Haemoglobin

Question 1

What are haemoglobins?

Answer 1

They are protein molecules with a quaternary structure which is efficient for loading oxygen in one condition and unloading it under a different condition.

Question 2

What are the structures of haemoglobin?

Answer 2

1) Primary structure - a sequence of amino acids in 4 polypeptide chains.
2) Secondary structure - each of those polypeptide chains is coiled up into helix.
3) Tertiary structure - Polypeptide chains are folded into specific shapes which is important for its ability to carry oxygen.
4) Quaternary structure - All 4 polypeptide chains are linked together into a spherical shape. Each polypeptide is associated with a haem group which contains Fe2+ ions. Each Fe2+ ion can combine with a single oxygen molecule hence every single haemoglobin can carry up to 4 O2 molecules.

Question 3

What is the process by which haemoglobin binds with oxygen?

Answer 3

Associating - In human it takes place in the lungs.

Question 4

What is the process by which haemoglobin releases its oxygen?

Answer 4

Dissociating - In human it takes place in the tissues.

Question 5

What’s the difference between haemoglobins which has a high affinity for oxygens and haemoglobins with low affinity?
Affinity - How much they like oxygens.

Answer 5

High affinity would allow the oxygens to be taken up more easily but it’s hard to release them.
Low affinity means that it’s harder to pick up the oxygens but it’s easier to release them.

Question 6

What is the role of haemoglobin?

Answer 6

To transport oxygen.

Question 7

How can haemoglobins be efficient at oxygen transportation?

Answer 7

• Readily associated with oxygen at the surface where gas exchange takes place.
• Readily associated with oxygen at those tissues who requires it.
  Those conditions change its affinity for oxygen under different conditions.

Question 8

How can haemoglobin change its affinity for oxygen under different conditions?

Answer 8

It changes shape due to the presence of certain substances e.g. CO2, in the presence of CO2, the new shape of the haemoglobin molecule will bind more loosely to oxygen, therefore, it releases its oxygen.

Question 9

Describe the affnity for oxygen under different conditions.

Answer 9

• Gas exchange surface:
• O2 concentration - High
• CO2 concentration - Low
• Affinity of haemoglobin for oxygen - High
• Result - O2 is associated
• Respiring tissues:
• O2 concentration - Low
• CO2 concentration - High
• Affinity of haemoglobin for oxygen - Low
• Result - O2 is dissociated

Question 10

How did scientists find out that organisms were possessed with haemoglobin and why is there different types of haemoglobin?

Answer 10

It carried oxygen from the gas exchange surface to the tissue which required it for respiration so it means that it must be readily combined with O2 in the first place.
They also investigated that there’s different abilities of haemoglobin that combined with O2 and their different properties depended upon the way they took up and released oxygen.

Question 11

Why do different haemoglobin have different affinities for oxygen?

Answer 11

It depends on the shape of the molecule because each species produces a haemoglobin which has different sequence of amino acid so they would all have different tertiary and quaternary structure so it ranges them from having high affinity and low affinity for oxygen.