Question 1

The oxygen binding by hemocyanins is mediated by

Accepted Answer

Hemocyanins bind oxygen through a pair of copper atoms, unlike hemoglobins which use an iron-containing heme group.

Question 2

Which of the following statements about the symmetry model of allosterism is not true?

Accepted Answer

All the statements (A, B, C, D) correctly describe aspects of the symmetry model of allosterism, which posits that allosteric proteins are oligomers with symmetric subunits that can exist in multiple conformations, with ligands able to bind to subunits in any conformation, and that the symmetry of the protein is maintained during conformational changes.

Question 3

The Bohr effect refers to

Accepted Answer

The Bohr effect describes how a decrease in blood pH (more acidic conditions) leads to a decrease in the affinity of hemoglobin for oxygen, facilitating oxygen release to tissues.

Question 4

Why is the decreased affinity of fetal hemoglobin for BPG advantageous?

Accepted Answer

Fetal hemoglobin needs to extract oxygen from maternal hemoglobin, which is high in BPG concentration. Therefore, decreased BPG binding biases the fetal hemoglobin towards the R state, which increases its oxygen affinity and enhances oxygen extraction from the mother's circulation.

Question 5

The most rapid way that erythrocytes adapt to high altitudes is

Accepted Answer

Erythrocytes adapt to high altitudes by increasing the intracellular concentration of 2,3-bisphosphoglycerate (BPG), which promotes the release of oxygen from hemoglobin molecules. This adaptation occurs rapidly, within a matter of days or weeks, and allows red blood cells to efficiently deliver oxygen to tissues despite the reduced partial pressure of oxygen at high altitudes. The other choices given, such as producing genetically modified hemoglobins or relying on myoglobin, are not known mechanisms of adaptation in erythrocytes at high altitudes.

Question 6

Max Perutz's investigation of the structure of hemoglobin primarily utilized_____.

Accepted Answer

Max Perutz utilized X-ray crystallography to investigate the structure of hemoglobin.

Question 7

The Hill plot shows that the fourth oxygen binds to hemoglobin with a ______-fold greater affinity than the first.

Accepted Answer

The Hill plot is used to describe cooperative binding in proteins such as hemoglobin. It shows that the binding affinity of hemoglobin for oxygen increases with each oxygen molecule that binds. Specifically, the fourth oxygen molecule binds with approximately 100-fold greater affinity than the first, illustrating the cooperative nature of oxygen binding to hemoglobin.

Question 8

The reaction of carbonic anhydrase catalyzes

Accepted Answer

Carbonic anhydrase catalyzes the hydration of carbon dioxide, forming bicarbonate and protons.

Question 9

What is the type of symmetry that relates the protomers in hemoglobin with respect to each other?

Accepted Answer

Hemoglobin has a quaternary structure composed of four subunits (two alpha and two beta chains) arranged with C2 symmetry, meaning it has a two-fold rotational axis.

Question 10

During the T to R conformational shift,Fe(II)drags the F-helix via a bond to the side chain of ________.

Accepted Answer

During the T to R conformational shift in hemoglobin, Fe(II) drags the F-helix via a bond to the side chain of His F8. This interaction is crucial for the conformational change that allows hemoglobin to switch between its oxygen-bound and oxygen-free states.

Question 11

Hemoglobin's p₅₀ value is about ______ as great as myoglobin's p₅₀ value.

Accepted Answer

Hemoglobin's p₅₀ value is approximately ten times greater than that of myoglobin, indicating that hemoglobin has a lower affinity for oxygen compared to myoglobin.

Question 12

When the partial pressure of O₂ in venous blood is 30 torr,the saturation of myoglobin with O₂ is ______ while the saturation of hemoglobin with O₂ is ______.

Accepted Answer

Myoglobin has a higher affinity for O2 and is nearly fully saturated at 30 torr, while hemoglobin is only partially saturated at this pressure.

