Mass Transport- Haemoglobin

Question 1

What contains haemoglobin?

Answer 1

Red blood cells

Question 2

What is haemoglobin?

Answer 2

A large protein with a quaternary structure

Question 3

What does each polypeptide chain have?

Answer 3

A haem group which contains an iron ion and gives haemoglobin its red colour

Question 4

How many oxygen molecules can haemoglobin molecules carry?

Answer 4

4 so they have a high affinity for oxygen

Question 5

What happens to haemoglobin in the lungs?

Answer 5

Joins with oxygen to become oxyhaemoglobin

Question 6

What is the partial pressure of oxygen?

Answer 6

Measure of oxygen concentration

Question 7

When is the partial pressure of oxygen higher?

Answer 7

When there is a greater concentration of dissolved oxygen in cells

Question 8

What is the partial pressure of carbon dioxide?

Answer 8

Measure of the concentration of carbon dioxide in a cell

Question 9

What determines how haemoglobin’s affinity for oxygen varies?

Answer 9

The partial pressure of oxygen

Question 10

Where does oxygen load onto haemoglobin to form oxyhaemoglobin?

Answer 10

Where there’s a high partial pressure of oxygen

Question 11

Where does oxyhaemoglobin unload its oxygen?

Answer 11

Where there’s a lower partial pressure of oxygen

Question 12

Where does oxygen enter the lungs?

Answer 12

The blood capillaries at the alveoli that have a high partial pressure of oxygen so oxygen loads onto haemoglobin to form oxyhaemoglobin

Question 13

What happens when cells respire?

Answer 13

They use up oxygen which lowers the partial pressure of oxygen- red blood cells deliver oxyhaemoglobin to respiring tissues where it unloads its oxygen, the haemoglobin then returns to the lungs to pick up more oxygen

Question 14

What does the dissociation curve show?

Answer 14

How saturated the haemoglobin is with oxygen at any given partial pressure

Question 15

What affinity does haemoglobin have at a high partial pressure of oxygen (in the lungs)?

Answer 15

High affinity- readily combine with oxygen so has a high saturation of oxygen

Question 16

What affinity does haemoglobin have at a low partial pressure of oxygen (in respiring tissues)?

Answer 16

Low affinity- releases oxygen rather than combines with it so has a low saturation of oxygen

Question 17

Why is the dissociation curve ‘S-shaped?

Answer 17

When haemoglobin combines with the first oxygen molecule, its shape changes to make it easier for more oxygen molecules to join, but when haemoglobin becomes saturated it gets harder for oxygen molecules to join, curve has steep part in middle where it’s easier for oxygen molecules to join and shallow parts at ends where it’s harder

Question 18

How do partial pressures of carbon dioxide affect haemoglobin’s ability to give up oxygen?

Answer 18

Will give up oxygen more readily at higher partial pressures of carbon dioxide

Question 19

What is the Bohr effect?

Answer 19

• When cells respire, produce carbon dioxide which raises the partial pressure of carbon dioxide
• Increases rate of oxygen unloading so dissociation curve ‘shifts’ right, saturation of blood with oxygen is lower for a given partial pressure of oxygen so more oxygen is being released

Question 20

How is haemoglobin different in different organisms?

Answer 20

• Organisms that live in environments with a low concentration of oxygen have haemoglobin with a higher affinity for oxygen than human haemoglobin- dissociation curve is to the left of ours
• Organisms that are very active and have a high oxygen demand have haemoglobin with a lower affinity for oxygen than humans- dissociation curve is to the right of ourd