Biochemistry Chapter 8 Quiz
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Questions and Answers

What is the most common type of hemoglobin found in adults?

Hemoglobin A

What is the function of myoglobin?

Myoglobin is found in skeletal muscles and heart and serves as an oxygen storage protein.

What is the effect of increasing levels of 2,3-Bisphosphoglycerate (2,3 BPG) on oxygen affinity of hemoglobin?

  • No effect on oxygen affinity
  • Increases oxygen affinity
  • Decreases oxygen affinity (correct)

    • Which of these is a classic clinical manifestation of sickle cell anemia?

    <p>All of the above (D)</p> Signup and view all the answers

    Which type of thalassemia is characterized by a decreased or absent production of beta globin chains?

    <p>Beta thalassemia</p> Signup and view all the answers

    What is the name of the genetic disorder that causes sickle cell anemia?

    <p>Sickle cell anemia is caused by a single base substitution in the beta globin gene.</p> Signup and view all the answers

    Which of the following conditions can be a consequence of severe anemia in beta thalassemia major?

    <p>All of the above (D)</p> Signup and view all the answers

    Carbon monoxide binds to iron in heme with an affinity 240 times greater than oxygen.

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

    What is the name of the condition caused by an excess of methemoglobin?

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

    What is the treatment for methemoglobinemia?

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

    What is the primary reason sickle trait is protective against Plasmodium falciparum malaria?

    <p>Sickle cells cannot support the parasite's growth (D)</p> Signup and view all the answers

    What is the name of the condition in which red blood cells form crescents?

    <p>Sickle cell anemia</p> Signup and view all the answers

    Which of the following is NOT a common symptom of sickle cell disease?

    <p>All of the above are common symptoms of Sickle Cell Disease (E)</p> Signup and view all the answers

    What is the name of the condition that occurs when sickled red blood cells block small blood vessels?

    <p>Vaso-occlusion</p> Signup and view all the answers

    What is the term for the condition where the spleen, due to repeated infarctions, no longer functions effectively?

    <p>Functional asplenia</p> Signup and view all the answers

    What is the name of the drug that can help increase the amount of fetal hemoglobin (HbF) in patients with sickle cell disease?

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

    What is the name of the rare type of hemoglobin that is caused by a mutation in the beta globin gene, replacing glutamic acid with lysine?

    <p>Hemoglobin C</p> Signup and view all the answers

    Sickle cell trait does not protect against infection with Plasmodium falciparum malaria.

    <p>False (B)</p> Signup and view all the answers

    Which of the following genetic alterations is responsible for the development of sickle cell disease?

    <p>Single base substitution (B)</p> Signup and view all the answers

    Signup and view all the answers

    Flashcards

    Globular Proteins

    Proteins that are water-soluble and spherical in shape.

    Myoglobin

    A globular protein that binds oxygen in muscle tissue.

    Hemoglobin

    A globular protein in red blood cells that carries oxygen.

    Bohr Effect

    The phenomenon where increased CO2 and H+ reduce hemoglobin's affinity for oxygen.

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    Oxygen-Dissociation Curve

    Graph showing the relationship between O2 saturation and partial pressure of O2.

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    Hemoglobinopathies

    Genetic disorders affecting the structure and function of hemoglobin.

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    HbS

    Sickle cell hemoglobin, causing abnormal red blood cells.

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    HbC

    An abnormal hemoglobin variant that can lead to mild hemolytic anemia.

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    HbSC

    A combination of sickle cell and hemoglobin C disease.

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    Alpha Thalassemia

    A genetic condition where alpha globin chains are not produced properly.

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    Beta Thalassemia

    A genetic condition affecting the production of beta globin chains in hemoglobin.

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    Haldane Effect

    The property which describes how deoxygenation of hemoglobin increases its ability to bind CO2.

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    O2-Hb Dissociation Shift

    The change in the oxygen-binding curve due to varying CO2 and H+ levels.

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    CO2 Affinity

    The tendency of hemoglobin to bind to carbon dioxide.

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    Pulmonary Arteries

    Blood vessels that carry deoxygenated blood from the heart to the lungs.

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    Alveoli

    Tiny air sacs in the lungs where gas exchange occurs.

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    Deoxygenated Hemoglobin

    Hemoglobin that has released its bound oxygen.