Question 13

The rearrangement of T state hemoglobin to the R state

Accepted Answer

The movement of the Fe(II) ion into the heme plane is a key step in the rearrangement of T state hemoglobin to the R state. In the T state, the Fe(II) ion is pulled out of the heme plane towards the proximal His residue, making it less accessible to oxygen binding. In the R state, the Fe(II) ion moves back into the heme plane, making it more accessible to oxygen binding. This conformational change is responsible for the cooperative oxygen binding behavior of hemoglobin.

Question 14

While the binding of O₂ to myoglobin as a function of pO₂ is described by a simple __________ curve,thebinding to hemoglobin is described by a more complex ______ curve.

Accepted Answer

The binding of oxygen to myoglobin is described by a hyperbolic curve due to its single binding site, indicating a simple direct relationship between oxygen concentration and binding. In contrast, hemoglobin, which has multiple binding sites, exhibits cooperative binding, resulting in a sigmoidal curve that reflects the more complex relationship between oxygen concentration and binding.

Question 15

Some abnormal hemoglobins have Hill coefficients that are ______ that of normal hemoglobin,indicating that their ability to bind oxygen cooperatively has been compromised.

Accepted Answer

Hill coefficient is a measure of cooperativity of oxygen binding to hemoglobin. A value less than that of normal hemoglobin indicates compromised cooperative binding, meaning that the ability of the abnormal hemoglobin to bind oxygen cooperatively is reduced.

Question 16

Hemerythrin and hemocyanin are:

Accepted Answer

Hemerythrin and hemocyanin are oxygen transport proteins found in invertebrates. Hemerythrin is found in some marine invertebrates, while hemocyanin is found in arthropods and mollusks. Both proteins contain copper atoms, which bind and transport oxygen.

Question 17

The value of n,the Hill constant (coefficient),for hemoglobin is about ______ as great as the value for myoglobin.

Accepted Answer

The Hill constant (coefficient) represents the cooperativity of oxygen binding to the protein. Hemoglobin exhibits cooperative binding of oxygen which results in sigmoidal (S-shaped) oxygen dissociation curve, while myoglobin shows a hyperbolic oxygen dissociation curve which is indicative of non-cooperative binding. The Hill constant for hemoglobin is approximately 2.8, whereas for myoglobin it is approximately 1. So, the value of n for hemoglobin is about three times as great as the value for myoglobin.

Question 18

Which of the following increases the affinity of hemoglobin for O₂?

Accepted Answer

An increase in pH shifts the hemoglobin saturation curve to the left, indicating an increased affinity for oxygen. This is because a higher pH reduces the protonation of hemoglobin, which stabilizes the R (relaxed) state that has a higher affinity for oxygen.

Question 19

Consider a hypothetical hemoglobin-like molecule with a Hill coefficient (constant)of 1 and the same p₅₀ value as normal hemoglobin.Choose the statement below that best describes the two proteins.

Accepted Answer

The Hill coefficient is a measure of cooperativity in binding, with a value of 1 indicating no cooperativity. Therefore, the hypothetical hemoglobin does not exhibit cooperative binding. Both hemoglobins have the same p₅₀ value, indicating the same oxygen affinity. However, the hypothetical hemoglobin has a hyperbolic oxygen binding curve since it does not exhibit cooperativity, while normal hemoglobin has a sigmoidal curve due to cooperative binding. Therefore, statement C is the best choice. Statements A, B, D, and E are all false based on the information given.

Question 20

BPG stands for

Accepted Answer

BPG stands for bisphosphoglycerate, which is an important intermediate in glycolysis and is required for the release of oxygen from hemoglobin. Choice A (biphenylglycine) and D (bisphenylglycerol) are not commonly used acronyms in biochemistry. Choice B (boronylphenylglutamate) and E (betapropylglutamine) are not related to BPG nor commonly used in biochemistry.

Quiz 7: Protein Function Part I: Myoglobin and Hemoglobin

The oxygen binding by hemocyanins is mediated by

Which of the following statements about the symmetry model of allosterism is not true?

