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What is the primary function of hemoglobin?
What is the primary function of hemoglobin?
Myoglobin contains a single polypeptide chain of 153 amino acids.
Myoglobin contains a single polypeptide chain of 153 amino acids.
True
What metal complex is bound to heme in both hemoglobin and myoglobin?
What metal complex is bound to heme in both hemoglobin and myoglobin?
Ferrous iron (Fe2+)
The heme structure is formed by the linkage of four pyrrole rings through ______ bridges.
The heme structure is formed by the linkage of four pyrrole rings through ______ bridges.
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Match the following proteins with their primary roles:
Match the following proteins with their primary roles:
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Which statement about the structure of hemoglobin is correct?
Which statement about the structure of hemoglobin is correct?
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Which amino acid residue is coordinated to heme in myoglobin?
Which amino acid residue is coordinated to heme in myoglobin?
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Myoglobin can bind more than one molecule of O2.
Myoglobin can bind more than one molecule of O2.
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Both hemoglobin and myoglobin are vulnerable to poisoning from carbon monoxide (CO) or cyanide.
Both hemoglobin and myoglobin are vulnerable to poisoning from carbon monoxide (CO) or cyanide.
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What is the name of the deoxy form of hemoglobin?
What is the name of the deoxy form of hemoglobin?
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What structural feature allows myoglobin to function as a reservoir of oxygen in muscles?
What structural feature allows myoglobin to function as a reservoir of oxygen in muscles?
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In hemoglobin, the binding of O2 increases the affinity of remaining heme groups due to __________.
In hemoglobin, the binding of O2 increases the affinity of remaining heme groups due to __________.
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What affects hemoglobin's ability to bind O2?
What affects hemoglobin's ability to bind O2?
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The affinity for O2 is higher in hemoglobin than in myoglobin.
The affinity for O2 is higher in hemoglobin than in myoglobin.
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Name the gas that can significantly affect the oxygen affinity of hemoglobin.
Name the gas that can significantly affect the oxygen affinity of hemoglobin.
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Match the following components with their corresponding description:
Match the following components with their corresponding description:
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What is the primary function of hemoglobin’s cooperative binding of O2?
What is the primary function of hemoglobin’s cooperative binding of O2?
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2,3-Bisphosphoglycerate (2,3-BPG) increases the oxygen affinity of hemoglobin.
2,3-Bisphosphoglycerate (2,3-BPG) increases the oxygen affinity of hemoglobin.
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What is the term for the effect where the release of O2 is enhanced by lower pH levels in tissues?
What is the term for the effect where the release of O2 is enhanced by lower pH levels in tissues?
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About 15% of CO2 is carried as __________ bound to the N-terminal amino groups of hemoglobin.
About 15% of CO2 is carried as __________ bound to the N-terminal amino groups of hemoglobin.
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What adaptation occurs in red blood cells during high altitude conditions?
What adaptation occurs in red blood cells during high altitude conditions?
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What change occurs to carbon dioxide in the lungs during gas exchange?
What change occurs to carbon dioxide in the lungs during gas exchange?
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Match the hemoglobin type with its characteristic:
Match the hemoglobin type with its characteristic:
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Fetal hemoglobin (Hb F) contains two __________ chains instead of β-chains.
Fetal hemoglobin (Hb F) contains two __________ chains instead of β-chains.
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What is the primary component of Hemoglobin A2?
What is the primary component of Hemoglobin A2?
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Hb A1c is a product formed through enzymatic glycosylation of hemoglobin.
Hb A1c is a product formed through enzymatic glycosylation of hemoglobin.
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What condition is primarily diagnosed using Hemoglobin A2?
What condition is primarily diagnosed using Hemoglobin A2?
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In sickle cell anemia, episodes of ______, hyperbilirubinemia, and renal dysfunction are common symptoms.
In sickle cell anemia, episodes of ______, hyperbilirubinemia, and renal dysfunction are common symptoms.
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Match the following hemoglobinopathies with their symptoms:
Match the following hemoglobinopathies with their symptoms:
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What is the physiological significance of Hemoglobin A2?
What is the physiological significance of Hemoglobin A2?
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The presence of α-globin chains is unnecessary for synthesizing fetal hemoglobin (Hb F).
The presence of α-globin chains is unnecessary for synthesizing fetal hemoglobin (Hb F).
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How does sickle cell trait provide protection against malaria?
