Question 1

Which statement best describes the primary physiological role of myoglobin compared to hemoglobin?

Accepted Answer

Myoglobin stores oxygen in muscle cells, while hemoglobin transports oxygen from the lungs to tissues.

Question 2

Which of the following best defines a holoprotein?

Accepted Answer

A protein with its prosthetic group bound.

Question 3

The heme group in myoglobin and hemoglobin contains which central atom, and what is its oxidation state when binding oxygen?

Accepted Answer

Iron in the +2 oxidation state.

Question 4

Which equation correctly represents the fraction of myoglobin bound to oxygen ($Y_{O_2}$) as a function of oxygen concentration $[O_2]$ and dissociation constant $K_d$?

Accepted Answer

$Y_{O_2} = \frac{[O_2]}{K_d + [O_2]}$

Question 5

If the $K_d$ for myoglobin binding oxygen is 2 mm Hg, what percentage of myoglobin is bound to oxygen at a $pO_2$ of 10 mm Hg?

Accepted Answer

83%

Question 6

Which of the following best describes positive cooperativity in hemoglobin?

Accepted Answer

Binding of one oxygen molecule increases the affinity for subsequent oxygen molecules.

Question 7

Which plot shape is characteristic of hemoglobin's oxygen binding curve, and what does it indicate?

Accepted Answer

Sigmoidal; indicates cooperative binding.

Question 8

Which of the following is an allosteric effector that stabilizes the T-state of hemoglobin and promotes oxygen release in tissues?

Accepted Answer

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

Question 9

A patient is exposed to high levels of carbon monoxide (CO). What is the biochemical consequence regarding hemoglobin function?

Accepted Answer

CO binds tightly and essentially irreversibly to hemoglobin, preventing oxygen binding and causing suffocation.

Question 10

Which of the following best explains the Bohr effect in hemoglobin?

Accepted Answer

Lower pH decreases hemoglobin's affinity for oxygen, promoting oxygen release.

Question 11

Which of the following is true regarding the Monod-Wyman-Changeaux (MWC) model of hemoglobin allostery?

Accepted Answer

Oxygen binding to one subunit increases the probability of the tetramer switching from the T-state to the R-state.

Question 12

Which of the following statements about myoglobin and hemoglobin structure is correct?

Accepted Answer

Myoglobin is a monomer, while hemoglobin is a tetramer composed of two alpha and two beta chains.

Question 13

Which of the following equations correctly represents the equilibrium constant ($K_d$) for myoglobin binding oxygen?

Accepted Answer

$K_d = \frac{[Mb][O_2]}{[MbO_2]}$

Question 14

Which of the following is a heterotropic allosteric effector of hemoglobin?

Accepted Answer

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

Question 15

A blood sample has a $pO_2$ of 30 mm Hg. What is the approximate percentage of hemoglobin saturated with oxygen in venous blood?

Accepted Answer

50%

Question 16

Which of the following best describes the difference in oxygen binding curves between myoglobin and hemoglobin?

Accepted Answer

Myoglobin displays a hyperbolic curve, while hemoglobin displays a sigmoidal curve.

Question 17

Which of the following scenarios would most likely increase oxygen unloading from hemoglobin in peripheral tissues?

Accepted Answer

Increased 2,3-BPG concentration and decreased pH.

Question 18

Which statement best describes the effect of 2,3-BPG on hemoglobin's oxygen affinity?

Accepted Answer

2,3-BPG stabilizes the T-state, decreasing hemoglobin's affinity for oxygen.

Question 19

Which of the following is true regarding the role of hemoglobin in carbon dioxide transport?

Accepted Answer

Carbon dioxide is carried back to the lungs by hemoglobin or in plasma as bicarbonate ($HCO_3^-$).

Question 20

A mutation causes hemoglobin to favor the R-state even at low oxygen concentrations. What is the most likely physiological consequence?

Accepted Answer

Decreased oxygen delivery to tissues due to reduced oxygen unloading.

Myoglobin and Hemoglobin: Oxygen Binding and Allostery

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