The Bohr effect refers to

Why is the decreased affinity of fetal hemoglobin for BPG advantageous?

The most rapid way that erythrocytes adapt to high altitudes is

Max Perutz's investigation of the structure of hemoglobin primarily utilized_____.

The Hill plot shows that the fourth oxygen binds to hemoglobin with a ______-fold greater affinity than the first.

The reaction of carbonic anhydrase catalyzes

What is the type of symmetry that relates the protomers in hemoglobin with respect to each other?

During the T to R conformational shift,Fe(II) drags the F-helix via a bond to the side chain of ________.

Hemoglobin's p₅₀ value is about ______ as great as myoglobin's p₅₀ value.

When the partial pressure of O₂ in venous blood is 30 torr,the saturation of myoglobin with O₂ is while the saturation of hemoglobin with O₂ is .

The rearrangement of T state hemoglobin to the R state

While the binding of O₂ to myoglobin as a function of pO₂ is described by a simple ____ curve,thebinding to hemoglobin is described by a more complex curve.

Some abnormal hemoglobins have Hill coefficients that are ______ that of normal hemoglobin,indicating that their ability to bind oxygen cooperatively has been compromised.

Hemerythrin and hemocyanin are:

The value of n,the Hill constant (coefficient) ,for hemoglobin is about ______ as great as the value for myoglobin.

Which of the following increases the affinity of hemoglobin for O₂?

Consider a hypothetical hemoglobin-like molecule with a Hill coefficient (constant) of 1 and the same p₅₀ value as normal hemoglobin.Choose the statement below that best describes the two proteins.

BPG stands for

Quiz 7: Protein Function Part I: Myoglobin and Hemoglobin

The oxygen binding by hemocyanins is mediated by

Which of the following statements about the symmetry model of allosterism is not true?

The Bohr effect refers to

Why is the decreased affinity of fetal hemoglobin for BPG advantageous?

The most rapid way that erythrocytes adapt to high altitudes is

Max Perutz's investigation of the structure of hemoglobin primarily utilized_____.

The Hill plot shows that the fourth oxygen binds to hemoglobin with a ______-fold greater affinity than the first.

The reaction of carbonic anhydrase catalyzes

What is the type of symmetry that relates the protomers in hemoglobin with respect to each other?

During the T to R conformational shift,Fe(II) drags the F-helix via a bond to the side chain of ________.

Hemoglobin's p50 value is about ______ as great as myoglobin's p50 value.

When the partial pressure of O2 in venous blood is 30 torr,the saturation of myoglobin with O2 is ______ while the saturation of hemoglobin with O2 is ______.

The rearrangement of T state hemoglobin to the R state

While the binding of O2 to myoglobin as a function of pO2 is described by a simple __________ curve,the binding to hemoglobin is described by a more complex ______ curve.

Some abnormal hemoglobins have Hill coefficients that are ______ that of normal hemoglobin,indicating that their ability to bind oxygen cooperatively has been compromised.

Hemerythrin and hemocyanin are:

The value of n,the Hill constant (coefficient) ,for hemoglobin is about ______ as great as the value for myoglobin.

Which of the following increases the affinity of hemoglobin for O2?

Consider a hypothetical hemoglobin-like molecule with a Hill coefficient (constant) of 1 and the same p50 value as normal hemoglobin.Choose the statement below that best describes the two proteins.

BPG stands for

Hemoglobin's p₅₀ value is about ______ as great as myoglobin's p₅₀ value.

When the partial pressure of O₂ in venous blood is 30 torr,the saturation of myoglobin with O₂ is while the saturation of hemoglobin with O₂ is .

While the binding of O₂ to myoglobin as a function of pO₂ is described by a simple ____ curve,thebinding to hemoglobin is described by a more complex curve.

Which of the following increases the affinity of hemoglobin for O₂?

Consider a hypothetical hemoglobin-like molecule with a Hill coefficient (constant) of 1 and the same p₅₀ value as normal hemoglobin.Choose the statement below that best describes the two proteins.