Red blood cells

Question 1

What is gone from the erythrocyte?

Answer 1

1. Nucleus
2. Mitochondria
3. Ribosomes

Question 2

What is the consequence of RBC being a simple cell?

Answer 2

1. No capacity for division or gene transcription.
2. No mitochondria= no TCA cycle so limited capacity to generate ATP.
3. No protein production= no damage repair= no apoptosis.

Question 3

What does the erythrocyte contain?

Answer 3

1. Haemoglobin
2. Water/solutes
3. Specialised membrane structures
4. Glycolytic enzymes- respiration via pumping
5. Surface proteins- blood groups

Question 4

How much haemoglobin does 1 RBC contain?

Answer 4

280million molecules of HbA. Also contain small amounts of HbF and HbA2

Question 5

What is HbF made of and what percentage of total Hb is it?

Answer 5

HbF is made of alpha chains and gamma chains. 0.5-0.8% is HbF

Question 6

What is HbA2 made of and what percentage of total Hb is it?

Answer 6

HbA2 is made of alpha and delta chains. 1.5-3.2% of haemoglobin is HbA2.

Question 7

Where is haem produced?

Answer 7

Mitochondria

Question 8

How does Iron bind oxygen?

Answer 8

A globin molecule surrounds the binding site by ionic interactions between protein chains. This allows just sufficient space of oxygen to enter.
As each oxygen is bound, the affitnity of the molecule for additional oxygen is increased (become constitutively more relaxed).

Question 9

How is oxygen entry controlled?

Answer 9

The shape of the entry point is controlled by globin to only allow oxygen through. Depending on how many ionic interactions are intact, the haemoglobin either has taut or relaxed formation.

Taut= oxygen entry is difficult, affinity is low.
Relaxed- entry is easier and affinity is high.

Question 10

O2-Hb disassociation curve shifts

Answer 10

Shift to the left= increased affinity for O2 (give up O2 less easily)
Shift to the right= decreased affinity for O2 (give up O2 easily)

Question 11

What does the normal position of the O2-Hb disassociation curve depend on?

Answer 11

Concentration of 2,3-DPG, H+ ions and CO2.

Question 12

Where is taut/relaxed formation good for?

Answer 12

Taut releases O2 so is good for tissues.

Relaxed absorbs O2 so is good for lungs.

Question 13

What are horizontal interactions and what do they do?

Answer 13

Ankyrin, 4.2, 4.1, Alpha and Beta spectrin and Tropomyosin.

They maintain the biconcave shape.

Question 14

What happens to RBCs in pyruvate kinase deficiency?

Answer 14

Cells lack the ATP to maintain correct osmolarity . Cells become spiky and are removed by the spleen.

Question 15

What happens to RBCs in G6P deficiency?

Answer 15

Pentose phosphate shunt cannot function properly so reducing power is not generated. Haemoglobin is damaged so it shrinks to one side producing hemighosts on the blood film.

Question 16

What are the energy-requiring processes in a mature RBC?

Answer 16

1. Initiation and maintenance of glycolysis.
2. Maintenance of cation concentrations (Cl- most important).
3. Maintenance of the red cell in biconcave form.

Question 17

What are the functions of the glycolytic pathway in the RBC?

Answer 17

1. NADPH production (Hexose monophosphate shunt)
2. ATP production (Emben-Myerhof pathway)
3. 2,3-DPG production (Rapaport- Luebering shunt)

Question 18

What is the function of the hexose monophosphate shunt?

Answer 18

1. Produce NADPH via G6PD which prolongs the life of the cell
2. It is a pool of reducing energy so iron and haemoglobin can function properly.
3. If the cell is under oxidative stress then the amount of glucose passing through the shunt can be increased to provide more reducing power.

Question 19

What is the function of the Emben-Myerhof pathway

Answer 19

• Produce ATP by metabolising glucose to lactic acid.
• Provides energy for maintenance of red cell volume, shape and flexibility.
• Also produces NADH needed by methaemoglobin reductase to reduce oxidised haemoglobin into functionally active haemoglobin.
• Uses 90-95% of glucose in the red blood cell.