Haemoglobin Flashcards
Why can’t oxygen be carried in the blood as it is
Solubility of oxygen in aqueous solutions is low
More efficient to have the oxygen-carrying molecule haemoglobin
How many molecules of haemoglobin does an erythrocyte carry
300 million
Haemoglobin
A quaternary protein Composed of four subunits Each containing a haem group (Fe2+) Has an affinity for oxygen Carries oxygen in the blood
Affinity
Chemical attraction
What is formed when oxygen and haemoglobin combine
Oxyhaemoglobin
Percentage saturation of haemoglobin
Oxygenated haemoglobin/Maximum saturation x 100
Partial pressure of oxygen
The amount of oxygen in a mixture of gas or solution
pO2/kPa
Lower pO2
Less haemoglobin saturated with oxygen
Where is the low partial pressure of oxygen
Tissues/respiring cells
Around 5kPa at rest
Where is the high partial pressure of oxygen
In lungs
Around 16kPa
In capillaries around 13.16kPa
Loading/association
When oxygen is taken up by haemoglobin
Unloading/dissociation
When oxygen is released/given up by haemoglobin
When is oxygen unloaded
In low oxygen concentrations
Low pO2/kPa
So it can be used by respiring cells/tissues
When does Hb have a higher affinity for oxygen
At high partial pressures of oxygen
Explain the cooperative nature of oxygen loading
The first oxygen molecule binding to Hb alters its three D tertiary structure
Exposing the 2nd and 3rd binding sites
So it is easier for the 2nd and 3rd oxygen molecules to bind and load
Oxygen dissociation curve name of shape
Sigmoid
Hb maximum saturation
98%
When red blood cells pass through the pulmonary capillaries
Explain the importance of the pO2 in tissues
Low due to aerobic respiration
Hb has a lower affinity for O2 at lower pO2 so oxyhaemoglobin starts to break down and oxygen is unloaded
How does the oxygen dissociation curve provide evidence for the cooperative nature of oxygen loading
At low pO2 there is little increase in saturation as oxygen increases
Then a rapid increase as it gets easier for 2nd and 3rd oxygen molecules to bind
Explain the effect of increased respiration on oxygen dissociation
Tissue cells respire anaerobically
Reducing the dissolved oxygen in the surrounding tissue fluid
Reducing partial pressure to a level lower than normal
Oxygenated blood with fully saturated haemoglobin unloads oxygen more readily
Due to Hb now having a lower affinity to oxygen because of low kPa
More oxygen unloaded at respiring cells for respiration to provide ATP for muscle contraction
What is the effect of carbon dioxide in the blood
Dissolves in the blood
Making it more acidic and lowering pH
Since Hb is a protein the change in pH slightly alters its tertiary structure
So it has a lower affinity to O2 at high levels of pCO2
Explain the Bohr shift
Higher than normal pCO2 causes oxygen dissociation curve to shift to the right
CO2 makes blood more acidic so changes the shape of the protein Hb
Reducing its affinity to oxygen
And decreasing the saturation for the same pO2
Since the pO2 will be high at respiring cells, more oxygen will be unloaded
To be used for aerobic respiration to produce ATP
To meet the demands of oxygen of the organisms cells
Explain the relationship between surface area to volume ratio of mammals and the effect of this on the oxygen dissociation curve of their Hb
Smaller mammals have a greater surface area to volume ratio
So more more heat lost per unit mass
Smaller mammals have a greater rate of respiration/metabolism
Oxygen is required for this aerobic respiration
So Hb unloads oxygen more readily at the tissues because has a lower affinity for oxygen
Shifts to right
What does a steep oxygen dissociation curve mean
Oxygen unloaded more readily in small decreases of oxygen
Advantage of the oxygen dissociation curve of a foetus being to the left of its mother
Higher affinity so loads more oxygen
At low partial pressures of oxygen
Oxygen can move from the mother to the foetus
Explain lugworm haemoglobin
Live in burrows in sand, water fills up hole when tide changes
Use oxygen that diffuses into it from surrounding water
Hb will have a higher affinity for oxygen
So can saturate Hb at low partial pressures
Since between tides the pO2 will be low
Tissues still have a slightly lower pO2
Steep curve means oxygen will be unloaded rapidly at tissues when required even when only small changes in pO2
Explain how oxygen is loaded and transported and unloaded in the blood
Hb has a high affinity for oxygen
Carries oxygen as oxyhaemoglobin in the red blood cells
Association/loading occurs in the lungs
At high partial pressures of oxygen
Unloaded/dissociation occurs at respiring tissues
At low partial pressures of oxygen
Caused by a higher concentration of carbon dioxide and a reduced affinity
Explain the relationship between Foetal and Adult haemoglobin
Different tertiary structure
Foetal has a higher affinity for oxygen at low partial pressures of oxygen
Like those in the womb
Meaning oxygen can still get to the foetus even if there is little oxygen left in the mothers blood
Once born foetal Hb breaks down in the first few months
And is replaced by adult Hb
Which has a decreased affinity for oxygen
So more oxygen is unloaded at the respiring cells/tissue
So more aerobic respiration to produce the energy in the form of ATP needed for things like growth and movement