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    Oxygenated Hemoglobin

    Hemoglobin that is currently bound to oxygen.

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    Shift Left

    Refers to the increase in hemoglobin's affinity for oxygen.

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    Study Notes

    Biochemistry 8

    • Globular proteins, hemoglobin and myoglobin structure and function
    • Bohr effect
    • Hemoglobinopathies

    Topics to be Learned

    • Globular hemeproteins
    • Myoglobin structure and function
    • Hemoglobin structure and function
    • Oxygen-dissociation curve and Bohr effect
    • Hemoglobinopathies (HbS, HbC, HbSC, alpha and beta thalassemias)
    • Topics cover pages 58-89 of the 8th edition of Lippincott Illustrated Reviews Biochemistry Textbook.

    Hemoglobin

    • Globin chains: Alpha (α), Beta (β), Gamma (γ), Delta (δ)
    • 4 chains in 2 pairs
    • Heme: Non-peptide molecule containing iron (Fe) and a porphyrin ring
    • Oxygen binds iron

    Hemoglobin Types

    • Hemoglobin A (HbA): α2β2 (95%)
    • Hemoglobin A2 (HbA2): α2δ2 (2-3%)
    • Hemoglobin F (HbF): α2γ2 (Fetal type)

    Oxygen-Hgb Dissociation Curves

    • Y-axis: Percentage of hemoglobin bound to oxygen
    • X-axis: Partial pressure of oxygen (pO2)

    Oxygen-Hgb Binding

    • Cooperative binding: Binding of one O2 molecule increases affinity for subsequent molecules
    • Positive cooperativity: Affinity for the last O2 molecule is 300 times greater than the affinity for the first molecule
    • S-shaped curve

    Allosteric Proteins

    • Allosteric site: "Other site" for binding, influencing binding at another site
    • Multi-subunit proteins
    • Hemoglobin is an allosteric protein
    • Positive allosteric effect: O2 cooperativity

    Hemoglobin Forms

    • Taut form (T): Releases O2, favored in tissues
    • Relaxed form (R): Holds onto O2, favored in lungs

    Peripheral Tissue (Bohr Effect)

    • COs are generated in tissues
    • CO2 + H2O ↔ H2CO3 ↔ HCO3– + H+
    • Oxygen delivery to tissues
    • Release of oxygen to tissues
    • Chloride shift (HCO3– enters the red blood cell in exchange for Cl- ions)

    O2 Affinity of Hb

    • Inversely proportional to CO2 and H+ concentrations
    • High CO2 and H+ lead to lower O2 affinity.

    Haldane Effect

    • Increased CO2 unloading in the lungs and increased O2 uptake.
    • Oxygenated hemoglobin has lower affinity for CO2 than deoxygenated hemoglobin
    • Shift to the left O2-Hb dissociation curve

    Shifts in O2-Hgb Curves

    • Hemoglobin's O2 affinity changes (not fixed)
    • Environment within red blood cells alters
    • Dissociation curves can shift to right or left

    Right Curve Shifts (Release O2)

    • Favors taut form
    • Causes: Rising metabolic activity (↑CO2), decrease in pH (↓pH), increase in temperature (↑Temp). Increases P50

    Left Curve Shifts (Latch on to O2)

    • Favors relaxed form
    • Causes: Lower metabolic activity (↓CO2), increase in pH (↑pH), decrease in temperature (↓Temp).

    2,3-Bisphosphoglycerate (2,3-BPG)

    • Found in red blood cells (RBCs)
    • Promotes O2 release from hemoglobin
    • Negative allosteric effector; increasing levels decrease Hb affinity for O2, increase O2 delivery to tissues
    • Produced from diverted 1,3 BPG from glycolysis
    • Increased levels are associated with high altitude, COPD and chronic anemia.

    Fetal Hemoglobin (HbF)

    • Predominant hemoglobin in the fetus, up to 90%
    • Higher oxygen affinity than adult hemoglobin (HbA). Necessary because fetal pO2 = 40 mmHg.
    • Left shift due to altered 2,3-BPG binding. 2,3-BPG binds poorly to gamma chains, increasing oxygen affinity.

