1. Haemoglobin Tissues need oxygen for respiration
4 polypeptides (see protein notes)
Each contains 1 haem group
Each haem group combines with 1 molecule O2
Hb + 4O2 ↔ HbO8

2. Dissociation Curve Hb must pick up & release O2
Put Hb in different partial pressures of O2
Measure amount of O2 retained by Hb
100% is saturated Hb

3. Explanation of Dissociation Curve
In lungs, ppO2 is high
Hb up to 97% saturated with O2
In respiring muscle, ppO2 is low
Hb only 20% saturated
Hb releases up to 80% O2 in respiring tissues
O2 diffuses into tissue for respiration

4. Hb changes shape First O2 combines with Fe in haem group
Alters shape of Hb molecule
Makes it easier for another O2 molecule to combine, then easier again for third
ie dissociation curve rises steeply
Small change in ppO2 causes a large change in amount O2 carried
But Harder for fourth O2 molecule
Curve levels off

5. Effect of CO2 on Hb CO2 produced by respiring cells Diffuses into RBCs
Converted to carbonic acid by carbonic anhydrase:
CO2 + H2O ↔ H2CO3 (H+ + HCO3-)
Haemoglobin combines with H+, forming haemoglobinic acid (HHb)
HHb releases O2

6. Bohr Shift (Bohr Effect)
High ppCO2 causes release of O2
When tissues very active, O2 is required
Dissociation curve shows release of O2 at lower ppO2 due to high ppCO2

7. Hb as a Buffer Mops up H+ from carbonic acid
Otherwise acidic conditions (low pH)
Hb maintains neutral pH

8. Carbon Dioxide Transport
85% as HCO3-
Ions diffuse from RBC into plasma & dissolve
5% as CO2
dissolved in plasma
10% combines with amine groups in Hb
Carbamino-haemoglobin

9. Release of CO2 in Lungs Low ppCO2 in alveoli
CO2 diffuses from plasma into alveoli
CO2 from carbamino-Hb leaves RBC
H+ + HCO3- recombine to form CO2

10. Foetal Haemoglobin
Diffusion of O2 from mothers blood into foetus blood in placenta
Low ppO2 in placenta as foetus is respiring
O2 passes from mother’s blood to foetus
Foetal Hb combines with O2 more readily than mother’s
Higher affinity
‘Rips’ O2 away from mother’s Hb

12. Myoglobin Red pigment, in muscle cells 1 polypeptide; 1 haem group
Combines with 1 O2 molecule
When combined it is very stable
Does not release O2 until ppO2 is very low
At each ppO2, it has higher saturation than Hb

13. Myoglobin as Oxygen Store
Normal respiration levels, Hb releases O2
Myoglobin holds onto some of the O2
Myoglobin can release O2 if use of O2 > supply by Hb

14. Problems with O2 TransportCO
High Altitude

15. CO CO combines strongly with Hb Formed when fuels burn incompletely
Bright red colouration* CO
CO combines strongly with Hb
Formed when fuels burn incompletely
Exhaust fumes, cigarette smoke
CO diffuses from alveoli into RBCs
Readily combines with Haem group in Hb
Forms carboxyhaemoglobin at very low ppCO
CarboxyHb* is very stable; remains in blood
Death by asphyxiation can be caused by 0.1% CO in air

16. Treatment of CO Poisoning
Administer O2 & CO2
O2 replaces CO
CO2 stimulates breathing
Note:
Cigarette smoke contains up to 5% CO
Approx 5% Hb in smokers is permanently combined with CO
Reduces O2 carrying capacity

17. High Altitude At sea level ppO2 = 20kPa
In alveoli ppO2 = 13kPa
Hb almost saturated with O2 (see graph)
At 6500m (21000ft) ppO2 = 10kPa
Alveoli ppO2 = 5kPa
Hb would only be 70% saturated
Altitude sickness
Increase rate & depth of breathing
Dizziness, weakness
Go down!

18. Acute Altitude Sickness
Arterioles in brain dilate
Increases blood flow in capillaries
Fluid leaks into brain tissue
Disorientation
Fluid leaks into lungs
May be fatal
Go down / take O2

19. Acclimatisation Body can adapt, especially up to 5000m
1979 climbers topped Everest without O2
Suffered hallucinations
Number of RBCs increases over 3 weeks
Normally 50% of blood
Up to 70% after acclimatisation

20. Permanent High Altitude
Natives in Andes or Himalayas
Not genetically different
Environmental adaptations
Broader chests
larger lung capacity
Larger heart
especially the right side which pumps to lungs
More Hb in blood
more efficient O2 transport