Transport of oxygen in the blood

Question 1

How are erythrocytes specialised for their function?

Answer 1

• Biconcave so increases SA:Vol ratio
• Small + flexible to pass through capillaries
• No nucleus for more haemoglobin

Question 2

What is the consequence of erythrocyte adaptations?

Answer 2

RBCs only survive 120 days so are constantly being replaced by red bone marrow

Question 3

What is the process that makes RBCs?

Answer 3

Haematopoiesis

Question 4

What is the protein that carries oxygen?

Answer 4

Haemoglobin

Question 5

Describe the structure of haemoglobin:

Answer 5

• Globular conjugated protein
• 4 peptide chains
• Contains prosthetic group (haem) which contains iron
• Each Hb molecule can bind to 4 O2 molecules

Question 6

What does positive cooperativity mean?

Answer 6

Haemoglobin molecules change shape, making it easier for next 2 O2 molecules to attach

Question 7

What is the reaction that takes place between haemoglobin + oxygen?

Answer 7

Haemoglobin + oxygen -> Oxyhaemoglobin

Question 8

What does partial pressure of O2 (pO2) mean?

Answer 8

Its a measure of O2 conc

Greater the conc of dissolved O2, higher the partial pressure

Question 9

Explain the process of transporting O2 in the lungs:

Answer 9

1. RBCs enter lungs, O2 levels low in RBC
2. Partial pressure of O2 is high in alveoli
3. This creates steep conc gradients
4. O2 moves from alveoli into blood + binds with haemoglobin

O2 bound to haemoglobin keeps free O2 conc low, maintaining diffusion gradients until all haemoglobin saturated

Question 10

Why is there a short diffusion pathway in alveoli?

Answer 10

Squamous epithelium tissues line alveoli, which are thin

Question 11

What is the impact of the alveoli having a dense network of capillaries?

Answer 11

Blood flow helps maintain diffusion gradients

Question 12

Explain the process of transporting O2 at the tissues:

Answer 12

1. Blood reaches tissues
2. Conc of O2 in cytoplasm of cells is lower than in erythrocytes
3. Partial pressure of O2 low in tissues
4. Oxyhaemoglobin readily gives up O2 to these cells, + it dissociates

Question 13

What does an oxygen dissociation curve show?

Answer 13

The affinity (attraction between Hb + O2) of haemoglobin for oxygen

Important for understanding how blood carries + releases O2

Question 14

Explain what happens on a oxygen dissociation curve:

Answer 14

• If partial pressure of O2 is high, haemoglobin has high affinity for O2 + binds to it (e.g. lungs)
• If partial pressure of O2 low, (e.g. tissues) affinity of haemoglobin fir O2 is low + O2 dissociates from Hb and released to respiring cells in tissues

Question 15

Explain the Bohr effect:

Answer 15

At higher partial pressure of CO2, haemoglobin gives up O2 more easily

This change known as Bohr Effect - shift to right

Question 16

Why is the Bohr Effect important?

Answer 16

Since in tissues with high partial pressure of CO2, haemoglobin gives up O2 more readily

In lungs where CO2 in air is low, O2 binds to haemoglobin easily

Increases rate that O2 released, helpful in exercise

Question 17

What is fetal haemoglobin?

Answer 17

Has higher affinity for O2 than adult haemoglobin, so it removes O2 from maternal blood as they move past each other

Question 18

Why is fetal haemoglobin important?

Answer 18

Since if blood of fetus had same affinity for O2 as blood of mother, little/no O2 would be transferred to fetus

Question 19

Why is fetal haemoglobin a thing?

Answer 19

• When fetus developing, dependent on mother for O2
• Oxygenated blood from mother runs close to deoxygenated fetal blood in placenta