Red Blood Cell Structure and Function
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Questions and Answers

What is the approximate diameter of a mature red blood cell (RBC)?

  • 2.0 μm
  • 7.5 μm (correct)
  • 10.0 μm
  • 1.0 μm

    • Which of the following is NOT a benefit of the biconcave shape of a mature RBC?

  • Increased resistance to haemolysis in hypotonic solutions
  • Enhanced deformability for passing through capillaries
  • Increased stability in hypertonic solutions (correct)
  • Increased surface area for gas exchange

    • Why is the deformability of red blood cells important?

  • It allows them to pass through narrow capillaries (correct)
  • It helps them bind to hemoglobin more effectively
  • It prevents them from breaking down in the bloodstream
  • It helps them transport oxygen more efficiently

    • What would happen to a red blood cell placed in a hypotonic solution?

    <p>It would swell and potentially lyse due to water gain (B)</p> Signup and view all the answers

    What is the main advantage of the biconcave shape of a mature RBC in terms of its function?

    <p>It increases the cell's surface area to volume ratio, allowing for faster gas exchange (C)</p> Signup and view all the answers

    What is the function of the G6PD enzyme in red blood cells?

    <p>Protection against oxidative stress (B)</p> Signup and view all the answers

    What is the primary reason for the biconcave shape of red blood cells?

    <p>To facilitate movement through narrow capillaries (B)</p> Signup and view all the answers

    What causes hereditary spherocytosis?

    <p>Mutations in cytoskeletal proteins like spectrin (C)</p> Signup and view all the answers

    What is the average lifespan of a red blood cell?

    <p>120 days (D)</p> Signup and view all the answers

    What is the primary function of red blood cells?

    <p>Transporting oxygen to tissues (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of red blood cells?

    <p>They contain a nucleus (B)</p> Signup and view all the answers

    What is the relationship between the volume of red blood cells and the hematocrit?

    <p>Hematocrit is the percentage of red blood cells by volume in whole blood (A)</p> Signup and view all the answers

    Why is the iron in hemoglobin maintained in the ferrous form (Fe2+)?

    <p>To promote oxygen binding (A)</p> Signup and view all the answers

    What enzyme in red blood cells catalyzes the reversible reaction between CO2 and H2O?

    <p>Carbonic anhydrase (A)</p> Signup and view all the answers

    What does a normal Mean Corpuscular Volume (MCV) range from?

    <p>80 to 95 fL (C)</p> Signup and view all the answers

    What percentage of CO2 transport in the blood is accounted for by carbaminohemoglobin?

    <p>23% (C)</p> Signup and view all the answers

    Which condition describes a red blood cell that is smaller than normal?

    <p>Microcytic (A)</p> Signup and view all the answers

    Which of the following best describes Mean Corpuscular Hemoglobin Concentration (MCHC)?

    <p>Actual hemoglobin concentration in red blood cells (B)</p> Signup and view all the answers

    What triggers hemoglobin to release oxygen in the tissues?

    <p>Decreased tissue PO2 (D)</p> Signup and view all the answers

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

    <p>Carry oxygen and CO2 (A)</p> Signup and view all the answers

    Which of the following statements is true regarding oxygen transport in the blood?

    <p>97% of oxygen is transported bound to hemoglobin (A)</p> Signup and view all the answers

    What is the primary function of hemoglobin in red blood cells?

    <p>To carry oxygen from the lungs to body tissues (C)</p> Signup and view all the answers

    Which of the following accurately describes methemoglobin?

    <p>Hemoglobin that contains Fe3+ ions (A)</p> Signup and view all the answers

    How does an increase in temperature affect hemoglobin's affinity for oxygen?

    <p>Decreases the affinity for oxygen (C)</p> Signup and view all the answers

    Which variety of hemoglobin contains two alpha and two beta chains?

    <p>Hemoglobin A (A)</p> Signup and view all the answers

    What is 2,3-bisphosphoglycerate (2,3-BPG) known to do in relation to hemoglobin?

    <p>Compete with oxygen for binding to deoxygenated hemoglobin (C)</p> Signup and view all the answers

    Which statement about fetal hemoglobin (Hb F) is true?

    <p>It allows for greater oxygen transport from the mother to the fetus (C)</p> Signup and view all the answers

    What characterizes sickle cell anemia in terms of hemoglobin composition?

    <p>Faulty beta chains with a valine substitution for glutamic acid (C)</p> Signup and view all the answers

    What happens when carbon monoxide binds to hemoglobin?

