Transportation of O2 + CO2
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Describe structure of haemoglobin?
Hb(O2)4 Large globular conjugated protein. 4 subunits ( 2 alpha/2 beta ) Each subunit =1 haem group ~~>each bind to 1 O2 molecule
What does ‘positive co-operativity’ mean?
Binding of 1st O2 changes Hb shape. Steep concentration gradient maintained Increases Hb’s affinity for O2
What does ‘affinity’ mean?
How readily Hb binds to oxygen
What is the oxygen dissociation curve?
Sigmond shape x axis = partial pressure of oxygen y axis = O2 saturation/Hb’s affinity for O2 Oxygen dissociation curves show the affinity of haemoglobin for oxygen.
What does the term ‘partial pressure’ refer to?
Concentration of oxygen within a mixture of gases
What happens at low pO2?
Low affinity -> Little haem group bound with O2
What happens at higher pO2?
Higher affinity More Hb bind to O2 —> becomes more easier to bind to other O2. (positive co-operativity)
What happens at very high pO2?
All haem group bound to O2 Hb = saturated —> becomes oxyhaemoglobin
What is the Bohr effect?
ODC shifts to right —>Hb(O2) releases O2 more readily at high pCO2 areas.
What does Bohr effect mean?
Low pCO2 area = lungs (CO2 removed from RBC into alveoli) —> Hb = higher affinity for O2 .: binds to O2 more readily (transport O2 around body) High pCO2 area = tissues ( body produce CO2 through respiration) —> Hb = lower affinity for O2 .: Releases O2 more readily (more aerobic respiration)
What happens to ODC with fetal haemoglobin?
ODC shifts to the left —> Fetal Hb = higher affinity for O2.
Why does fetal Hb need more O2?
Cannot respire. low pO2 in placenta O2 diffuses from maternal -> fetal blood circulation Increases saturation of fetal HB at lower pO2. Made from 2 alpha + 2 gamma.
What are the different ways of transporting CO2?
5% = dissolved in plasma 10-20% = carbaminohaemoglobin 75-85% = CO2 converted into hydrogencarbonate ions (HCO3-) in RBC –> then transported in plasma.
Describe process of CO2 transportation?
Cell = respire= CO2 Diffuse from tissue fluid -> plasma -> RBC CO2 + H2O ⇋ H2CO3 (catalysed by carbonic anhydrase) H2CO3 = weak acid .: dissociates H2CO3 ⇋ H+ + HCO3- H+ removed by buffers (Hb)
What is the chloride shift?
HCO3- moves out RBC via concentration gradient Cl- ions move into cell Maintain electrical balance of the cell. Travels to lungs Process reverses