4.3.3 - Transporting carbon dioxide and oxygen

Question 1

Describe the structure of haemoglobin.

Answer 1

Made up of 4 polypeptide chains each with a haem group.
2 Alpha glucose chains. 2 Beta glucose chains.

Question 2

What is haemoglobin known as when it’s oxygenated?

Answer 2

Oxyhaemoglobin

Question 3

Role of haemoglobin.

Answer 3

Readily associates with oxygen in the lungs.
Readily dissociates with oxygen at respiring tissues.

Question 4

Why is it easier for oxygen molecules to associate with haemoglobin after the first one is loaded?

Answer 4

The haemoglobin changes shape.

Question 5

Why does it become more difficult for the 4th oxygen molecule to load?

Answer 5

Less chance - only one more oxygen molecule can load onto that haemoglobin molecule.

Question 6

Where does the loading and unloading of oxygen occur?

Answer 6

Loading - The lungs
Unloading - Respiring tissues

Question 7

What is the affinity of haemoglobin?

Answer 7

The chemical attraction of haemoglobin towards oxygen.

Question 8

What does a high affinity of haemoglobin mean?

Answer 8

Takes up oxygen easily, releases less easily.

Question 9

What is partial pressure?

Answer 9

The pressure exerted by a gas (the concentration)

Question 10

In the graph showing the relationship between saturation of haemoglobin with oxygen and pp, why is the graph shallow at first?

Answer 10

The shape of haemoglobin makes it difficult for oxygen to load.

Question 11

In the graph showing the relationship between saturation of haemoglobin with oxygen and pp, why does the graph get steeper in the middle?

Answer 11

The haemoglobin molecule changes shape after the first oxygen molecule binds making it easier for other oxygen molecules to bind.

Question 12

In the graph showing the relationship between saturation of haemoglobin with oxygen and pp, why does the graph plateau?

Answer 12

Most binding sites are occupied so more unlikely for an oxygen molecule to find an empty binding site.

Question 13

Describe how oxygen is transported, loaded and unloaded in the blood.

Answer 13

Haemoglobin carries oxygen
In red blood cells
Loading of O2 takes place in lungs
At a high PO2
Unloads at respiring tissues
At a low PO2
Unload at a higher C02 concentration.

Question 14

What does a further left curve mean?

Answer 14

A greater affinity of haemoglobin for oxygen.

Question 15

What happens to the affinity of haemoglobin for oxygen at high PCO2?

Answer 15

It is reduced, enables more oxygen to be unloaded at respiring tissues.

Question 16

Which way will the graph shift if carbon dioxide concentration is increased?

Answer 16

Shift right.

Question 17

What is the Bohr effect?

Answer 17

The greater the concentration of carbon dioxide, the more readily haemoglobin unloads oxygen.

Question 18

Features of fetal haemoglobin.

Answer 18

Higher affinity for oxygen at the same PO2 as adult Hb.
Loads at a PO2 which adult Hb deloads.

Question 19

Features of myglobin

Answer 19

Higher affinity for O2 than fetal Hb
Stores O2 in muscle
Only unloads when oxygen concentration is very low.
Found in human muscles.

Question 20

Is the fetal Hb curve to the left or right of the adult Hb curve?

Answer 20

Left - greater affinity

Question 21

Is the myoglobin curve to the left or right of the adult Hb curve?

Answer 21

Left