201 HI - Biochemistry

Question 1

What is the most common type of heme?

Answer 1

Heme B

Question 2

Organs involved in heme synthesis

Answer 2

Bone marrow

Liver

Question 3

Porphyria

Answer 3

Mostly genetic basis
Deficiency in heme synthesis enzymes → excessive porphyrins build-up & insufficient production of heme

Accumulation of heme precursors is the problem

Question 4

What forms heme B?

Answer 4

Glycine + Succinyl-CoA

Question 5

Heme synthesis:
Intiated & completed in ______;
Intermediate steps in ______

Answer 5

mitochondria; cytoplasm

Question 6

What is the most vital iron pool?

Answer 6

Transferrin

Question 7

Prostaglandins are derived from?

Answer 7

Arachidonic acid

Question 8

COX-1 vs COX-2

Answer 8

COX-1 constitutively expressed at low/baseline levels in almost all tissues (housekeeping)

COX-2 is rapidly inducible (by growth factors, cytokines, and endotoxins) and tightly regulated

Question 9

2 major functions of RBC

Answer 9

1. To carry O2 from the lung to the tissues and to aid in the return of CO2 from the tissues to the lung
2. To carry bases & nucleosides from the liver to other tissues

Question 10

Fuel of RBC

Answer 10

Glucose

Question 11

2 major RBC metabolic pathways

Answer 11

Fuel: glucose

Glycolysis
Hexose monophosphate shunt

Question 12

______ transports glucose through RBC membrane by facilitated diffusion

Answer 12

GLUT1

• insulin-independent

Question 13

3 functions of glycolysis

Answer 13

1. Generate energy
2. Reduction of methemoglobin
3. 2,3-BPG shunt

Question 14

What causes the conversion of hemoglobin to methemoglobin?

Answer 14

RBC rich in O2

Question 15

Glutathione is needed in?

Answer 15

Elimination of ROS

Question 16

Pyruvate kinase deficiency

Answer 16

Autosomal recessive

ATP depletion → Na+/K+ pump ↓

• loss of ion balance (swelling and lysis)
• triggers PK-deficient RBC’s destruction in the spleen

Increased 2,3-BPG due to metabolic block at PK step

Question 17

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Answer 17

X-linked recessive

Pentose phosphate pathway negatively affected

NADPH ↓ → ROS ↑:
Hemoglobin precipitate (Heinz bodies)
Membrane lipid peroxidation (hemolysis)

Bite cells & Heinz bodies

Question 18

Pyrimidine 5’ nucleosidase deficiency

Answer 18

Autosomal recessive

P5’NT (involved in RNA degradation in reticulocytes) activity is much higher in reticulocytes than mature RBCs and its activity rapidly declines after maturation

Question 19

Role of NADPH

Answer 19

Prevent ROS from damaging RBCs

Question 20

Cytochrome b5 reductase deficiency

Answer 20

Oxidation of Hb iron [Fe2+] → [Fe3+]
- Cannot bind O2

Chocolate cyanosis

Question 21

Familial 2,3-bisphosphoglycerate deficiency

Answer 21

Congenital polycythemia

Decrease in 2,3-BPG shifts the Hb oxygen dissociation curve to the left → decreased delivery of oxygen into the peripheral tissues

Body releases erythropoietin to compensate

Question 22

What shifts Hb oxygen dissociation curve to the left?

Answer 22

↓ temp
↓ 2,3 BPG
↓ pH

Question 23

What shifts Hb oxygen dissociation curve to the right?

Answer 23

↑ temp
↑ 2,3 BPG
↑ pH