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Oxygen transport
Haemoglobin, Myoglobin, Buffering systems
Question | Answer |
---|---|
State the Henderson Hasselbalch equation | pH = pKa + (log[A-]/[HA]) |
Describe the haem molecule | Porphyrin molecule to which an iron atom (Fe2+) is coordinated; the porphyrin ring is a complex C-N structure |
How is haem attached to globin and what does this do? | Attached to the globin chain through proximal histidine residue prevents oxidation of iron to higher oxidation states |
Why is haem protected by the globin polypeptide? | Minimises spontaneous oxidation of Fe2+ to Fe 3+ |
How does O2 binding change the shape of haemoglobin? | Heme assumes a planar configuration and the central iron atom occupies a space in the plane o the heme group |
Describe the shape of deoxygenated heme | Heme is domed: iron atom in the center is drawn out of the plane |
How does the O2 binding change the shape of deoxyhaemoglobin? | Binding of O2 causes conformational changes which lead to breakage of some of the non-covalent interactions between subunits |
Describe the co-operative binding of O2 to Hb | Each subunit of Hb binds O2 independently, the binding of O2 at one subunit influences the binding of O2 at other subunits |
How does 2,3 BPG stabilise the tense state of haemoglobin? | Binds in the cleft between subunits only present in the T-state |
Describe the oxygen binding characteristics of myoglobin | Myoglobin consists of alpha helices containing haem bound to two histidine residues which are involved in oxygen binding |
Describe the oxygen binding characteristics of haemoglobin | Haemoglobin is a tetramer with only one histidine residue involved when oxygen binds to haem. There are four haemoglobin molecules |