    <p>It forms carbon monoxyhemoglobin and reduces oxygen-carrying capacity (B)</p> Signup and view all the answers

    Which of the following modifications can occur in hemoglobin A1c?

    <p>Glucose attachment to the terminal valine of each beta chain (A)</p> Signup and view all the answers

    Which option correctly describes the subunit composition of hemoglobin A2?

    <p>Two alpha and two delta chains (C)</p> Signup and view all the answers

    Flashcards

    Mature RBC characteristics

    Mature red blood cells (RBCs) are circular biconcave disks, 7.5 μm in diameter, with a thickness of 2.0 μm and ≤ 1.0 μm in the center.

    Biconcave shape advantages

    The biconcave shape of RBCs allows for increased surface area, better gas exchange, and resistance to hemolysis in hypotonic solutions.

    Surface area vs volume

    RBCs' greater surface area relative to volume enables them to absorb more fluid and transport gases effectively.

    Deformability of RBCs

    RBCs exhibit remarkable deformability, allowing them to pass through small capillaries without rupturing.

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    Hypotonic solution effects

    In a hypotonic solution, RBCs can take in fluid without hemolyzing due to their biconcave shape and structure.

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    Fetal Blood Oxygen Carrying Capacity

    Fetal blood can carry more oxygen than maternal blood at the same blood PO2.

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    Carbonic Anhydrase Function

    An enzyme that catalyzes CO2 + H2O ↔ H2CO3 reaction, aiding CO2 transport.

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    Oxygen Transport by Hemoglobin

    97% of oxygen is transported when hemoglobin binds to O2 in the lungs.

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    Carbaminohemoglobin

    Hemoglobin that carries CO2, accounting for 23% of CO2 transport.

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    Mean Corpuscular Volume (MCV)

    Average volume of a single red blood cell, measured in cubic micrometers or fL.

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    Mean Corpuscular Hemoglobin (MCH)

    Average weight of hemoglobin in a single red blood cell, expressed in picograms (pg).

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    Mean Corpuscular Hemoglobin Concentration (MCHC)

    Percentage saturation of hemoglobin in red cells, measured in g/dL.

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    Types of Anemia Determined by RBC Indices

    Types of anemia assessed using MCV, MCH, and MCHC values.

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    Size of RBC

    The cell size decreases in subsequent stages of development.

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    Synthesis of Hemoglobin

    Process by which hemoglobin is formed; RBCs are anucleated to allow more space for Hb.

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    RBC Bi-concavity

    Shape of RBCs that allows them to squeeze through capillaries and maintain membrane tension.

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    RBC Metabolism

    RBCs perform anaerobic fermentation, having no mitochondria and only cytoplasmic enzymes.

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    G6PD Function

    Enzyme that helps prevent oxidative stress in RBCs by producing NADPH, an antioxidant.

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    Cytoskeleton of RBCs

    Structure that maintains the shape and flexibility of red blood cells' membranes; affected in hereditary spherocytosis.

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    Normal RBC Count

    Adult male RBC count ranges from 4.5 - 6.5 ×10^12/L; adult female from 3.9 - 5.6 ×10^12/L.

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    Hemoglobin Composition

    Hemoglobin in men averages 15 g/100 mL; women average 14 g/100 mL; each gram binds 1.34 mL O2.

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    Succinyl-CoA

    A compound that combines with glycine to form pyrrole in the Krebs cycle.

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    Protoporphyrin IX

    A molecule formed by four pyrroles, which combines with iron to form heme.

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    Hemoglobin

    A globular protein composed of four subunits, responsible for oxygen transport in red blood cells.

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    Methemoglobin

    Hb containing Fe3+ that appears dark-colored, formed from oxidation of hemoglobin.

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    Oxyhemoglobin

    Hemoglobin bound to oxygen, enabling oxygen transport in the blood.

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    Deoxyhemoglobin

    The state of hemoglobin without bound oxygen, often referred to as reduced hemoglobin.

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    2,3-bisphosphoglycerate (2,3-BPG)

    A metabolite that decreases hemoglobin's affinity for oxygen when present in higher concentrations.

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    Hemoglobin S

    An abnormal form of hemoglobin associated with sickle cell anemia, containing faulty beta chains.

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    Fetal hemoglobin (Hb F)

    A type of hemoglobin with two alpha and two gamma chains, allowing better oxygen transport from mother to fetus.

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    Hemoglobin A1c

    A form of hemoglobin with glucose attached, increased in poorly controlled diabetes mellitus.