    Myoglobin

    • Found in skeletal muscle and heart
    • Single polypeptide chain
    • High O2 affinity at all pressures
    • First binds oxygen

    Carbon Monoxide (CO)

    • Binds to iron in heme 240x more strongly than O2
    • Forms carboxyhemoglobin (HbCO), blocking O2 binding sites
    • Lower O2 carrying capacity = functional anemia
    • Left shift in oxyhemoglobin dissociation curve.

    Carbon Monoxide Poisoning

    • Nonspecific symptoms (headache, malaise)
    • Classic symptom (cherry-red lips)
    • Diagnosis involves carboxyhemoglobin level
    • Treatment: oxygen

    Methemoglobinemia

    • Small amount of iron in hemoglobin is oxidized from Fe2+ to Fe3+
    • Fe3+ (methemoglobin) cannot bind O2
    • Excess methemoglobin leads to hypoxia
    • Acquired from drugs (local anesthetics, nitric oxide, dapsone)
    • Treatment: methylene blue (reducing agent to convert Fe3+ to Fe2+)

    Clinical Scenario

    • Describes conditions associated with reduced O2 saturation or anemia

    Thalassemia

    • Decreased or absent production of globin chains
      • Alpha thalassemia: reduced α-globin production
      • Beta thalassemia: reduced β-globin production

    HbH Disease

    • Very little α-globin production
    • Excess β-globin
    • HbH forms: 4 β-chains
    • Easily damaged; much lower affinity for O2 than HbA
    • Associated with hypochromica, microcytic anemia leading to symptoms such as abnormal red blood cells' deformability, extravascular hemolysis, and elevated LDH.

    Hgb Barts

    • No α-globin production
    • Four γ-globin chains, causes severe fetal hemoglobinopathy.
    • Very high affinity for oxygen.

    Beta Thalassemia

    • Reduced β-globin synthesis
      • Beta Thalassemia Minor: Asymptomatic/mild anemia, detectable in routine blood work
      • Beta Thalassemia Major (Cooley's anemia): severe, chronic anemia leading to bone abnormalities

    Target Cells

    • Due to increased surface area to volume ratio.

    Extra-medullary hematopoiesis

    • Hematopoiesis outside the bone marrow
    • Often produces nucleated RBCs.

    Parvovirus B19

    • Infection can cause aplastic crises
    • Critically affects beta thalassemia major patients who depend on bone marrow for RBC production.

    Sickle Cell Anemia

    • Autosomal recessive disorder
    • Abnormal β-globin chains (HbS)
    • Makes up 95% of Hb
    • Single base substitution (adenine→thymine) in the sixth codon of β-globin gene.
    • Substitution of valine for glutamate in beta chains (valine is non-polar hydrophobic)
    • Deoxygenated HbS is poorly soluble, leading to sickling, polymerization and damage that leads to RBC deformability, extravascular hemolysis, and elevated LDH.
      • Leads to several complications: - Vaso-occlusion (may affect many organs, causing painful crises)
        • Increased risk of infections
        • Splenic failure
        • Increased HbF for treatment
          • Treatment: Hydroxyurea (increase HbF) Transfusion therapies Bone marrow transplant (potential cure)

    Sickle Cell Trait

    • One mutated beta globin gene
    • Normal beta gene is more effective

    • 50% HbS necessary for sickling

    Sickle Cell Diagnosis

    • Electrophoresis (showing HbS presence), special testing (sodium metabisulphite causing HbS precipitation), sickling testing: detects HbS by observing its insolubility in this specific environment.

    Malaria

    • Sickle cell trait provides protective effect against plasmodium falciparum, as cells sickle when infected, promoting faster clearance.
    • Does not eliminate malaria entirely
    • Effective in certain parts of Africa.

    HbC

    • Rare genetic mutation.
    • Different from sickle cell anemia.
    • Glutamic acid replaced by lysine.
    • Heterozygotes have mild anemia; extravascular hemolysis.
    • Presence of HbC crystals is detectable in blood smears. Induces red blood cell dehydration, increasing MCHC.

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    Biochemistry 8 PDF - Globular Proteins, Hemoglobin and Myoglobin

    Description

    Test your knowledge on the structure and function of globular proteins, particularly hemoglobin and myoglobin. This quiz covers critical topics such as the Bohr effect, hemoglobinopathies, and the oxygen-dissociation curve as described in the 8th edition of Lippincott Illustrated Reviews Biochemistry. Prepare to dive deep into the fascinating world of hemoglobin types and their roles in oxygen transport.

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