L11: Exchange & Transport of Gases Flashcards
What determines the DIRECTION of diffusion?
Regions of high partial pressure to low partial pressure, depending on direction of P1-P2 difference
NOT ON CONC DIFF
DEFINE partial pressure
The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.
Finish this
Total pressure (P) =
sum of all the inidividual partial pressures
Define partial pressure
Pressure exerted by an individual gas in a mixture
In the lungs, where does O2 diffuse into from the air?
Into the alveolar fluid
In the lungs, where does CO2 diffuse from, into the air?
From the alveolar fluid
Is diffusion of O2 & CO2 independent of each other?
YES but simultaneous
What is diffusion driven by?
Partial Pressure difference
(Pa-Pc)
A= alveolar
C= capillary
What is diffusion limited by?
Thickness (T) & surface area (A) of diffusion barrier
AND solubility & molecular weight of the gas
Why is concentration difference not so important for diffusion?
Concentration of gas in solution determined by partial pressure & **solubility **
Solubility in H2O only varies if temp varies
What is majority of O2 carried in blood by?
Haeomglobin
Term for process of O2 binding
Oxygenation
Importance of haemoglobin
Increase carrying capacity of O2 to blood
5 factors that changes the way O2 binds to Hb
1) pH
2) pCO2
3) PO2
4) Temp
5) 2,3 diphosphoglycerate
Why is the curve sigmoidal in O2 binding?
O2 binding is co-operative
Binding of 1 O2 increases affinity of remaining 3 binding sites for O2
Factors affecting O2-Hb binding
What does loss of CO2 raise in the alveoli?
Evaporation lowers temp
Left-ward shift = increased affinity of Hb for O2
pH
What does CO2 in tissues lower?
pH
Metabolisms raises temp
Right-ward shift = reduced affinity of Hb for O2
4 important measures of O2 transport
1)** Partial pressure (kPa)**- pressure exerted by gas in air/solution
2) **O2 content (or conc) **- amount of gas present in blood
3)** Percent saturation** - % of O2 binding sites on Hb bound by O2
4) **Maximum O2 carrying capacity **- max amount of O2 carried by particular quantity of Hb
How is O2 transport & delivery in anaemic patients?
Oxygen delivery decreases and oxygen extraction is increased
3 forms of which CO2 is transported
1) Dissolved gas
2) Bicarbonate in plasma
3) Hb bound to carbamino-Hb
Define Haldane effect
The difference in the amount of carbon dioxide carried, at constant Pco2, in oxygenated and deoxygenated blood
How does the Haldane effect work?
A-bicarbonate
CO2 from tissues is converted to HCO3- (bicarbonate) in plasma
How is uptake of CO2 enhanced?
Buffering of H+ by deoxy-Hb more than oxy-Hb
Haldane effect-A
How does the Haldane effect work?
B-carbamino-Hb
CO2 from tissues reacts with lysine & arginie to produce carbamino-Hb
Occurs more readily in deoxy-Hb than oxy-Hb
= Haldane effect-B
