Deck 10: Hemoglobin Metabolism

Question 1

Which of the following correctly describes the structure of normal hemoglobin A (Hb A)?

A) Four identical polypeptide chains, each containing two heme groups
B) Two $\alpha$ and two $\beta$ polypeptide chains, each containing one heme group
C) Conjugated protein with 141 amino acids, containing two atoms of iron
D) Two $\delta$ and two $\gamma$ polypeptide chains, each containing a single heme group

Answer 1

Two $\alpha$ and two $\beta$ polypeptide chains, each containing one heme group

Question 2

Where is heme produced?

A) Liver
B) Macrophages in the bone marrow
C) Red blood cell (RBC) precursors in the bone marrow
D) Mature RBCs in peripheral circulation

Answer 2

Red blood cell (RBC) precursors in the bone marrow

Question 3

Which of the following is true for the relative affinity of hemoglobin for oxygen in the lungs and tissue with the oxygen dissociation curve in its normal position? Lungs Tissue

A) High Low
B) Low Low
C) High High
D) low low

Answer 3

High Low

Question 4

Which of the following is true of hemoglobin if the oxygen dissociation curve shifts to the left?

A) Has a lower affinity for oxygen
B) Picks up less oxygen in the lungs but delivers more to tissues
C) Picks up more oxygen in the lungs but delivers less to tissues
D) Picks up and delivers more oxygen

Question 5

In which of the following conditions would patients have an increased concentration of methemoglobin?

A) Patient receiving drug containing sulfonamide
B) Patient exposed to reducing agents
C) Patient with hemoglobin S (Hb S)
D) Patient with methemoglobin reductase deficiency

Question 6

The reference range for hemoglobin concentration:

A) Is lower in a newborn than in a male adult
B) Is lower in a newborn than in a female adult
C) Is higher in a newborn than in a male adult
D) Is higher in a woman than in a man

Question 7

The A1_c modified component of Hb A is increased in what condition?

A) Sickle cell anemia
B) Thalassemia
C) Disorders of heme
D) Uncontrolled diabetes mellitus

Question 8

Identify the primary organelle of synthesis site for globin chain and heme in developing RBCs. Globin chains Heme

A) Ribosomes Ribosomes
B) Golgi complex Mitochondria
C) Ribosomes Mitochondria
D) Mitochondria Golgi complex

Question 9

Why is heme located inside a globin chain pocket surrounded by hydrophobic amino acids?

A) Protects iron from being oxidized to its ferric form
B) Necessary for oxygen release to tissues
C) Makes hemoglobin insoluble
D) Keeps heme from being dissolved

Question 10

Which of the following statements is true about Hb F?

A) It is the major hemoglobin during fetal life.
B) It is increased in concentration in children up to 2 years old.
C) It is evenly distributed at low concentration in all RBCs of an adult.
D) It has a low oxygen affinity.

Question 11

All of the following hemoglobins are found in a normal human adult except:

A) Hb A
B) Hemoglobin Gower-2
C) Fetal hemoglobin (Hb F)
D) Hb A₂

Question 12

Which of the following is true of the oxygen dissociation curve?

A) The normal partial pressure of oxygen (PO₂) at which hemoglobin is 50% saturated is 20 mm Hg.
B) A shift to the right or left in response to blood pH is called the Bohr effect.
C) A shift to the left results in lower oxygen affinity.
D) A shift to the right results in less effective delivery of oxygen to tissue.

Question 13

An increase in the concentration of 2,3-BPG:

A) Puts hemoglobin the relaxed conformation form
B) Shifts the oxygen dissociation curve to the left
C) Increases the affinity of hemoglobin for oxygen
D) Is present in patients with severe anemia and decreased blood pH (acidosis)

Question 14

Select the form of hemoglobin that contains iron in the ferric rather than the ferrous state.

A) Myoglobin
B) Methemoglobin
C) Deoxyhemoglobin
D) Carboxyhemoglobin

Question 15

Which of the following causes a shift to the right on the oxygen dissociation curve?

A) Severe anemia
B) Alkalosis
C) High levels of Hb F
D) Decreased levels of 2,3-biphosphoglycerate (2,3-BPG)

Question 16

Why is it important that synthesis of globin chains and heme be balanced in the RBCs?

A) Excess concentration of protoporphyrin increases bilirubin in plasma.
B) An excess of one of the components of hemoglobin decreases RBC survival.
C) An excess of one of the components of hemoglobin increases RBC survival leading to an eventual elevated RBC count.
D) An excess of globin chains significantly decreases the concentration of globin chain messenger ribonucleic acid (mRNA) in the developing RBCs.

Question 17

Which of the following provides a negative feedback for heme synthesis, thus helping to control, by decreasing, its synthesis?

A) Concentration of heme in the developing RBC
B) Concentration of hemoglobin in blood
C) Concentration of globin chain in the developing RBC
D) Number of RBCs in circulation

Question 18

How many molecules of oxygen can one molecule of hemoglobin carry?

A) One
B) Two
C) Three
D) Four

Question 19

Which of the following is true regarding carboxyhemoglobin?

A) Smokers have increased levels.
B) It has hydrogen sulfide added to hemoglobin.
C) Normal people have none.
D) Levels of 15% to 20 % cause coma and death.

Question 20

Why does Hb F have a higher oxygen affinity than adult hemoglobin?

A) Fetal blood has a higher pH than adult blood.
B) Fetal blood has a higher hematocrit than adult blood.
C) Body temperature is lower in fetus.
D) It is necessary to extract oxygen from the maternal blood supply.

Question 21

What is the effect of an increased concentration of 2,3-BPG in the RBC?

A) Puts hemoglobin in the relaxed conformation
B) Shifts the oxygen dissociation curve to the left
C) Increases the affinity of hemoglobin for oxygen
D) Decreases the synthesis of globin chains

Question 22

The globin chains making up Hb A are:

A) Two $\varepsilon$ and two $\gamma$ chains
B) Two and two $\varepsilon$ chains
C) Two $\alpha$ and two $\gamma$ chains
D) Two $\alpha$ and two $\beta$ chains