Topic 3---B: More Exchange and Transport Systems- 2. Haemoglobin

Question 1

What is the role of haemoglobin?

Answer 1

• Carry oxygen around the body

Question 2

What is haemoglobin?

Answer 2

• It’s a large protein with a quaternary structure
• It’s made up of 4 polypeptide chains
• Each chain has a haem group which contains an iron ion
• In the lungs, oxygen joins to haemoglobin in red blood cells to form oxyhaemoglobin

Question 3

What is association?

Answer 3

When an oxygen molecule joins to haemoglobin

Question 4

What is dissociation?

Answer 4

When oxygen detatches from oxyhaemoglobin

Question 5

What is affinity for oxygen?

Answer 5

The ability of haemoglobin to attract or bind to oxygen

Question 6

What does haemoglobins affinity for oxygen depend on?

Answer 6

The partial pressure of oxygen

Question 7

What happens when partial pressure of oxygen increases?

Answer 7

Haemoglobins affinity for oxygen increases
so oxygen loads onto haemoglobin where there is a high partial pressure of oxygen to form oxyhaemoglobin

Question 8

What happens when there is a lower partial pressure of oxygen?

Answer 8

Oxyhaemoglobin unloads it’s oxygen

Question 9

Alveoli in lungs

Answer 9

• They have a high partial pressure of oxygen
• Oxygen loads onto haemoglobin to form oxyhaemoglobin
• High affinity
• High oxygen concentration
• saturation of oxygen is high

Question 10

What happens when cells respire?

Answer 10

• They use up oxygen which lowers the partial pressure of oxygen
• Low affinity
• Oxygen unloads
• Low oxygen concentration

Question 11

Respiring tissue

Answer 11

• low oxygen concentration
• Low partial pressure of oxygen
• Oxygen unloads
• Low affinity
• saturation of oxygen is low

Question 12

Dissociation curve

Answer 12

• Shows how saturated the haemoglobin is with oxygen at any given partial pressure
• When partial pressure is high, haemoglobin has a high affinity for oxygen so it has a high saturation of oxygen
• When partial pressure is low, haemoglobin has a low affinity for oxygen so it has a low saturation of oxygen.

Question 13

Describe the role of red blood cells and haemoglobin in oxygen transport

Answer 13

• red blood cells contain lots of haemoglobin as they have:
• no nucleus
• high sa:v
• biconcave
• short diffusion path
• haemoglobin associates with oxygen at gas exchange surfaces where partial pressure of oxygen is high
• This forms oxyhaemoglobin which transports oxygen
• Haemoglobin dissociates from oxygen where partial pressure is low

Question 14

Explain how the cooperative nature of oxygen binding results in an s-shaped (sigmoid) oxyhaemoglobin dissociation curve

Answer 14

• Binding of first oxygen changes the quaternary structure of haemoglobin
• This uncovers the haem group binding sites making further binding of oxygen easier.
• But as the haemoglobin starts to become saturated it gets harder for more oxygen molecules to join
• The curve has a steep bit in the middle where it’s really easy for oxygen to join but shallow bits at each end where its harder for it to join. (when haemoglobin starts to get saturated).

Question 15

What is the partial pressure of carbon dioxide a measure of?

Answer 15

The concentration of carbon dioxide within a cell

Question 16

When does haemoglobin give oxygen up more readily?

Answer 16

At a higher pCO2

Question 17

What raises the PCO2?

Answer 17

• When cells respire as they produce carbon dioxide which raises the PCO2.
• This increases the rate of oxygen unloading (rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen)
• The dissociation curve shifts to the right but it stays the same shape

Question 18

What is the bohr effect?

Answer 18

High carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right and affinity for oxygen decreases as acidic carbon dioxide changes the shape of the haemoglobin slightly.

Question 19

What does it mean when the disscoiation curve is more to the left?

Answer 19

The higher the haemoglobins affinity for oxygen

Question 20

Explain effect of Co2 concentration on the dissociation of oxyhaemoglobin?

Answer 20

• Increasing blood Co2 (increased rate of repsiration)
• Lowers blood pH (acidic)
• Reducing haemoglobins affinity for oxygen as the quaternary structure changes slightly
• So faster unloading of oxygen to respiring cells

Question 21

Explain the advantage of the Bohr effect during exercise?

Answer 21

• More dissociation of oxygen so faster aerobic respiration so more ATP produced.

Question 22

What type of haemoglobin would you have for low oxygen environments?

Answer 22

• Haemoglobin with a higher affinity for oxygen than human haemoglobin.
• As there isn’t much oxygen available so the haemoglobin has to be very good at loading available oxygen.
• The dissociation curve of the haemoglobin is to the left

Question 23

What type of haemoglobin would you have for high activity levels?

Answer 23

• Haemoglobin with a lower affinity for oxygen than human haemoglobin as organisms that are active need their haemoglobin to easily unload oxygen so it’s available for them to use.
• The dissociation curve of the haemoglobin is to the right of the human one

Question 24

What type of haemoglobin would you have if you were a small mammal and lose heat quickly with a high metabolic rate?

Answer 24

• Haemoglobin with a lower affinity for oxygen than human haemoglobin because they need their haemoglobin to easily unload oxygen to meet their high oxygen demand.
• The dissociation curve of their haemoglobin is to the right of the human one.