RBC Metabolism and Membrane Physiology

Question 1

Embden-Meyerhof Pathway

Answer 1

-anaerobic pathway of glucose 
metabolism
- Glucose -> Pyruvate -> Lactate
- produces 90% of RBC energy
-consumes 2 ATP, makes 4 ATP = net 2 ATP

Question 2

Glycolysis Diversion Pathways

Answer 2

• Hexose monophosphate pathway (shunt)
• Methemoglobin reductase pathway
• Rapoport-Luebering pathway

Question 3

Hexose monophosphate pathway (shunt)

Answer 3

DETOXIFIES and protects RBC from oxidative stress.

• aka pentose phosphate shunt
• Prevents accumulation of H2O2 which prevents oxidation of iron to ferric 3+ state
• also prevents formation of methemoglobin
• uses G6PD to make G6P into PP.
• NADP reduced to NADPH which then reduces GSSG to GSH

Question 4

Methemoglobin reductase pathway

Answer 4

Heme iron is constatnly expossed to oxygen, an oxidizing agent. Meaning ferrous iron (2+) is oxidized to ferric state (3+) = methemaglobin which can’t carry oxygen.
NADPH + methemoglobin reductase reduce methemoglobin.

Question 5

Rapoport-Luebering Pathway

Answer 5

Generates 2, 3- BPG (2,3 DPG) which is important in oxygen delivery to tissues.

Question 6

What is the most common RBC enzyme deficiency?

Answer 6

G6PD deficiency

Question 7

What compromises deformability?

Answer 7

• age

- above 36% mean cell hemoglobin concentration

Question 8

Deformability

Answer 8

• RBC can stretch 2.5 times its resting diameter.
• Can pass through narrow capillaries and splenic pores.
• lose of property = can’t pass through splenic pores = RBC destroyed by splenic macrophages

Question 9

RBC Selective Permeability

Answer 9

• impermeable to Na, K, and Ca

- permeable to H2O, Cl, and HCO3

Question 10

Role of calcium

Answer 10

stabilizes cell and regulates RBC permeability

Question 11

Cation Pump

Answer 11

helps control salt gradient so the the cell doesn’t lyse

-Ion regulated via concentration gradient

Question 12

RBC Membrane

Answer 12

• Lipid bi layer (w. cytoskeleton)
• semi-permable
• RBC antigens on glycophorin
• 40% lipid, 52% protein, 8% carbs
• Spectrin/ankyrin = major cytoskeletal proteins

Question 13

What are the major cytoskeletal proteins of RBC membrane?

Answer 13

spectrin and ankyrin