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    Study Notes

    Red Blood Cell Structure and Function

    • Red blood cells (RBCs) are biconcave discs, 7.5 µm in diameter, 2.0 µm thick, and 1.0 µm in the center.
    • This shape maximizes surface area for efficient gas exchange (O2 and CO2).
    • RBCs are flexible, enabling them to pass through narrow capillaries.
    • This flexibility protects them from damage during circulation.
    • RBCs lack nuclei and mitochondria in mature form, maximizing space for hemoglobin.
    • They rely on anaerobic fermentation to generate ATP, unlike most other cells.

    RBC Cytoskeleton

    • The cytoskeleton maintains the shape and flexibility of RBC membranes.
    • Cytoskeletal proteins like spectrin, band 3, and ankyrin play a crucial role.
    • Mutations affecting these proteins, such as in hereditary spherocytosis, lead to abnormal shapes (spherical), trapping, and destruction, causing congenital hemolytic anemia.
    • The cytoskeleton is directly linked to the cell's shape and function.

    Hemoglobin (Hb)

    • Hemoglobin is a protein containing heme, an iron-containing porphyrin (iron porphyrin IX).
    • Globins combine with heme to form hemoglobin.
    • The oxygen-carrying protein (Hb) is a crucial component of RBCs.
    • Each hemoglobin is a globular molecule made up of four subunits.
    • Each heme group binds to an oxygen molecule.
    • 1 gram of Hb can combine with 1.34 mL of O2
    • Normal hemoglobin values: Men - 15 g of Hb/100 mL of cells , Women -14 g of Hb/100 mL.
    • Hb contains two alpha and two beta chains (α₂β₂).
    • A small amount (about 2.5%) is HbA2, substituting beta (β) chains with delta (δ) chains (α₂δ₂).
    • Hemoglobin A1c (HbA1c) has a glucose attached. High HbA1c levels indicate poorly controlled diabetes.
    • Hemoglobin S (HbS) has valine substituted for glutamic acid in the beta chains, resulting in sickle cell anemia.

    Fetal Hemoglobin (HbF)

    • HbF contains two alpha and two gamma chains (α₂γ₂).
    • HbF has a higher oxygen affinity than adult hemoglobin, crucial for fetal oxygen transport from the mother.
    • HbF is gradually replaced by HbA after birth.

    RBC Indices

    • MCV (Mean Corpuscular Volume): Average volume of a single RBC (µm³ or fL). Normal range: 80-95 fL.
    • MCH (Mean Corpuscular Hemoglobin): Average hemoglobin content per RBC (pg). Normal range: 27 to 34 pg.
    • MCHC (Mean Corpuscular Hemoglobin Concentration): Concentration of hemoglobin in a given volume of packed RBCs (g/dL). Normal range: 30-35 g/dL.
    • Important for diagnosing various anemias based on size and hemoglobin content of RBC's.

    RBC Function

    • Carry oxygen to tissues.

    • 97% of oxygen transport is in this way.

    • Carry carbon dioxide back to the lungs.

    • Approximately 23% is transported as carbaminohemoglobin

    • Act as an acid-base buffer.

    • Contain carbonic anhydrase, an enzyme that catalyzes the reversible reaction between CO2 + H2O ↔ H2CO3.

    • Maintain blood viscosity.

    • RBC count and blood indices (MCV, MCH, MCHC) are used to assess various hematologic conditions .

    RBC Production and Destruction

    • In adults, RBCs are produced in the bone marrow.
    • Lifespan is approximately 120 days.
    • Old RBCs are fragile and rupture in narrow blood vessels.
    • They are destroyed in the spleen.

    Regulation of Hemoglobin Affinity for Oxygen

    • Temperature, pH, and 2,3-BPG concentration influence Hb affinity.
    • High temperature and low pH lower Hb affinity, facilitating oxygen release to tissues.
    • 2,3-BPG is an important regulator influencing Hb’s affinity for O2.

    Other Important Factors

    • RBCs contain cytoplasmic enzymes, capable of metabolizing glucose, producing ATP, and maintaining membrane structure.

    • The maintenance of appropriate iron levels in ferrous form is paramount in reducing oxidative stress and preventing hemolysis.

    • G6PD deficiency weakens the ability of red blood cells to resist oxidative stress, leading to hemolysis and subsequent anemia.

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    Structure and Function of Red Blood Cells PDF

    Description

    This quiz explores the intricate details of red blood cells (RBCs), including their unique biconcave structure, flexibility, and the role of hemoglobin. It also discusses the cytoskeleton's impact on RBC shape, highlighting the significance of specific proteins and associated disorders. Test your knowledge on the essential functions and characteristics of these vital cells.

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