Transport of oxygen
- Created by: elen roberts
- Created on: 22-05-13 18:15
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- Transport of oxygen
- Heamoglobin
- Quaternary structure, consists of 4 polypeptide chains with a heam group at the centre of each chain
- Each heam group contains an iron atom, one O2 binds to each iron
- Can bind with 4 O2 molecules
- 4 binding steps. Each time O2 is added, H+ is removed to produce Hb(O2)4
- Oxygen dissociation curve
- S shaped
- 4 stages
- 1: high O2 concentration in lungs, so O2 binds, haem becomes 100% saturated.
- 2: In muscle, liver & brain, O2 is used for respiration so concentrations low so haem is only 50% saturated as it unloads half to the cells
- 3: In tissues respiring quickly (contracting muscles) PO2 drops further so saturation is only at around 10% almost 90% is unloaded
- 4: respiring tissue also produce CO2 which dissolves in tissue fluid, lowering the pH, which reduces saturation, (shown by dotted line) the Bohr effect. Saturation is at around 5%, so 95% of O2 is unloaded to respiring tissue
- Different haemoglobins
- Fetus
- Higher affinity for O2 at low PO2, curve is shifted up
- Different ahem allows O2 to diffuse from the mothers blood to the fetes into fettle tissue
- Lugworm
- Live in the mud where the O2 concentration can fall very low as it respires
- Very high affinity for O2 so the curve is shifted ups they can obtain O2 when PO2 is very low
- Mouse
- Lose heat very quickly due to large SA:Vol. ratio so they have a high metabolic rate to generate more heat
- Higher demand for O2, so the curve is shifted down so plenty of O2 is consistently unloaded
- Fetus
- Heamoglobin
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