HAEMOGLOBIN

- Contained in RED BLOOD CELLS

- Large protein - QUATERNARY STRUCTURE
                         - MADE UP OF 4 POLYPEPTIDE CHAINS

- Each chain - has a 'HAEM' group
- Contain IRON ION - gives red colour

- High affinity for oxygen - can carry four oxygen molecules

- Lungs - oxygen + haemoglobin = oxyhaemoglobin
- REVERSIBLE REACTION

- PARTIAL PRESSURE OF OXYGEN (p02)
- Measure of oxygen concentration
- Greater concentration of dissolved oxygen in cells - HIGHER PARTIAL PRESSURE

- PARTIAL PRESSURE OF CARBON DIOXIDE (pC02)
 - Measure of concentration  inside cell

- Haemoglobin affinity for oxygen - depend on p02
- 02 - load onto haemoglobin - HIGH p02
- Oxyhaemoglobin - unloads oxygen - LOW p02

- 02 - enter blood capillaries at alveoli - from lungs
- Alveoli - high p02 - oxygen load onto haemoglobin - form oxyhaemoglobin

- Cells respire - use up 02 - lowers p02
- Red blood cells - deliver oxyhaemoglobin to respiring cells - unload oxygen

- Show SATURATION OF HAEMOGLOBIN WITH OXYGEN AT ANY PARTIAL PRESSURE

- p02 high - haemoglobin has HIGH AFFINITY FOR 02 - therefore HIGH SATURATION
- p02 low - haemoglobin has LOW AFFINITY FOR 02 - therefore LOW SATURATION - release it

GRAPH - 'S' SHAPED
- First 02 and Hb combine - alter shape to make it easier for other molecules to join
- Hb more saturated - harder for more 02 molecules to join
- Curve is steep in middle - small change in p02 - large change in amount of oxygen carried by Hb

- Hb - give up oxygen MORE READILY - when HIGH pC02

- Cells respire - produce C02 - increase pC02
- Increase rate of oxygen unloading from oxyhaem.
- SHIFT DISSOCIATION CURVE TO THE RIGHT

- Saturation of blood with oxygen - lower for a given pO2
- More oxygen released

- LOW CONC. OF 02 - higher affinity for 02 than human haem. - CURVE TO LEFT OF OURS

- VERY ACTIVE - high oxygen demand - lower affinity for 02 than human haem - CURVE TO RIGHT