Hematopoietic System Biochemistry 1

Question 1

What substance, when bound to heme, weakens the oxygen/heme bond and causes release of oxygen?

Answer 1

2,3-bisphosphoglycerate (2,3-bpg)

Question 2

Thiamine is also needed for what transketolase reaction?

Answer 2

The hexose monophosphate shunt. Thiamine is a cofactor needed for all transketolase reactions.

Question 3

What role does the hexose monophosphate shunt play in erythrocytes?

Answer 3

It produces NADPH which keeps glutathione in a reduced state. Glutathione is essential for RBCs to protect themselves against free-radical mediated damage

Question 4

Which enzyme is used along with the nadph to reduce glutathione in the erythrocyte?

Answer 4

Glutathione reductase

Question 5

What can bind to hemoglobin?

Answer 5

O2, CO2 and CO, H+, 2,3-bisphosphoglycerate

Question 6

What amino acid is needed to maintain the functionality and structure of the hemoglobin?

Answer 6

Histidine

Question 7

What are the three functions of hemoglobin?

Answer 7

Transport oxygen

Transport carbon dioxide

Act as a blood buffer

Question 8

What 2 substances are the starting materials for heme synthesis?

Answer 8

Succinyl-CoA and glycine

Question 9

Succinyl-CoA and glycine are the starting materials for heme synthesis.

What do they form?

Answer 9

Delta aminolevulinic acid

Question 10

What is the regulatory enzyme in heme synthesis?

Answer 10

Delta-aminolevulinic acid synthase (alas)

Question 11

The formation of porphobilinogen from Delta aminolevulinic acid is catalyzed by what enzyme?

Answer 11

Delta-aminolevulinic dehydrogenase (alad)

Question 12

What substance inhibits alad?

Answer 12

Lead

Question 13

What mineral is incorporated into heme?

Answer 13

Iron

Question 14

What mineral is incorporated into heme?
Where does this take place?

Answer 14

In the mitochondrion

Question 15

Where in the body does heme synthesis take place?

Answer 15

In the bone marrow

Question 16

Congenital deficiencies of certain enzymes in the heme synthesis can cause what?

Answer 16

Porphyrias

Question 17

In what other substances is heme found?

Answer 17

Myoglobin, cytochromes

Question 18

Where does catabolism of heme take place?

Answer 18

First the spleen, then the liver and finally the intestines. It also occurs in the bone marrow.

Question 19

What breaks down heme during tissue damage?

Answer 19

Macrophages

Question 20

What is the first substance produced by heme catabolism?

Answer 20

Biliverdin

Question 21

Biliverdin is converted into what molecule?

Answer 21

Bilirubin

Question 22

Where is bilirubin conjugated?

Answer 22

In the liver. Conjugating the bilirubin makes it water soluble.

Question 23

How is bilirubin excreted?

Answer 23

In the bile

Question 24

Bacteria in the gut convert some of the bilirubin into what substance?

Answer 24

Urobilinogen

Question 25

What is the fate of urobilinogen?

Answer 25

It is reabsorbed, transported to the kidneys and converted to urobilin and excreted

Question 26

What are the 2 excretory pathways for heme catabolism?

Answer 26

Feces and urine

Question 27

What role does H+ binding to hemoglobin have?

Answer 27

It induces hemoglobin to unload its bound oxygen and helps buffer blood pH