gas transport in the blood (R5)

Question 1

what must happen to O2 picked up by the blood at the lungs

Answer 1

must be transported to the tissues for cellular use

Question 2

what must happen to CO2 produced at tissues

Answer 2

must be transported to the lungs for removal

Question 3

ways CO2 can be transported in the blood

Answer 3

• solution (10%)
• as bicarbonate (60%)
• as carbamino compounds (30%)

Question 4

what is the effect of partial pressure on gas solubility (Henry’s Law)

Answer 4

-the amount of a given gas dissolve in a given type and volume of liquid (eg. blood) at a constant temperature is proportional to the partial pressure of the gas that is in equilibrium with the liquid

Question 5

what happens to the concentration of a gas in the liquid phase if the partial pressure in the gas phase is increased

Answer 5

-concentration in liquid phase would increase proportionally (henry’s law)

Question 6

partial pressure of a gas in solution (as a result of Henry’s law)

Answer 6

= its partial pressure in the gas mixture with which it is in equilibrium

Question 7

solubility of CO2

Answer 7

• henry’s law (gas dissolve in liquid, eg. blood is proportional to the partial pressure of the gas that is in equilibrium with the liquid)
• CO2 is about 20 times more soluble than oxygen (about 20% of CO2 is in solution)

Question 8

what is the most common way of CO2 transport in the blood

Answer 8

CO2 transport as bicarbonate

Question 9

how is bicarbonate formed in the blood

Answer 9

• reversible conversion of dissolved bicarbonates and carbon dioxide with help of the enzyme carbonic anhydrase (reaction between carbonic acid and water gives you H2CO3 which can then be divided to HCO3- and H+ ions, HCO3- = bicarbonate)
• occurs in red blood cells
• the H+ produced, joins with Hb in red blood cells forming HHb
• this form of transport of CO2 within the blood involves a chloride shift to transport bicarbonate from one RBC to another until it reaches the alveolus (for example chloride is taken up into one RBC in exchange for bicarbonate leaving the RBC, then chloride is released from another RBC in exchange for bicarbonate being taken up by that RBC)

Question 10

carbonic anhydrase

Answer 10

-an enzyme that catalyzes the interconversion of dissolved bicarbonates and carbon dioxide

Question 11

carbamino compounds formation

Answer 11

• formed by combination of CO2 with terminal amine groups in blood proteins
• especially with globin of haemoglobin to form carbamino-haemoglobin
• rapid even without enzyme
• reduced Hb (reduction = loss of O2) can bind more CO2 than HbO2 (oxidised Hb)

Question 12

the Haldane effect

Answer 12

-removing O2 from Hb increases the ability of Hb to pick up CO2 (to form carbamino-haemoglobin/carbamino compounds) and CO2 generated H+ (from bicarbonate production)

Question 13

relationship between the bohr effect and the Haldane effect

Answer 13

• the bohr effect and the Haldane effect work in synchrony to facilitate O2 liberation and uptake of CO2 and CO2 generated H+ at tissues
• The bohr effect facilitates the removal of O2 from haemoglobin at tissue level by shifting the oxygen haemoglobin dissociation curve to the right (towards tissue conditions)

Question 14

dissociation

Answer 14

the disconnection or separation of something from something else or the state of being disconnected

Question 15

CO2 dissociation curve

Answer 15

• oxygen shifts the CO2 dissociation curve to the right (Haldane effect)
• straight line due to henry’s law (concentration of CO2 in liquid/aka blood is directly proportional to the partial pressure of CO2 in gas phase)

Question 16

PO2 in mixed venous blood

Answer 16

5.3

Question 17

PO2 in arterial blood

Answer 17

13.3

Question 18

effect of O2 on binding of CO2 and H+ to Hb

Answer 18

-at the lungs the Hb pick up the O2, this weakens Hb’s ability to bind CO2 and H+

Question 19

summary of CO2 transport in the blood

Answer 19

• CO2 released at level of tissue cell into plasma, dissolved CO2 in plasma diffuses into RBC and has 3 mechanisms of which it is transported in the blood:
• > 1-as dissolved CO2
• > 2-is taken up by Hb (that is released from unbinding of O2 from Hb at tissue cell, HbO2 -> Hb + O2) forming carbamino-haemoglobin/carbamino compounds
• > 3-CO2 reacts with water and carbonic anhydrase converts it to dissolved bicarbonates which can be converted to bicarbonate and H+, the CO2 can be transported as bicarbonate and Hb (released from the unbinding of O2 from Hb at the tissue cell) can bind to H+ (CO2 generated H+), this form of transport involves a chloride shift to transport bicarbonate from one RBC to another until it reaches the alveolus (for example chloride is taken up into one RBC in exchange for bicarbonate leaving the RBC, then chloride is released from another RBC in exchange for bicarbonate being taken up by that RBC)
• from systematic circulation to pulmonary circulation:
• chloride shift occurs to release chloride from RBC and uptake bicarbonate which combines with H+ (which is released from HbH, HbH -> Hb + H+) to form H2CO3, carbonic anhydrase breaks this down into CO2 and H2O)
• CO2 is also released from carbamino-haemoglobin (HbCO2 -> CO2 + Hb)
• at the lungs the Hb pick up the O2, this weakens Hb’s ability to bind CO2 and H+, therefore the O2 diffused into the blood (RBC) at the alveolus is what causes the release of CO2 from Hb/carbamino-haemoglobin and the release of CO2 generated H+ from Hb, and oxygen binds with Hb instead to be transported to the tissue cell where it is released and the cycle starts again
• all CO2 now present in the RBC from the release of its transport mechanisms and in the form of dissolved CO2, are released into the alveolus

Question 20

systematic circulation

Answer 20

the main part of the blood circulation, as distinct from the pulmonary circulation

Question 21

pulmonary circulation

Answer 21

the blood flow through the network of vessels between the heart and the lungs for the oxygenation of blood and removal of carbon dioxide