Lecture 5 Flashcards
What is the normal position of Fe2+ in a deoxygenated haem group? What happens when the haem becomes oxygenated?
in the deoxygenated form it is slightly pushed out (0.6 angstrom from the plane of the porphyrin ring, when oxygen binds it draws the His F8 down, in turn causing the F helix to reposition and leading to a conformation change in each of the haemoglobin subunits.
What is 2,3 BPG?
2,3-biphosphoglycerate binds in the middle of deoxy haemoglobin (which has a large enough centre space for it), this makes it less able to bind oxygen. It has a negative charge at physiological pH due to the two phosphate groups and is held in place by four histadine side chains (one from each globin subunit) due to their positive charge at physiological pH.
What happens with and without BPG to the oxygen binding affinity of haemoglobin?
Without it becomes similar to myoglobin (fully saturates and releases at very low partial pressures of oxygen), with BPG a more progressive sigmoidal graph is shown.
What is the Bohr effect?
This refers to the H+ and CO2 concentration both affecting haemoglobins binding affinity for oxygen. Higher concentrations of either will lower the oxygen binding affinity, aiding the release of oxygen in the muscles and other needing tissues. This means pH affects oxygen binding affinity.
What is the partial pressure of oxygen compared to actively metabolising tissues?
High in lungs, low in actively metabolising tissues.
What is the equilibrium reaction reached in the blood involving CO2? What does this act as?
CO2 + H2O HCO3- + H+.
What happens to the oxygen from haemoglobin once it reaches the muscles if the muscles don’t immediately need the oxygen?
The oxygen gets transfered to myoglobin.
