W1-5 Hemoglobin

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Questions and Answers

What is the primary role of nonpolar interactions in the tertiary structure of myoglobin and hemoglobin?

Facilitating heme binding to the apoprotein

Enabling oxygen binding to the heme iron

Contributing to the stability of the protein structure (correct)

Promoting subunit interaction

Which interactions are involved in the binding of 2,3-bisphosphoglycerate to both adult and fetal hemoglobin?

Hydrogen bonds (correct)

Ionic bonds

Hydrophobic interactions

Covalent bonds

In which state does the iron need to be for oxygen binding to the heme iron in hemoglobin?

Oxidized state

Reduced state

Ferrous state (correct)

Ferric state

Which factor does NOT affect the oxygenation of hemoglobin in the lungs and in the tissues?

Nitric oxide (B) Signup and view all the answers

What is the result of mutations and deletions of globin genes that lead to disease?

Altered subunit structure (C) Signup and view all the answers

What is the therapeutic approach for carbon monoxide poisoning due to its competitive interaction with oxygen in hemoglobin?

Administering oxygen at high pressure (A) Signup and view all the answers

Which type of hemoglobinopathy is characterized by underproduction of one type of hemoglobin subunit?

Thalassemia (C) Signup and view all the answers

What is the point mutation in sickle cell anemia that leads to the substitution of Glu with Val at amino acid 6?

Mutation in Hb S (D) Signup and view all the answers

Which condition is characterized by significant fetal hemoglobin production continuing into adulthood, disregarding the normal shutoff point for adult-type hemoglobin?

Hereditary persistence of fetal hemoglobin (HPFH) (C) Signup and view all the answers

What type of mutation is associated with Hemoglobin Gun Hill?

Deletion mutation (D) Signup and view all the answers

In uncontrolled diabetes, which hemoglobin form can increase more than twice normal?

HbA1c (B) Signup and view all the answers

Which condition is characterized by chronic compensated hemolysis and an unstable mutant hemoglobin?

Hemoglobin Gun Hill (B) Signup and view all the answers

'Hb Barts' and 'HbH' are associated with which condition?

(α-thalassemia) (B) Signup and view all the answers

'HbE-Gower 1' and 'HbE Gower 2' are examples of which hemoglobinopathy?

(α-thalassemia) (D) Signup and view all the answers

'Hereditary persistence of fetal hemoglobin (HPFH)' is characterized by the continued production of which type of hemoglobin?

(hemoglobin F) into adulthood (A) Signup and view all the answers

'Thalassemia' results in underproduction of which type of hemoglobin subunit?

(α subunit) (D) Signup and view all the answers

What is the main structural difference between myoglobin and hemoglobin?

Myoglobin contains only 1 heme group while hemoglobin contains 4 heme groups (C) Signup and view all the answers

What is the significance of the steep slope in the oxygen binding curve of hemoglobin?

It allows hemoglobin to carry and deliver oxygen efficiently from sites of high pO2 to sites of low pO2 (D) Signup and view all the answers

What effect does 2,3-bisphosphoglycerate (2,3-BPG) have on the oxygen binding curve of hemoglobin?

It shifts the equilibrium between the R and T states toward the T, i.e., the low affinity form (C) Signup and view all the answers

What is one of the conditions that leads to an increase in 2,3-BPG concentration?

Chronic hypoxia, e.g., at high altitude (B) Signup and view all the answers

What effect does smoking have on the levels of 2,3-BPG in the blood?

Smoking reduces the levels of 2,3-BPG in the blood (D) Signup and view all the answers

How does carbon monoxide (CO) affect the oxygen binding curve of hemoglobin?

It changes the normal sigmoidal shape toward a hyperbola (B) Signup and view all the answers

In carbon monoxide (CO) poisoning, what is the first line of treatment?

Vitamin B12 administration (B) Signup and view all the answers

What is the structure of fetal hemoglobin (Hb F) compared to maternal Hb A?

Fetal Hb F has a higher affinity for O₂ and binds more strongly to 2,3-BPG than Hb A (C) Signup and view all the answers

Which unit is equivalent to 1 mm of mercury in a barometer?

'Torr' (C) Signup and view all the answers

What can cause an increase in methemoglobin levels in response to certain drugs, H2O2, free radicals or mutations?

