Erythrocyte Structure and Function

Question 1

What size are RBCs?

Answer 1

6-8 micrometres

Question 2

Why do RBCs not have a nucleus?

Answer 2

So that they have more room for haemoglobin

Question 3

What is the structure of haemoglobin?

Answer 3

Four protein globin chains (two alpha and two beta chains) each associated with a non-protein haem group containing iron

Question 4

What is the shape of a RBC and what function does this shape serve?

Answer 4

Biconcave disc which provides a larger surface area for gas exchange

Question 5

How many molecules of oxygen can bind to one haemoglobin molecule?

Answer 5

4

Question 6

How do RBCs fit through small capillaries which are smaller in diameter than the RBC?

Answer 6

RBCs have a flexible cytoskeleton to allow them to squeeze through small capillaries

Question 7

Where in the cell is haem synthesised and which vitamin is required in this synthesis process?

Answer 7

The mitochondria

Vitamin B12

Question 8

How does adult haemoglobin vary from foetal haemoglobin?

Answer 8

Adult haemoglobin has 2 alpha globin chains and 2 beta globin chains. Foetal haemoglobin has 2 alpha globin chains and 2 gamma globin chains

Question 9

In what state is the iron in haemoglobin?

Answer 9

Ferrous (Fe3+)

Question 10

What is haemoglobin called when oxygen is bound to it?

Answer 10

Ocyhaemoglobin

Question 11

Describe the change in colour of haemoglobin when oxygen is bound compared to when oxygen is not bound.

Answer 11

Oxyhaemoglobin is bright red

Haemoglobin without oxygen is darker red

Question 12

What is the function of 2,3-DPG?

Answer 12

It allosterically promotes the release of oxygen from haemoglobin by decreasing the affinity of haemoglobin for oxygen

Question 13

How is oxygen taken up by RBCs in the lungs and released by RBCs in the respiring tissues?

Answer 13

The affinity of haemoglobin for oxygen is related to partial pressure of oxygen. Affinity is high when partial pressure is high in the lungs (causing binding) and affinity is low when partial pressure is low in the respiring tissues (causing release)

Question 14

In what form is carbon dioxide transported by haemoglobin and how is it changed to this form?

Answer 14

Carbon dioxide is converted to bicarbonate by the enzyme carbonic anhydrase in RBCs

Question 15

RBCs respire aerobically. T/F?

Answer 15

False - they respire anaerobically via the embden-myerhof pathway

Question 16

How many molecules pf ATP are gained by RBCs when they respire?

Answer 16

Net gain of ATP = 2

Question 17

What is the lifespan of a RBC?

Answer 17

120 days

Question 18

What is triggered by the release of nitric oxide by haemoglobin?

Answer 18

Local vasodilation to increase blood flow and oxygen supply to nearby cells.

Question 19

In the Embden-Meyerhof pathway what is glucose converted to?

Answer 19

Lactate