Hemoglobin Metabolism

Question 1

1. A hemoglobin molecule is composed of:
   a. One heme molecule and four globin chains
   b. Ferrous iron, protoporphyrin IX, and a globin chain
   c. Protoporphyrin IX and four globin chains
   d. Four heme molecules and four globin chains

Answer 1

d. Four heme molecules and four globin chains

Question 2

2. Normal adult Hb A contains which polypeptide chains?
   a. alpha and beta
   b. alpha and delta
   c. alpha and gamma
   d. alpha and epsilon

Answer 2

a. alpha and beta

Question 3

3. A key rate-limiting step in heme synthesis is suppression of:
   a. Aminolevulinate synthase
   b. Carbonic anhydrase
   c. Protoporphyrin IX reductase
   d. Glucose 6-phosphate dehydrogenase

Answer 3

a. Aminolevulinate synthase

Question 4

4. Which of the following forms of hemoglobin molecule has
   the lowest affinity for oxygen?
   a. Tense
   b. Relaxed

Answer 4

a. Tense

Question 5

5. Using the normal hemoglobin-oxygen dissociation curve in
   Figure 10-7 for reference, predict the position of the curve
   when there is a decrease in pH.
   a. Shifted to the right of normal with decreased oxygen
   affinity
   b. Shifted to the left of normal with increased oxygen affinity
   c. Shifted to the right of normal with increased oxygen
   affinity
   d. Shifted to the left of normal with decreased oxygen affinity

Answer 5

a. Shifted to the right of normal with decreased oxygen
affinity

Question 6

6. The predominant hemoglobin found in a healthy newborn is:
   a. Gower-1
   b. Gower-2
   c. A
   d. F

Answer 6

d. F

Question 7

7. What is the normal distribution of hemoglobins in healthy
   adults?
   a. 80% to 90% Hb A, 5% to 10% Hb A2, 1% to 5% Hb F
   b. 80% to 90% Hb A2, 5% to 10% Hb A, 1% to 5% Hb F
   c. .95% Hb A, ,3.5% Hb A2, 1% to 2% Hb F
   d. .90% Hb A, 5% Hb F, ,5% Hb A2

Answer 7

c. .95% Hb A, ,3.5% Hb A2, 1% to 2% Hb F

Question 8

8. Which of the following is a description of the structure of
   oxidized hemoglobin?
   a. Hemoglobin carrying oxygen on heme; synonymous
   with oxygenated hemoglobin
   b. Hemoglobin with iron in the ferric state (methemoglobin) and not able to carry oxygen
   c. Hemoglobin with iron in the ferric state so that carbon
   dioxide replaces oxygen in the heme structure
   d. Hemoglobin carrying carbon monoxide; hence “oxidized”
   refers to the single oxygen

Answer 8

b. Hemoglobin with iron in the ferric state (methemoglobin) and not able to carry oxygen

Question 9

9. In the quaternary structure of hemoglobin, the globin
   chains associate into:
   a. a tetramers in some cells and b tetramers in others
   b. A mixture of a tetramers and b tetramers
   c. a dimers and b dimers
   d. Two ab dimers

Answer 9

d. Two ab dimers

Question 10

10. How are the globin chain genes arranged?
    a. With a genes and b genes on the same chromosome,
    including two a genes and two b genes
    b. With a genes and b genes on separate chromosomes,
    including two a genes on one chromosome and one
    b gene on a different chromosome
    c. With a genes and b genes on the same chromosome,
    including four a genes and four b genes
    d. With a genes and b genes on separate chromosomes,
    including four a genes on one chromosome and two
    b genes on a different chromosome

Answer 10

b. With a genes and b genes on separate chromosomes,
including two a genes on one chromosome and one
b gene on a different chromosome

Question 11

11. The nature of the interaction between 2,3-BPG and hemoglobin is that 2,3-BPG:
    a. Binds to the heme moiety, blocking the binding of oxygen
    b. Binds simultaneously with oxygen to ensure that it stays
    bound until it reaches the tissues, when both molecules
    are released from hemoglobin
    c. Binds to amino acids of the globin chain, contributing
    to a conformational change that inhibits oxygen from
    binding to heme
    d. Oxidizes hemoglobin iron, diminishing oxygen binding
    and promoting oxygen delivery to the tissues

Answer 11

c. Binds to amino acids of the globin chain, contributing
to a conformational change that inhibits oxygen from
binding to heme