5.4 - Gas Exchange In Lungs and Gas Transport in Blood Flashcards
Gas exchange occurs by ___
diffusion
In terms of proportionality, rate of diffusion across lungs is:
- proportional to partial pressure gradient
- proportional to available surface area
- inversely proportional to thickness of membranes
TRUE OR FALSE:
Rate of diffusion across the lungs is greatest over ____
short distances
What factors affect the partial pressure gradient?
composition of inspired air (affected by altitude)
alveolar ventilation (affected by changes in airway resistance and lung compliance)
TRUE OR FALSE:
The greater the surface area, the greater the rate of diffusion
TRUE
In pulmonary oedema, increase in interstitial fluid in lung leads to ____ in diffusion distance
increase
TRUE OR FALSE:
Each haemoglobin molecule can bind up to 4 oxygen molecules
TRUE
With what does the oxygen bind in the haeme group?
iron
What is oxyhaemoglobin and deoxyhaemoglobin?
haemoglobin bound to O2
Unbound haemoglobin
The percent saturation of haemoglobin depends on waht?
% of available binding sites that are bound to O2
TRUE OR FALSE:
CO2 is a competitive inhibitor of O2 binding
FALSE
Carbon Monoxide
How is CO2 dissolved in plasma?
CO2 is more soluble in body fluids than O2
TRUE OR FALSE:
Cells produce less CO2 that can be carried in plasma
FALSE
What forms when CO2 interacts with proteins including haemoglobin via 4 terminal amine groups on the protein?
- forms carbaminohaemoglobin (Hb.CO2)
Deoxyhaemoglobin interacts ___ readily with CO2 than oxyhaemoglobin
more readily
Explain the conversion of CO2 to bicarbonate
- majority of CO2 entering blood is converted to bicarbonate ions by the enzyme carbonic anhydrase (present in RBCs)
- bicarbonate ions are moved out of RBC by transporter protein which exchanges HC03- for Cl- (chloride shift)
what is respiratory acidosis?
if the Hb buffer is insufficient to absorb all the H+
What happens when the venous blood reaches the lungs?
- PCO2 of alveoli is lower than blood
- CO2 dissolved in plasma diffuses into alveoli
- CO2 in RBC diffuses into plasma
Explain how the equilibrium of CO2-bicarbonate reaction shifts
bicarbonate ions move from plasma into RBCs (reverse chloride shift)
bicarbonate and H+ form carbonic acid and then CO2 catalyzed by carbonic anhydrase
