03.03 - Hemoglobin and Myoglobin

Question 1

Heme is a complex of ____________ and ____________.

Answer 1

Protoporphyrin IX, ferrous iron (Fe2+)

Question 2

Which of the following is not a function of heme?

a. Electron carrier in cytochromes
b. Part of the active site of catalase
c. Reversibly binds O2 in hemoglobin and myoglobin
d. None of the above

Answer 2

d. None of the above

Question 3

Which of the following statements about haemoglobin is incorrect?

a. It is found exclusively in RBCs.
b. It exists in two configurations.
c. It binds up to 2 oxygen molecules.
d. It can bind to carbon dioxide.

Answer 3

c. It binds up to 2 oxygen molecules.

Question 4

Fetal hemoglobin:

a. is composed of two alpha and two gamma subunits.
b. is synthesised in the bone marrow.
c. is produced starting the 8th month of gestation.
d. A and B

Answer 4

a. is composed of two alpha and two gamma subunits.

Question 5

Where is embryonal haemoglobin synthesised?

Answer 5

Yolk sac

Question 6

Where is feral haemoglobin synthesised?

Answer 6

Liver

Question 7

True or False: Hemoglobin A is synthesised starting the 8th month of gestation.

Answer 7

True

Question 8

Which of the following statements is incorrect?

a. The taut form of haemoglobin has low oxygen affinity.
b. Destruction of the salt bridges leads to the relaxed form of haemoglobin.
c. Binding of oxygen in one subunit will increase the binding of oxygen for the other haemoglobin subunits.
d. As oxygen binds to Hb, salt bridges are formed.

Answer 8

d. As oxygen binds to Hb, salt bridges are formed. (As oxygen binds to Hb, salt bridges are destroyed.)

Question 9

Which of the following does not describe myoglobin?

a. It functions in the storage of oxygen.
b. It consists of a single polypeptide chain composed of polar and non-polar amino acids.
c. Its serine residues play a role in oxygen binding.
d. An increase in Mb can be detected after a myocardial infarction.

Answer 9

c. Its serine residues play a role in oxygen binding. (Histidine residues are involved in oxygen binding.)

Question 10

At high oxygen pressure:

a. Mb is more saturated than Hb
b. Hb and Mb have low saturation
c. Both Hb and Mb are highly saturated
d. Information given is insufficient.

Answer 10

c. Both Hb and Mb are highly saturated

Question 11

As the partial pressure of oxygen decreases:

a. Hb releases oxygen easier than Mb
b. Mb releases oxygen easier than Hb
c. Hb and Mb releases oxygen at an equal rate
d. Both Hb and Mb are highly saturated

Answer 11

a. Hb releases oxygen easier than Mb

Question 12

Where is myoglobin found in the body?

Answer 12

Heart, muscles

Question 13

Which of the following pertains to haemoglobin?

a. Allosteric effects absent
b. Sigmoidal dissociation curve
c. One polypeptide chain
d. Hyperbolic curve

Answer 13

b. Sigmoidal dissociation curve

Question 14

True or False: Allosteric effects are absent in myoglobin.

Answer 14

True

Question 15

Which of the following factors will not cause a shift to the right of the oxygen dissociation curve?

a. carbon monoxide
b. 2,3 BPG
c. hypoxia
d. carbon dioxide

Answer 15

a. carbon monoxide

Question 16

When the oxygen dissociation curve shifts to the right, it means that:

a. There is increased attachment of haemoglobin to oxygen
b. Partial pressure of oxygen in the surrounding tissue increases
c. There is increased unloading of oxygen from haemoglobin
c. None of the above

Answer 16

c. There is increased unloading of oxygen from haemoglobin