CSI 2 Flashcards
What are harm groups made of
Porphyrin ring bound to a ferrous iron ion (Fe2+)
What does oxygen bind to in the harm groups?
The Fe2+ ion
How many functional globin chains are there
8
What are the functional globin chains?
Alpha 1, Alpha 2, Beta, A Gamma, G Gamma, Delta, Epsilon, Zeta
What is the alpha globin cluster made of?
5’ zeta, alpha 2, alpha 1 3’
What is the beta globin cluster made of?
5’ epsilon, G gamma, A gamma, delta, beta 3’
Which globin chains make up HbA?
2 alpha and 2 beta
Which globin chains make up HbA2?
2 alpha and 2 delta
Which globin chains make up fetal haemoglobin?
2 alpha and 2 gamma
What does P50 mean
The value at which 50% of the harm groups have oxygen bound
What is the P50 of myoglobin?
2 torr
What is the P50 of haemoglobin?
26 torr
What is fractional saturation?
The fraction of haem groups that have oxygen bound
What curve is for haemoglobin?
Sigmoidal oxygen dissociation curve
Where is myoglobin found?
Muscles
What is ppO2 in the lungs like?
100 torr -> haemoglobin becomes highly saturated with oxygen
What is the ppO2 in the tissues like?
20 torr -> Haemoglobin releases around 66% of its oxygen
What is positive cooperativity?
Once an oxygen molecule binds to one haem group, it becomes easier for oxygen to bind to the next haem group within the molecule
What is 2,3-BPG?
It’s an allosteric effector that binds to a site in deoxyhaemoglobin and stabilises the structure
What is the effect of 2,3-BPG?
It decreases the affinity of haemoglobin for oxygen. This shifts the curve to the right. This is what allows the haemoglobin to act as an effective oxygen carrier.
Haemoglobin in the absence of 2,3-BGP does not have the sigmoidal shaped oxygen dissociation curve
How is 2,3-BGP generated?
Through the Rapoport-Leubering Shuttle
In the shuttle, some of the 1,3-BGP produced in glycolysis is converted into 2,3-BPG by movement of a phosphate group.
Which enzyme catalyses formation of 2,3-BPG?
Bisphosphoglycerate mutase (BPGM)
What happens in rapidly respiring cells?
Pyruvate is decarboxylated to acetyl coA forming CO2
Pyruvate is converted to lactate so pH decreases
How does pH and CO2 affect haemoglobin?
H+ ions and CO2 are allosteric effectors which bind to sites in haemoglobin and decrease the affinity for oxygen so oxygen is released when RBCs enter the tissues
How does age affect globin gene expression?
A foetus would produce more alpha and gamma goblins.
After birth, there is more production of beta goblins and less production of gamma globins.
A very small amount of HbF persists throughout adult life.
Other than sickling, what can be seen in the blood of people with SCA
More HbF than people without SCA to compensate