Certain drugs, H2O2, free radicals or mutations (C) Signup and view all the answers

What are some factors that lead to an increase in 2,3-BPG concentration?

Chronic hypoxia at high altitude or chronic anemia (C) Signup and view all the answers

What is the main chemical difference between hemoglobin and methemoglobin?

The iron in hemoglobin is in the Fe2+ state, while in methemoglobin it is in the Fe3+ state (B) Signup and view all the answers

Which of the following is NOT a cause of methemoglobin formation?

Excessive oxygenation of blood (D) Signup and view all the answers

What is the primary role of the heme group in hemoglobin and myoglobin?

Bind oxygen reversibly (B) Signup and view all the answers

What structural feature is responsible for the movement of the iron atom and histidine residues in myoglobin upon oxygenation?

Hydrophobic interactions between the porphyrin ring and amino acid R-groups (B) Signup and view all the answers

Which type of hemoglobin has a tetrameric structure composed of two non-identical subunits?

HbA α2β2 (C) Signup and view all the answers

What is the function of the distal histidine in myoglobin and hemoglobin?

Assist in O2-binding (D) Signup and view all the answers

What effect does oxygenation have on the conformational state of hemoglobin?

"Relaxed" (R) state with high oxygen affinity (B) Signup and view all the answers

Which interactions are dominant and change little in the T-to-R conformational change of hemoglobin?

Inter-chain hydrophobic interactions (B) Signup and view all the answers

"HbE-Gower 1" and "HbE Gower 2" are examples of which condition?

"Thalassemia" (D) Signup and view all the answers

"Hereditary persistence of fetal hemoglobin (HPFH)" is characterized by the continued production of which type of hemoglobin?

"HbF α2g2" (A) Signup and view all the answers

Study Notes

Dr. Zahi Damuni is a Professor of Biochemistry, contact details provided for office hours and questions.
Learning objectives cover various aspects of myoglobin and hemoglobin, including their structures, oxygen binding, and the role of histidine residues.
Hemoproteins are a group of specialized proteins containing heme as a tightly bound prosthetic group, functioning as electron carriers, part of the active site of catalase, and binding oxygen reversibly.
Heme is a porphyrin ring with an iron atom at its center, forming covalent and coordinate bonds with the protein and oxygen.
Myoglobin is a monomeric heme protein found in skeletal and heart muscle with a predominantly non-polar interior and charged amino acids on the surface.
Myoglobin has a crevice that encloses a heme group, stabilized by hydrophobic interactions and hydrogen bonds.
Oxygenation of myoglobin leads to a conformational change and movement of the iron atom and His F8 towards the plane of the ring.
Hemoglobin is a tetrameric protein found mainly in RBCs with two non-identical subunits, each having a heme prosthetic group and going through structural changes upon oxygenation.
Hemoglobin exists in two stable states, a "taut" or "tense" state with low oxygen affinity and a "relaxed" state with high oxygen affinity.
Interactions between subunits in hemoglobin are dominated by hydrophobic and ionic interactions, with significant conformational changes upon oxygenation.
Each pair of alpha and beta subunits stays relatively in the same position under both oxygenated and deoxygenated states, but twist relative to each other.
Myoglobin and hemoglobin differ structurally, leading to their different functions: myoglobin binds and releases oxygen within muscle cells, while hemoglobin transports oxygen from the lungs to peripheral tissues and carbon dioxide from peripheral tissues to the lungs.
Oxygen binding curves for both myoglobin and hemoglobin show different shapes and behaviors: myoglobin has a hyperbolic curve with low oxygen delivery capacity, while hemoglobin demonstrates cooperative binding and high oxygen delivery capacity.
Binding of ligands like H+, CO2, and 2,3-bisphosphoglycerate affects hemoglobin's oxygen binding by shifting the equilibrium between the R and T states towards the T state, reducing oxygen saturation at a given partial pressure of oxygen.
Hemoglobin functions as a vehicle for delivering oxygen efficiently from sites of high partial pressure to sites of low partial pressure.
Myoglobin and hemoglobin have distinct structures, functions, and oxygen binding properties.

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Description

Learn about the structural differences and functional distinctions between myoglobin and hemoglobin, including their ability to bind oxygen molecules. Understand the unique characteristics of myoglobin and hemoglobin that contribute to their distinct physiological roles.