Haemoglobin

Question 1

What are haemoglobins?

Answer 1

A group of chemically similar molecules found in a wide variety of organisms

Question 2

What is haemoglobin made up of?

Answer 2

4 polypeptide chains (protein) and each polypeptide chain has a haem group attached to it

Question 3

What is a haem group?

Answer 3

A non protein which contains an Fe2+ ion to which one molecule of oxygen binds

Question 4

How many oxygen molecules can one haemoglobin molecule carry?

Answer 4

4

Question 5

What is the primary structure of a haemoglobin molecule?

Answer 5

A sequence of amino acids in the four polypeptide chains

Question 6

What is the secondary structure of a haemoglobin molecule?

Answer 6

Each of the polypeptide chains is coiled into a helix

Question 7

What is the tertiary structure of a haemoglobin molecule?

Answer 7

Each polypeptide chain is folded into a precise shape which is an important factor in its ability to carry oxygen

Question 8

What is the quaternary structure of a haemoglobin molecule?

Answer 8

All 4 polypeptides are linked together to form an almost spherical molecule. Each polypeptide is associated with a haem group

Question 9

What is the process called when haemoglobin binds with oxygen?

Answer 9

Loading / associating

Question 10

Where does loading take place?

Answer 10

lungs

Question 11

What is the process called when haemoglobin releases its oxygen?

Answer 11

Unloading / dissociating

Question 12

Where does unloading take place?

Answer 12

tissues

Question 13

What is loading?

Answer 13

the binding of oxygen to haemoglobin at the gas exchange surface e.g. lungs forming oxygaemoglobin

Question 14

What is unloading?

Answer 14

the release of oxygen from haemoglobin at the tissues

Question 15

What is partial pressure (tension)?

Answer 15

the pressure exerted by a gas if it alone occupied the space

Question 16

When is partial pressure of oxygen the lowest?

Answer 16

During exercise

Question 17

What does haemoglobin do?

Answer 17

-readily binds with oxygen at the surface where gas exchange takes place
-readily dissociates from oxygen at the tissues requiring it

Question 18

Properties of haemoglobin

Answer 18

-changes its affinity for oxygen under different conditions
-has a high affinity for oxygen when the partial pressure of oxygen is high (e.g. the lungs)
-has a low affinity for oxygen when the partial pressure of oxygen is low (e.g. at the tissues)

Question 19

Why are the properties of haemoglobin essential to its function?

Answer 19

As haemoglobin can load large amounts of oxygen as it passes through the lungs and unloads large amounts of oxygen as it passes through the tissues.

Question 20

How does oxygen bind to haemoglobin?

Answer 20

co-operative binding

Question 21

How does increasing carbon dioxide levels affect haemoglobin?

Answer 21

-The production of CO2 causes the formation of carbonic acid, which causes a fall in pH.
-The fall in pH causes a change in the structure of haemoglobin causing it to release its oxygen more readily
-Thus, the more CO2 being produced, the more oxygen being released for respiration

Question 22

What is co-operative binding?

Answer 22

When the haemoglobin molecule binds to the first oxygen molecule it causes a change in its tertiary structure. This reveals more haem groups (binding sites) which makes it easier for the haemoglobin to bind to a second molecule of oxygen, then making it easier for the 3rd and 4th oxygens to bind.

Question 23

How does oxygen dissociate from oxyhaemoglobin?

Answer 23

When oxyhaemoglobin moves into regions of low partial pressure of oxygen (in the tissues) , the 1st oxygen is readily released, but the 2nd, 3rd and 4th are given up successively less readily

Question 24

What is the oxygen haemoglobin dissociation curve?

Answer 24

Shows the percentage saturation of oxygen in haemoglobin when in contact with different partial pressures of oxygen

Question 25

What is the shape of an oxygen dissociation curve?

Answer 25

s-shaped (sigmoidal)

Question 26

Why can the saturation of oxygen in haemoglobin never be 100%?

Answer 26

As it is always being released to cells

Question 27

What is the partial pressure of oxygen in the lungs?

Answer 27

13kPa - 96% saturated, the highest it can be

Question 28

Why is the gradient of the curve initially shallow on an oxygen dissociation curve?

Answer 28

As at low oxygen concentrations, little oxygen binds to haemoglobin.

Question 29

What is significant about the s-shape on an oxygen dissociation curve?

Answer 29

-the steep gradient of the curve shows that large amount oxygen is being given up to the tissues
-As the partial pressure of oxygen in the air in the lungs is about 13 kPa, if we move into a lower oxygen environment (e.g. climb in altitude) the blood remains fully saturated until the partial pressure drops below 9kPa. This allows us to reach nearly 3000 m in height before our blood is no longer saturated at the lungs and we start to feel the effects of altitude

Question 30

What is the Bohr shift?

Answer 30

a rightward shift of the oxygen dissociation curve due to increase in CO2 concentration

Question 31

On an O2 dissociation curve, what does a curve that is closer to the right suggest?

Answer 31

That the haemoglobin has a lower affinity for oxygen, meaning it releases oxygen easier

Question 32

Why is the % saturation of the blood lower after exercise than at rest at x kPa?

Answer 32

As more CO2 is in the blood during exercise, so more oxygen is being released

Question 33

Why do different organisms have different types of haemoglobins?

Answer 33

As animals will adapt to their surroundings and their oxygen requirement

Question 34

Why can haemoglobin be used to compare evolutionary relationships within organisms?

Answer 34

As they are found in many different organisms