Hemoglobin Metabolism & Iron Metabolism

Question 1

What is the composition of Hgb and how is it synthesized?

Answer 1

Heme (w. Iron) + Globin

It is synthesized by heme + globin pairs of 2 alpha and 2 non-alpha to form the tetramer Hemoglobin.

Question 2

What are the different HgBs seen in the fetus?

Answer 2

Gower-1: Zeta + Epsilon
Gower-2: alpha + epsilon
Portland: zeta+gamma
F: alpha + gamma

Question 3

What are the different HgBs seen in a newborn?

Answer 3

F1: alpha + gamma
A1: alpha + beta

Question 4

What are the different HgBs seen in an adult?

Answer 4

A1: alpha + beta
A2: alpha + delta
F1: alpha + gamma

Question 5

Oxygen Dissociation Curve

Answer 5

P50 = 50% oxygen saturation when partial pressure of oxygen is 27 mm Hg.

Question 6

Oxygen Dissociation Curve: Left shift

Answer 6

shows reduced P50 which means higher oxygen affinity.

Caused by a decrease in 2,3-BPG, PCO2, temperature or an increase in pH.

Question 7

Oxygen Dissociation Curve: Right shift

Answer 7

shows increase P50 which means lower oxygen affinity.

Caused by an increase in 2,3-BPG, PCO2, temperature or an decrease in pH.

Question 8

Methemoglobin

Answer 8

iron is oxidized to Fe 3+ which means it cannot carry oxygen

Question 9

Sulfhemoglobin

Answer 9

addition of hydrogen sulfide irreversibly modifies hemoglobin = cannot carry oxygen.

Question 10

Carboxyhemoglobin

Answer 10

Higher affinity for carbon monoxide.

Question 11

Ferritin

Answer 11

major storage form of iron in enterocyte cytoplasm. (water soluble)

Question 12

Hemosiderin

Answer 12

Iron storage in macrophages (water-insoluble)

Question 13

What compounds enhance iron absorption?

Answer 13

1. Source/amount of iron in diet.
2. lower pH
3. Citrate + iron

Question 14

What compounds inhibit iron absorption?

Answer 14

1. tannins block absorption

2. dairy products interfer with Fe 3+ -> 2+ conversion.

Question 15

Hepcidin

Answer 15

regulates iron absorption by inhibiting iron release from hepatic stores.