH Biological Roles

    • NADPH plays crucial roles in various cellular processes, including biosynthesis of fatty acids, cholesterol, and steroids.
    • It neutralizes reactive oxygen species (ROS) like hydrogen peroxide, superoxide, and hydroxyl radical.
    • It provides reducing equivalents for cytochrome P450 monooxygenase systems involved in steroid biosynthesis and xenobiotic/drug detoxification.
    • It participates in phagocytosis, the destruction of pathogens by macrophages and neutrophils.
    • It is a substrate for nitric oxide (NO) synthesis.

    NADPH Role in RBC

    • NADPH is essential for maintaining the reduced form of glutathione (GSH), a major antioxidant in RBCs.
    • G6PD, the enzyme responsible for NADPH production in RBCs, plays a key role in protecting against oxidative stress.

    G6PD Deficiency

    • G6PD deficiency, an X-linked genetic disorder, results in reduced NADPH production, increasing oxidative stress and Heinz body formation.
    • Individuals with G6PD deficiency are typically asymptomatic unless exposed to triggers like infections or certain medications.
    • G6PD deficiency causes episodic hemolytic anemia.

    G6PD Deficiency Variants and Hemolysis

    • There are numerous G6PD variants, with over 200 mutations identified.
    • These mutations primarily involve point missense mutations affecting enzyme stability and kinetics.
    • Individuals with G6PD activity levels greater than 60% of normal are typically asymptomatic.

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    Description

    Explore the critical metabolic processes of red blood cells, including glycolysis and the pentose phosphate pathway. Learn how these processes influence ATP production, oxygen binding, and the overall function of RBCs in the body. This quiz covers key components such as glucose transporters and the lifespan of red blood cells.

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