7.1 Mass Transport - Haemoglobin

Question 1

Describe the structure of haemoglobin

Answer 1

Primary structure - Sequence of amino acids in the four polypeptide chains

Secondary structure - In which all of these amino acids are coiled into a helix

Tertiary structure - In which each polypeptide chain is folded into a precise shape - an important factor in its oxygen carrying ability

Quarternary structure - All four polypeptide chains are linked together to form a spherical molecule. Each polypeptide is associated with a haem group, which contains a ferrous group that can combine with an oxygen moilecule

Question 2

What is the loading of oxygen and where does it take place

Answer 2

The process by which oxygen binds with haemoglobin and this occurs in the lungs

Question 3

What is the unloading of oxygen and where does it take place

Answer 3

The process by which haemoglobin releases its oxygen and this occurs at respiring tissues

Question 4

What does ‘high affinity’ mean

Answer 4

A haemoglobin molecule can easily bind with oxygen but release it less easily

Question 5

What features must haemoglobin have to be efficient at transporting oxygen

Answer 5

1. Must be able to easily associate with oxygen at the surface where gas exchange takes place
2. Readily dissociate from oxygen at those tissues requiring it

Question 6

What special property does haemoglobin have

Answer 6

Under different condition it changes its affinity (chemical attraction) for oxygen

Question 7

How does haemoglobin change its affinity for oxygen under different conditions

Answer 7

Its shape changes in the presence of substances like carbon dioxide. The new shape binds more loosely to oxygen, as a result haemoglobin releases its oxygen

Question 8

Why are there different haemoglobins

Answer 8

Each species produces a haemoglobin with a slightly different amino acid sequence. The haemoglobin of each species therefore has different tertiary and quarternary structures and hence different oxygen binding properties