5.4 - Gas Exchange In Lungs and Gas Transport in Blood

Question 1

Gas exchange occurs by ___

Answer 1

diffusion

Question 2

In terms of proportionality, rate of diffusion across lungs is:

Answer 2

• proportional to partial pressure gradient
• proportional to available surface area
• inversely proportional to thickness of membranes

Question 3

TRUE OR FALSE:

Rate of diffusion across the lungs is greatest over ____

Answer 3

short distances

Question 4

What factors affect the partial pressure gradient?

Answer 4

composition of inspired air (affected by altitude)

alveolar ventilation (affected by changes in airway resistance and lung compliance)

Question 5

TRUE OR FALSE:

The greater the surface area, the greater the rate of diffusion

Answer 5

TRUE

Question 6

In pulmonary oedema, increase in interstitial fluid in lung leads to ____ in diffusion distance

Answer 6

increase

Question 7

TRUE OR FALSE:

Each haemoglobin molecule can bind up to 4 oxygen molecules

Answer 7

TRUE

Question 8

With what does the oxygen bind in the haeme group?

Answer 8

iron

Question 9

What is oxyhaemoglobin and deoxyhaemoglobin?

Answer 9

haemoglobin bound to O2

Unbound haemoglobin

Question 10

The percent saturation of haemoglobin depends on waht?

Answer 10

% of available binding sites that are bound to O2

Question 11

TRUE OR FALSE:

CO2 is a competitive inhibitor of O2 binding

Answer 11

FALSE

Carbon Monoxide

Question 12

How is CO2 dissolved in plasma?

Answer 12

CO2 is more soluble in body fluids than O2

Question 13

TRUE OR FALSE:

Cells produce less CO2 that can be carried in plasma

Answer 13

FALSE

Question 14

What forms when CO2 interacts with proteins including haemoglobin via 4 terminal amine groups on the protein?

Answer 14

• forms carbaminohaemoglobin (Hb.CO2)

Question 15

Deoxyhaemoglobin interacts ___ readily with CO2 than oxyhaemoglobin

Answer 15

more readily

Question 16

Explain the conversion of CO2 to bicarbonate

Answer 16

• 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)

Question 17

what is respiratory acidosis?

Answer 17

if the Hb buffer is insufficient to absorb all the H+

Question 18

What happens when the venous blood reaches the lungs?

Answer 18

• PCO2 of alveoli is lower than blood
• CO2 dissolved in plasma diffuses into alveoli
• CO2 in RBC diffuses into plasma

Question 19

Explain how the equilibrium of CO2-bicarbonate reaction shifts

Answer 19

bicarbonate ions move from plasma into RBCs (reverse chloride shift)

bicarbonate and H+ form carbonic acid and then CO2 catalyzed by carbonic anhydrase