Haemoglobin

Question 1

What is haemoglobin?

Answer 1

A large protein with a quaternary structure: it is 4 polypeptide chains and 4 iron ion prosthetic groups which travels in blood to carry oxygen

Question 2

Structure of haemoglobin

Answer 2

4 polypeptide chains
2 alpha glob in 2 beta globin
4 iron haem groups

Question 3

Where does oxygen bind to in haemoglobin?

Answer 3

4 iron prosthetic groups

Question 4

Loading and unloading of oxygen to haemoglobin

Answer 4

Haemoglobin + 4 oxygen to form oxy haemoglobin
A reversible reaction so oxy haemoglobin can unload all 4 oxygen

Question 5

Loading

Answer 5

Oxygen binds to iron in haemoglobin

Question 6

Unloading

Answer 6

Oxygen unbinds from oxyhaemoglobin

Question 7

What does the loading of oxygen onto haemoglobin depend upon?

Answer 7

The affinity haemoglobin has for oxygen

Question 8

What affects the affinity haemoglobin has to oxygen?

Answer 8

The partial pressure of oxygen in the area

Question 9

Trend for oxygen loading onto haemoglobin

Answer 9

Where there is a high partial pressure for oxygen, oxygen will unload onto haemoglobin more so higher affinity
So haemoglobin has a high % saturation to oxygen

Question 10

Where does oxygen mostly load onto haemoglobin?

Answer 10

In the alveoli in the lungs because a high partial pressure of oxygen
Oxygen diffuses into blood from alveoli into blood

Question 11

Trend for oxygen unloading from haemoglobin

Answer 11

Where there is a low partial pressure for oxygen, oxygen will unload from haemoglobin
So less affinity
And lower % saturation of haemoglobin with oxygen

Question 12

Where does oxygen unload from haemoglobin?

Answer 12

In respiring tissues where oxygen has been used in respiration so has a low partial pressure of oxygen into cells

Question 12

Affinity for oxygen in lungs

Answer 12

High

Question 13

Affinity for oxygen in respiring tissues

Answer 13

Low

Question 14

Partial pressure of oxygen

Answer 14

A measure of oxygen concentration in a given volume caused by oxygen molecules colliding which exerts pressure

Question 15

Dissociation curve

Answer 15

Shows the % saturation of haemoglobin with oxygen on y axis
Partial pressure of oxygen on x axis
Thus overall affinity oxygen has to haemoglobin at various pO2

Question 16

Shape of a dissociation curve

Answer 16

S shaped

Question 17

Why is the dissociation curve or haemoglobin not linear but S shaped?

Answer 17

Due to the structure of haemoglobin and the 4 binding sites of oxygen: as more oxygen binds, tithe affinity for oxygen decreases

Question 18

Steep S shaped part of dissociation curve ?

Answer 18

When 1 oxygen binds to a haem group, the shape of haemoglobin (tertiary structure) alters to make it easier for more O2 to bind BECAUSE OTEHR BINDING SITE IS UNCOVERED
thus for a small increase in pO2, the % saturation increases rapidly

Question 19

Bohr effect

Answer 19

The partial pressure of CO2 increasing in a cell can decrease affinity of oxygen to haemoglobin
Due to increase in acidity of the blood as concentration of CO2 increases

Question 20

Effect of increasing pCO2

Answer 20

Haemoglobin unloads easily
So at a given partial pressure of oxygen, there is a lower % saturation of haemoglobin with oxygen

Question 21

Effect of increasing pCO2 on the graph

Answer 21

Shifts right

Question 22

Effect of decreasing pCO2

Answer 22

There is higher affinity for oxygen so oxygen doesn’t unload from haemoglobin easily

Question 23

Effect of decreasing pCO2 on the graph

Answer 23

Shifts left so for any given pO2, the % saturation haemoglobin has of oxygen is higher (so lower affinity)

Question 24

What factors can affect the type of haemoglobin in an organism (thus affinity for O2)

Answer 24

Oxygen level in environments Activity levels Size

Question 25

Animals which live in environments with low oxygen levels?

Answer 25

Haemoglobin has high affinity for oxygen compared to living in normal pO2 environments So it can bind to any available oxygen so high % saturation for a given pO2

Question 26

Effect on the graph of living in low pO2 environments

Answer 26

Shifts left so for a given partial pressure, higher affinity for oxygen for given pO2

Question 27

Animals with high activity levels?

Answer 27

Have high activity have a higher demand for oxygen thus need a lower affinity for oxygen at a given pO2 so more oxygen unloaded to respiring tissues

Question 28

Effect on the graph of animals with high activity levels

Answer 28

Shifts right for a given partial pressure, the % saturation of oxygen is lower

Question 29

Animals that are smaller effect?

Answer 29

Higher sa:vol ratio so lose heat MORE More metabolic rate to maintain body temp so higher demands for O2 So for a given pO2, the affinity to oxygen is lower

Question 30

Co operative binding of haemoglobin

Answer 30

When 1 oxygen binds to haemoglobin, tertiary structure of haemoglobin alters to uncover second binding site So affinity haemoglobin has to oxygen increases so more oxygen can bind easier