transport & exchange of gases

Question 1

how to work out total pressure from partial pressures

Answer 1

add up individual partial pressures

Question 2

oxygen diffuses from the air to ….. in lungs

Answer 2

alveolar fluid because PO2 in air is higher than PO2 in alveolar fluid

Question 3

CO2 diffuses from ….. in the lungs into the air

Answer 3

alveolar fluid because PCO2 in alveolar fluid is higher than PCO2 in air

Question 4

CO2 diffusion:
from capillary to alveoli OR alveoli to capillary

Answer 4

capillary to alveoli

Question 5

O2 diffusion:
from capillary to alveoli OR alveoli to capillary

Answer 5

alveoli to capillary

Question 6

main variable influencing diffusion

Answer 6

partial pressure difference

Question 7

PO2 in alveoli and blood equilibrates at ….kPa

Answer 7

13.3 kPa

Question 8

PCO2 in alveoli and blood equilibrates at ….kPa

Answer 8

5.3 kPa

Question 9

PO2 of systemic arterial blood is …. not 13.3kPa

Answer 9

12.5kPa

Question 10

how to work out respiratory quotient

Answer 10

co2 produced/o2 consumed

Question 11

rate of O2 transport = 250 ml/min
rate of CO2 transport = 200 ml/min
why are the volumes different

Answer 11

oxidation of organic fuel produces H20 and CO2

Question 12

majority of O2 is carried in blood by …… which can bind 4 O2
has … at the centre

Answer 12

haemoglobin,
has Fe2+ at the centre

Question 13

why do we need haemoglobin to bind to oxygen

Answer 13

increased capacity of blood to carry oxygen - is poorly soluble in water

Question 14

binding of O2 to haemoglobin is mainly influenced by

Answer 14

PO2

Question 15

binding of O2 to haemoglobin is influenced by PO2 and…. (4)

Answer 15

-PCO2
-pH
-temp
-2,3 DPG

Question 16

O2 binding to Hb is ….. binding 1 O2 increases affinity of remaining 3 binding sites for O2. this means O2-Hb dissociation curve is …

Answer 16

co-operative, sigmoidal

Question 17

O2-Hb dissociation curve - exponential phase of O2 uptake in lungs

Answer 17

small increase in PO2 causes large increase in % saturation.
promotes O2 uptake by Hb in lungs.

Question 18

O2-Hb dissociation curve - plateau phase of O2 uptake in lungs

Answer 18

further changes in PO2 have little effect

Question 19

O2-Hb dissociation curve - plateau phase of O2 unloading in tissues

Answer 19

large drop in PO2 only causes small drop in %saturation

Question 20

O2-Hb dissociation curve - exponential phase of O2 unloading in tissues

Answer 20

small drop in PO2 causes large drop in %saturation.
O2 is more easily released by Hb in tissues where O2 is consumed

Question 21

normal arterial blood at rest is …kPa

Answer 21

12.5kPa

Question 22

mixed venous blood at rest is ….kPa

Answer 22

5.3kPa

Question 23

O2 extracted by tissues at rest = normal aterial blood - mixed venous blood =

Answer 23

20ml - 15ml = 5ml of O2 of blood

Question 24

factors aiding uptake of O2 by Hb in lungs - increased affinity for O2. left or rightward shift of curve

Answer 24

left

Question 25

factors aiding unload of O2 from Hb in tissues where needed - decreased affinity for O2.
left or rightward shift of curve

Answer 25

right

Question 26

factors aiding uptake of O2 by Hb in lungs - increased affinity for O2.
what happens to CO2, pH, temp, 2,3 DPG

Answer 26

Loss of CO2, increased pH, decreased temp, decreased 2,3 DPG

Question 27

factors aiding unload of O2 from Hb in tissues where needed - decreased affinity for O2.
what happens to CO2, pH, temp, 2,3 DPG

Answer 27

Increased CO2, decreased pH, increased temp, increased 2,3 DPG

Question 28

if there’s not enough Hb, how does this lead to mild tissue hypoxia (low tissue PO2) - anaemia

Answer 28

-reduced Hb content (anaemia), reduced oxygen carrying capacity
-tissue PO2 at rest drops from 5.3 to 3.6

Question 29

most CO2 in body is transported as …

Answer 29

bicarbonate in plasma

Question 30

does aterial or venous blood, carry more CO2 as bicarbonate and carbamino

Answer 30

venous blood

Question 31

transport of CO2 in blood -
most is carried as bicarbonate
-then it is carbamino
-least is carried ..

Answer 31

dissolved in plasma

Question 32

does blood have a greater carrying capacity for CO2 or O2

Answer 32

CO2

Question 33

what is the Haldane effect

Answer 33

for a given PCO2, the CO2 content of deoxygenated blood is greater than oxygenated blood

Question 34

PCO2 of normal arterial blood vs mixed venous blood

Answer 34

normal arterial blood - 5.3 kPa
mixed venous blood - 6.1 kPa

Question 35

how is CO2 converted to HCO3- in plasma (slow reaction)

Answer 35

CO2 + H20 –> H2CO3 –> H+ + HCO3-

Question 36

Haldane effect -
how is uptake of CO2 from tissues into erythrocytes converted to HCO3-

Answer 36

CO2 + H2O –> H2CO3 –> H+ + HCO3-

Question 37

Haldane effect -
uptake of CO2 from tissues into erythrocytes converted to HCO3-
what speeds up the reaction

Answer 37

carbonic anhydrase speeds up reaction between CO2 + H2O

Question 38

Haldane effect -
uptake of CO2 from tissues into erythrocytes converted to HCO3-
HOW is uptake of CO2 enhanced

Answer 38

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

Question 39

Haldane effect -
uptake of CO2 from tissues into erythrocytes converted to HCO3-
WHAT is the chloride shift

Answer 39

HCO3- leaves erythrocyte and Cl- enters

Question 40

Haldane effect -
CO2 from tissues enters erythrocyte and binds to Hb (lysine and arginine) to form…

Answer 40

carbamino-Hb

Question 41

Haldane effect -
CO2 from tissues enters erythrocyte and binds to Hb (lysine and arginine) to form carbamino-Hb.
occurs more readily in deoxy-Hb or oxy-Hb

Answer 41

deoxy-Hb

Question 42

Haldane effect in lungs - opposite - so:
1. CO2 released from …
2. …. converted back to CO2
then CO2 diffuses out of blood into alveoli

Answer 42

1. carbamino-Hb
2. HCO3-