Haemoglobin Flashcards
What are the haemoglobins?
These are a group of chemically similar molecules found in a wide variety of organisms.
What type of protein structure does haemoglobin have?
It has quaternary structure.
What has the structure evolved to be efficient at?
Unloading oxygen in one set of conditions and loading it in a different set of conditions.
What is the structure of haemoglobin made up of?
Primary, secondary, tertiary, quaternary structure
What is the primary structure of haemoglobin?
This is a sequence of amino acids in the four polypeptide chains.
What is the secondary structure of haemoglobin?
This is what each of these polypeptide chains is coiled into a helix.
Explain the tertiary structure of haemoglobin.
This is where each polypeptide chain is folded into a precise shape, this is an important factor in its ability to carry oxygen.
Explain the quarternary structure of haemoglobin.
This is where all four polypeptides are linked together to form an almost spherical molecule. Each polypeptide is associated with a haem group.
What does each haem group contain?
A ferrous Fe2+ ion
What can each Fe2+ ion bind to?
A single oxygen molecule.
How many O2 molecules can be carried by a single haemoglobin molecule in humans?
4
What is the name in which haemoglobin binds with oxygen?
Loading or associating
Where does loading or associating take place in humans?
In the lungs.
What is the process by which a haemoglobin releases its oxygen called?
Unloading or dissociating
What is meant by high affinity?
The haemoglobin takes oxygen more easily but releases it less easily.
What is meant by low-affinity?
The haemoglobin takes oxygen less easily but releases it more easily.
Why is haemoglobin efficient at transporting oxygen?
It can readily associate with oxygen at the surface where gas exchange takes place;
It can readily dissociate from oxygen at those tissues requiring it.
Can haemoglobin change its affinity?
Yes it can depending on the conditions.
How does a haemoglobin change its affinity?
The shape changes in the presence of certain substances, such as carbon dioxide. In the presence of carbon dioxide, the new shape of the haemoglobin molecule binds more easily to oxygen so it releases its oxygen.
What is affinity?
Chemical attraction
What happens at the gas exchange surface where the oxygen concentration is high and the carbon dioxide concentration is low?
The haemoglobin will have a high affinity for oxygen which will result in the oxygen being associated.
What happens to the affinity of haemoglobin at respiring tissues where oxygen concentration is low but carbon dioxide concentration is high?
The affinity of haemoglobin for oxygen is low and therefore oxygen is dissociated.
What happens at high affinities?
Oxygen is associated.
What happens at low affinities?
Oxygen is dissociated.
