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Haemoglobin
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- 1What is the function of haemoglobin and where is it found?Oxygen-CARRYING protein in RED BLOOD CELLS
- 2Describe the quarternary structure of haemoglobintetramer
alpha2beta2 complex
4 x essential prosthetic groups haem (fe2+) - 3Describe the similarities and differences between the alpha and beta sub-units20% similarity
60% of mutations conserved (mostly hydrophobic a.a.s -> hydrophobic a.a.s)
alpha=141 a.a.s beta=146 a.a.s - 4Describe the 02 saturation curves of myoglobin and haemoglobinMyoglobin = hyperbolic
Haemoglobin = sigmoidal (co-operativity) - 5Explain the mechanism of co-operativity in haemoglobin1) o2 binds to Fe2+
2) Fe2+ moves half a bond length (0.7 A) into plane of ring
3) Pulls His side chain to ring
4) His residue is in F-helix which moves by several A like a lever
5)This breaks interactions allowing rotation of the sub-units - 6What evidence is there that supports co-operativity in haemoglobin during the binding of O2?The sigmoidal response of haemoglobin during the binding of oxygen...
So after 1st oxygen binds allows easier binding of other oxygens due to break in e.s. forces - 7Name the factors that promote the release of oxygen in tissues- H+
- CO2
- BPG (bisphosphoglycerate)
stabilises deoxy form (1 per tetramer) - 8How does does a change in pH effect oxygen release and what is this effect called?Decrease in pH (increase in H+) causes more O2 to be released causing the saturation curve to shift to the RIGHT
This is called the Bohr effect - 9Explain the two ways high CO2 causes the release of oxygen by haemoglobin and write the two related equations1) Generates H+ ions
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
2) Binds directly to Hb amine groups (N-terminus + Lys)
_NH2 + CO2 -> _NH_COO-
prod carbamate ion -> changes charge and 3D structure - 10What is the effect of a lack of BPG on the saturation curve of haemoglobin?LOSE sigmoidal effect
- 11How does BPG stabilise the deoxy form of haemoglobin?BPG is highly negative with 5 negative charges
Tissues are acidic and so both His and Lys are pos. charged
BPG therefore binds at the center of the Hb tetramer stabilising it - 12What is the quarternary structure of foetal haemoglobin?alpha2gamma2
- 13Why does BPG bind less tightly to foetal haemoglobin and why is this important?. Ser143 -> His143
. Serine is not positively charged so BPG binds less tightly
. So O2 binds MORE tightly
. So oxygen can pass from the mother's blood to the foetus - 14How is sickle cell anemia caused?- Defective Hb
- Mutation in beta chain Glu6 -> Val6 so becomes hydrophobic
- No longer soluble so precipitates in RBC - filament distorts RBC
- HBS (homozygous form) is severely impaired - 15Why do many parts of the world have a high incidence of heterozygous individuals with sickle cell anemia?Because heterozygous individuals have an increased resistance to malaria
- 16How can sicle cell anemia be diagnosed chemically?PEPTIDE FINGERPRINTING
to identify mutated amino acid - 17Why can sickle cell anemia cause blockage of the capillaries?RBC can burst due to sickle-cell haemoglobin fibres
This can cause them to get stuck in capillaries
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- (Biochemistry) Biology Fichas sobre Haemoglobin, creado por Charlotte Pedley el 31/12/2017.
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- Charlotte Pedley
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