Haemoglobin Flashcards
(25 cards)
What unit does haemoglobin and haemocyanin have
Haemoglobin - haem unit (iron)
Haemocyanin - copper unit
What does haemoglobin do? How
Haemoglobin transports oxygen by combining with it
An Fe2+ ion (haem group) binds with one O2 molecule
Structure of haemoglobin
Made up of 4 polypeptide chains
Each polypeptide chain is associated with a haem group
A haem group is an iron (Fe2+) ion
How many O2 molecules can be carried by a haemoglobin molecule
4
What is the role of haemoglobin? What must it do to be efficient
It must readily associate with oxygen at the surface where gas exchange takes place and dissociate from oxygen at the tissues which require the oxygen
Where does loading occur? What is it
Loading occurs at the lungs
Haemoglobin readily associates with oxygen
Where does unloading occur? What is it
The respiring tissues
Where oxygen readily disassociates from haemoglobin
Why is it hard for the first oxygen molecule to bind to haemoglobin? What happens after this
Because the first oxygen has change the shape of the haemoglobin before it binds to it
After the conformational change it becomes much easier for the oxygens to bind to the haemoglobin during loading
What is the unit for partial pressure of oxygen and for carbon dioxide? What is it measured in
pO2 and pCO2
Measured in kilopascals (kPa)
What is the pO2 of inhaled air in the alveoli and the pO2 of active tissues
Alveoli - 14 kPa
Active tissues - 2.7 kPa
What happens at the start of the loading association curve
The graph is steep
1st molecule of oxygen combines with the haem group and distorts it slightly
The joining of the 1st oxygen is slow
What happens in the middle of the loading association curve
The curve begins to speed up
After the haem groups quaternary and tertiary structure changes shape the other 3 oxygen molecules can bind much more easily making it quicker
What happens at the end of the loading association curve
The curve flattens off
This is because the haem group is almost saturated
Define affinity
The ability of haemoglobin to bind with oxygen
Define loading/associating
The process by which haemoglobin binds with oxygen
Define unloading/disassociating
The process by which haemoglobin releases oxygen
What is the affinity for oxygen like when CO2 is present? Why
The affinity for oxygen is reduced in the presence of carbon dioxide
This is because CO2 is acidic so it will change the tertiary structure of haemoglobin by breaking ionic bonds, making it to release oxygen as it binds more loosely
The greater the concentration of CO2 the more readily the haemoglobin releases oxygen and the lower the affinity
How does the affinity for oxygen differ in the lungs and respiring tissues because of the partial pressure of CO2
Lungs have a low CO2 concentration, so the affinity of haemoglobin for oxygen is increased. Oxygen is readily loaded by haemoglobin, so the oxygen disassociation curve shifts to the left
In the respiring tissues there is a higher amount of CO2 so the curve shifts to the right and the affinity for oxygen is lowered
Why does the curve shift to the right when there is more CO2 in the tissues
Because CO2 reduces the pH, changing the shape of the haemoglobin as it denatures. This makes it harder to bind to the oxygen making the affinity lower
Define high affinity
Takes up oxygen more easily, releases it less readily
Define low affinity
Takes up oxygen less easily, releases it more readily
What happens the further to the left the curve goes?
The further to the left, the greater the affinity for oxygen so the more easily it takes up oxygen and the less easily it releases it (holds on to it)
What happens the further to the right the curve goes?
The further to the right, the lower the affinity for oxygen so the less easily it takes up oxygen and the more easily it releases it (doesn’t hold on to it)
When is important to have a high affinity for oxygen? Why
In lower oxygen environments
So they can hold on to the little oxygen available for as long as possible
