INDEPTH: Haemoglobin 3.2.7 Flashcards
What does affinity mean?
The attraction of the haem group to oxygen
what is the name for when oxygen is released from oxyhaemoglobin?
Dissociation
What is the structure of a haemoglobin molecule?
A complex protein worth for subunits.
Each subunit consists of a polypeptide chain and a haem group
The haem group contains a single iron ion (Fe2+)
How many oxygen molecules can a haemoglobin molecule hold?
4
Each haem group can hold one oxygen molecule
Where does association and dissociation of haemoglobin and oxygen occur?
Association
Where the pO2 is high, in the lungs
(high partial pressure of oxygen)
Dissociation
Where the pO2 is low, in the respiring tissues
(low partial pressure of oxygen)
What does the partial pressure of oxygen mean?
The concentration of oxygen
The relative pressure that it contributes to a mixture of gasses
Describe the s - shaped association curve of haemoglobin
At low partial pressures:
- Haem groups are in the centre of the molecule so association with oxygen is harder
- Low saturation of haemoglobin
At Medium partial pressures:
- Oxygen molecule associates, causing conformational change
- Oxygen can bind to the haem group easier
- High saturation
At high partial pressures:
-Saturation levels curve off
How is fetal haemoglobin different from adult?
It has a higher affinity for oxygen
The association curve is to the left of the adult haemoglobin association curve.
Why does fetal haemoglobin need to have a higher association for oxygen than adult?
Because fetal needs to associate with oxygen in the placenta, where the partial pressure of oxygen is low.
The low PP enables oxygen to dissociate from the mothers blood, and then as fetal haem has a higher affinity it can then associate with that oxygen.
This further lowers the PP of the surrounding tissue cause more maternal oxygen to be released.
What the three different options for CO2 once produced via respiration?
1) 5% dissolved directly into the plasma
2) 10% is combined with haemoglobin to form carbaminohaemoglobin
3) 85% is transported in the form of hydrogencarbonate ions
How are hydrogen carbonate ions formed?
1) CO2 diffuses into the red blood cells, combines with water to form a weak carbonic acid
2) This acid then dissociates to release H+ ions and hydrogen carbonate ions
3) Hydrogen carbonate ions diffuse into the blood plasma
How is the charge within the red blood cells maintained once the hydrogencarbonate ions move out?
The Chloride Shift
Chloride ions diffuse into the red blood cell
How is the red blood cell prevented from becoming acidic when carbonic acid dissociates?
Carbonic acid releases H+ ions
Hydrogen ions are taken out of solution by associating with haemoglobin to produce haemoglobinic acid,
The Haemoglobin acts a buffer to maintain a constant pH
What enzyme catalyses the reaction between water and CO2?
Carbonic anhydrase
What is the name of the process by which more oxygen is delivered to the tissues releasing more CO2?
The Bohr effect