How does sickle cell trait provide protection against malaria?
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Study Notes
Hemoglobin Structure
- Composed of four polypeptide chains: two α chains and two β chains held together by non-covalent interactions.
- Each subunit contains α-helical structures and a heme-binding pocket similar to that of myoglobin.
Hemoglobin Function
- Hemoglobin binds to O2, H+, and CO2.
- Hemoglobin's O2 binding properties are affected by allosteric effectors.
Hemoglobin Conformations
-
T form (tense): Deoxyhemoglobin is in a tense state.
- Two αβ dimers interact via ionic and hydrogen bonds, restricting polypeptide chain movement.
- Low affinity for O2.
-
R form (relaxed): The structure relaxes upon O2 binding.
- Ionic and hydrogen bonds between αβ dimers break, allowing for polypeptide chain movement.
- High affinity for O2.
Myoglobin vs. Hemoglobin
- Myoglobin: Binds only one O2 molecule, exhibiting a hyperbolic binding curve.
- Hemoglobin: Binds four O2 molecules, exhibiting a sigmoidal binding curve.
Myoglobin & Hemoglobin Affinity for O2
- Myoglobin has a higher affinity for O2 than hemoglobin.
- Apoproteins create a hindered environment for heme iron.
CO Effect on Hemoglobin
- Carbon monoxide binds to hemoglobin with a higher affinity than oxygen.
- Carbon monoxide binding reduces oxygen-carrying capacity.
Cooperative Binding of O2 to Hemoglobin
- Binding of an oxygen molecule to one heme group increases the affinity of the remaining heme groups in the same hemoglobin molecule.
Allosteric Effects on Hemoglobin
- Allosteric effectors influence hemoglobin's ability to reversibly bind O2.
- Effectors include:
- pO2: Oxygen partial pressure.
- pH
- pCO2: Carbon dioxide partial pressure
- 2,3-Bisphosphoglycerate (2,3-BPG)
- Binding of these effectors affects O2 binding to heme groups.
pH and Hemoglobin
- Lower pH stabilizes the T state, enhancing oxygen delivery to tissues.
- In the lungs, the process reverses, and proton release facilitates CO2 exhalation.
pCO2 and Hemoglobin
- CO2 binds to hemoglobin, forming carbaminohemoglobin.
- CO2 binding stabilizes the T state, decreasing O2 affinity.
2,3-BPG and Hemoglobin
- 2,3-BPG is abundant in red blood cells and binds to deoxyhemoglobin, stabilizing the T conformation and decreasing O2 affinity.
Adaptation to High Altitude, Hypoxia, Anemia
- Increased 2,3-BPG concentration lowers oxygen affinity, promoting oxygen unloading in tissues.
Developmental Changes in Hemoglobin
- Fetal hemoglobin (Hb F): Two γ chains replace β chains, resulting in higher O2 affinity to facilitate oxygen transfer across the placenta.
- Hemoglobin A (Hb A): The major hemoglobin in adults.
- Hemoglobin A2 (Hb A2): Minor component of adult hemoglobin, useful for diagnosis.
- Hemoglobin A1c (Hb A1c): Glycosylated Hb A, used for monitoring diabetes mellitus.
Hemoglobinopathies
-
Sickle cell anemia: Genetic disorder caused by a point mutation in the β-globin gene.
- Deformed red blood cells leading to pain, hyperbilirubinemia, renal dysfunction, and increased susceptibility to infections.
-
β-Thalassemia: Genetic disorder causing defective β-globin synthesis.
- Leads to severe anemia requiring frequent blood transfusions.
-
α-Thalassemia: Genetic disorder causing defective α-globin synthesis.
- Severity depends on the number of affected α-globin genes.
Summary
- Hemoglobin is the oxygen-carrying protein in red blood cells, crucial for delivering oxygen to tissues and removing CO2.
- Its function is influenced by its structure and allosteric effectors.
- Binding of oxygen triggers conformational changes, resulting in a higher affinity for additional oxygen molecules.
- Genetic defects in hemoglobin can lead to serious diseases like sickle cell anemia and thalassemia.
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Description
Test your understanding of hemoglobin's structure, function, and conformations. This quiz covers the differences between hemoglobin and myoglobin, including their binding properties and structural changes. Delve into the roles of allosteric effectors and the importance of the T and R forms in oxygen transport.
