Unit 4- Transport Of Gasses In Blood

Question 1

Describe the structure of a haemoglobin

Answer 1

A molecule of 4 polypeptide chains
At the centre of each chain is a haem prosthetic group
The haem group contains an iron atom which binds to an O2 molecule

Question 2

What is the equation for association of oxygen to haemoglobin?

Answer 2

Hb <== (+O2)(-H+)==> Hb(O2)

Oxygen is added and H+ is removed

Question 3

How is the oxygen binding site in haemoglobin cooperative?

Answer 3

Each molecule affects the binding of the next
The binding of one oxygen molecule triggers a small change in the shape in the haemoglobin to make it easier for the next O2 molecule to bind

Question 4

What can be said about haemoglobin affinity for oxygen?

Answer 4

At a low ppO2 haemoglobin has a low affinity for oxygen and at a high ppO2 haemoglobin has a high affinity for oxygen

Question 5

How can we measure the O2 saturation in the blood?

Answer 5

Colorimeter as oxygenated blood is pinky-red and deoxygenated blood is blue

Question 6

Explain the process of loading oxygen

Answer 6

In the alveoli of the lungs, oxygen rich air is constantly being brought in by ventilation, the there is a high ppO2.
So haemoglobin has a high affinity for O2, so binds becoming highly saturated

Question 7

Explain why O2 is unloaded at respiring tissues

Answer 7

Oxygen is used by respiration by respiring tissues, therefore low ppO2
Haemoglobin has a low affinity for O2 so unloads it

Question 8

Actively respiring tissues have a low pH, why is this and what is its affect?

Answer 8

• lots of production of CO2 from respiration
• CO2 dissolves in tissue fluid to become carbonic acid lowering pH
• Hydrogen ions drive the reaction towards the deoxyhaemoglobin state
• haemoglobin unloads the remaining O2

Question 9

What is the Bohr effect?

Answer 9

When a high conc of CO2 lowers the pH

This shifts the normal oxygen dissociation curve right, so haemoglobin always has a lower affinity for oxygen

Question 10

Where does the fetal haemoglobin load oxygen?

Answer 10

At the placenta where the mothers and fetus` capillary bed intertwines

Question 11

What is different about fetal haemoglobin?

Answer 11

• higher affinity for oxygen

- oxygen dissociation curve is shifted left

Question 12

What is the structure of myoglobin and where is it found?

Answer 12

Found in muscle cells only

- single polypeptide chain with a single haem group

Question 13

What is the function of myoglobin?

Answer 13

• stores oxygen
• has a super high affinity for oxygen (curve is shifted left)
• oxygen will only unload at very low ppO2 when the muscle cells are respiring a tonne
• emergency O2 store

Question 14

Why do mice have an oxygen dissociation curve shifted down?

Answer 14

• large surface area to volume ratio so lots of heat loss
• need a high metabolic rate to generate more heat
• tissues have a high demand for O2

Question 15

What 2 ways can carbon dioxide get carried out of the body?

Answer 15

1) as carbamino haemoglobin

2) as hydrogen carbonate ions

Question 16

How does a carbamino haemoglobin from?

Answer 16

Carbon dioxide covalently binds to amino groups in the haemoglobin polypeptide chain

Question 17

How does the majority of carbon dioxide waste leave the body?

Answer 17

As hydrogen carbonate ions

Question 18

How are hydrogen carbonate ions formed?

Answer 18

Carbon dioxide reacts with water to form carbonic acid, which dissociates into carbonate ions and H+

Question 19

How have red blood cells adapted to get rid of CO2

Answer 19

Red blood cells contain the carbonic anhydrase enzyme which speeds up the reaction of CO2 -> Hydrogen carbonate ions