protein function - o2 transport Flashcards
what is myoglobin
a much smaller molecule responsible for transporting oxygen in the tissues.
why do we need oxygen transporters in the body?
diffusion alone is not enough and 02 Is non polar which means it doesn’t dissolve in solution meaning it requires a carrier molecule.
structure of a heam group
protoporphyrin ring with an FE group in the centre. The structure can make 2 additional bonds either side of the plane
how does the haem group bind oxygen
1 molecule of o2 binds to the haem group to the Fe. The Fe also binds a histadide/histadine residue on the other side of the plane. The binding of o2 does the Fe group up into the centre of the plane. Histadine moves with it.
why does myoglobin create a hyperbola curve and haemoglobin create a sigmoidal curve
this is because in haemoglobin there are 4 haem units meaning it can bind to 4 o2 molecules. This means that each time an o2 binds the structure of haemoglobin changes. Each time there is a larger surface area for oxygen to bind meaning the affinity for oxygen increases each time.
what is the T state and the R state?
T state= lower affinity
R state= higher affinity (larger surface area for o2 to come in and bind)
what is cooperative binding?
when the first o2 binds there is l ow affinity for oxygen but this creates a higher affinity for the binding of the second o2. This means o2 can be picked up in the lungs much more efficiently
how does 2,3-bisphosphogylserase regulate o2 binding?
2,3-bpg lowers the affinity of haem for oxygen. It does this by holding the haem molecule more tightly together with electrostatic interactions. converts it back to T state.
when is 2,3-BPG released
BPG conc increases at high altitudes so that less o2 is picked up in lungs. This is why you get shortness of breath. However still the same amount is transported it means that more is released to the tissues.
explain the Bohr effect
Binding of H+ and CO2 also lowers the affinity of hb for o2. This is important because then when oxygen reaches respiring tissue it is released to supply o2 to tissues
what is carbon monoxide poisoning
CO binds haemoglobin 250x more strongly than o2 and therefore blocks oxygen transport. This can be fatal.
How to cure CO poisoning?
use hyperbaric chambers to increase the po2 in the lungs and remove the CO
fetal vs adult haemoglobin
fetal haem has different glib genes which are only switched o the a foetus. It has higher affinity for oxygen than adult haem which is important so the baby can get o2 from its mother.
sickle cell anaemia
mutation; glutamate(hydrophil) -> valine(hydropho) and therefore a hydrophobic pocket is formed. Less o2 picked up. Half moon structure. rigid and more likely to lyse.
thalassaemia
genetic disorder where there is an imbalance between beta and alpha chains in haemoglobin.
