L11: Exchange & Transport of Gases

Question 1

What determines the DIRECTION of diffusion?

Answer 1

Regions of high partial pressure to low partial pressure, depending on direction of P1-P2 difference

NOT ON CONC DIFF

Question 2

DEFINE partial pressure

Answer 2

The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.

Question 3

Finish this
Total pressure (P) =

Answer 3

sum of all the inidividual partial pressures

Question 4

Define partial pressure

Answer 4

Pressure exerted by an individual gas in a mixture

Question 5

In the lungs, where does O2 diffuse into from the air?

Answer 5

Into the alveolar fluid

Question 6

In the lungs, where does CO2 diffuse from, into the air?

Answer 6

From the alveolar fluid

Question 7

Is diffusion of O2 & CO2 independent of each other?

Answer 7

YES but simultaneous

Question 8

What is diffusion driven by?

Answer 8

Partial Pressure difference
(Pa-Pc)

A= alveolar
C= capillary

Question 9

What is diffusion limited by?

Answer 9

Thickness (T) & surface area (A) of diffusion barrier

AND solubility & molecular weight of the gas

Question 10

Why is concentration difference not so important for diffusion?

Answer 10

Concentration of gas in solution determined by partial pressure & **solubility **

Solubility in H2O only varies if temp varies

Question 11

What is majority of O2 carried in blood by?

Answer 11

Haeomglobin

Question 12

Term for process of O2 binding

Answer 12

Oxygenation

Question 13

Importance of haemoglobin

Answer 13

Increase carrying capacity of O2 to blood

Question 14

5 factors that changes the way O2 binds to Hb

Answer 14

1) pH
2) pCO2
3) PO2
4) Temp
5) 2,3 diphosphoglycerate

Question 15

Why is the curve sigmoidal in O2 binding?

Answer 15

O2 binding is co-operative

Binding of 1 O2 increases affinity of remaining 3 binding sites for O2

Question 16

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

Answer 16

pH

Question 17

What does CO2 in tissues lower?

Answer 17

pH

Metabolisms raises temp
Right-ward shift = reduced affinity of Hb for O2

Question 18

4 important measures of O2 transport

Answer 18

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

Question 19

How is O2 transport & delivery in anaemic patients?

Answer 19

Oxygen delivery decreases and oxygen extraction is increased

Question 20

3 forms of which CO2 is transported

Answer 20

1) Dissolved gas
2) Bicarbonate in plasma
3) Hb bound to carbamino-Hb

Question 21

Define Haldane effect

Answer 21

The difference in the amount of carbon dioxide carried, at constant Pco2, in oxygenated and deoxygenated blood

Question 22

How does the Haldane effect work?
A-bicarbonate

Answer 22

CO2 from tissues is converted to HCO3- (bicarbonate) in plasma

Question 23

How is uptake of CO2 enhanced?

Answer 23

Buffering of H+ by deoxy-Hb more than oxy-Hb

Haldane effect-A

Question 24

How does the Haldane effect work?
B-carbamino-Hb

Answer 24

CO2 from tissues reacts with lysine & arginie to produce carbamino-Hb

Occurs more readily in deoxy-Hb than oxy-Hb
= Haldane effect-B

Question 25

Does Haldane effect reverse or non-reverse in the lungs?

Answer 25

reverse