Karteikarten
Haemoglobin
Karten in diesem Stapel (8)
- 1HaemoglobinTetrameric heme, aB heterodimers
Follows sigmoidal curve
Indicates positive co-operativity (affinity changes, first hard, then easier)
Increase pH/decrease CO2, increases Hb O2 affinity and shifts left - 2BPGHigh negative charge
Altitude, low ppO2 so shift curve lower to release more o2
BPG dissolved in blood (bound to Hb), reduces affinity (stabilises T state)
In HbF stabilises R state as less readily available - 3HbA = a2b2HbF = a2y2
- 4Haem stabilised by hydrophobic residues found in interior of protein, protective environment prevents oxidation to Fe3+ (cannot get o2)a and B chain overlap with similar 3D structure, B slightly longer with extra helix, 26.3% sequence identity
- 5Haem binds to helices E and F, these have histidine residues near haem iron. Four coordinates in plane of Hb from porphyrin ring, one co-ordination with F8 (proximal histidine) and one left for O2Distal histidine stabilises O2 bound form and destabilised CO bound form, CO binding 200x stronger
- 6Deoxy HbFe slightly displaced from plane, binding brings it back. Electron transfer Fe2+ -> o2 going to Fe3+ + O- (super oxide). Fe2+ bigger so after o2 iron shrinking, moves up plane. From T state (more contact, histidine protonated - H bonded to Asp, high pKa value. As pH decreases, protonation promotes o2 release so favours T state) to R state (high o2 affinity). Histidine moves vertically (allosteric movement), decreased contact of two chains
- 7Bohr EffectProtons bind to protein sites
CO2 reacts with Hb N-terminal to produce cardamon terminal residues (salt bridges stabilise T state)
In respiring tissues, lower pH, so decreased affinity so o2 released. CO2 + H2O -> HCO3- + H+. HCO3- leaves RBC coupled with Cl-, opposite in lungs - 8ThalassemiaReduced synthesis of a/B chains
Informationen
- Beschreibung
- Karteikarten am Haemoglobin, erstellt von maryamnc am 03/01/2015.
- Erstellt von
- maryamnc
- Aufrufe
- 7
- Bewertung