Physiology - Gas transport

Question 1

Effect of partial pressure on gas solubility?

This is an example of?

Answer 1

Amount of gas dissolved is proportional to the partial pressure of the gas at equilibrium with the liquid.
Henry’s law.

Question 2

How many mls of O2 are in a litre of blood?

Answer 2

3.

Question 3

How is most O2 transported in the blood?

Answer 3

Bound to haemoglobin.

Question 4

What is the normal partial pressure of O2?

Answer 4

13.3 kPa.

Question 5

How is oxygen found in the blood?

Answer 5

Bound to haemoglobin or physically dissolved.

Question 6

Normal haemoglobin conc?

Answer 6

150 g/l.

Question 7

How many haem groups does a Hb molecule have?

Answer 7

4.

Question 8

When is haemoglobin fully saturated?

Answer 8

When all Hb present is carrying it maximal O2 load.

Question 9

What is the primary factor which determines the percent saturation of Hb with O2?

Answer 9

PO2.

Question 10

What does oxygen delivery depend on?

Answer 10

Oxygen content of arterial blood and cardiac output.

Question 11

Oxygen Delivery Index equation.

Answer 11

DO2l = CaO2 * Ci

CaO2 - Oxygen content in arterial blood (ml/l)
Ci - cardiac index relates to cardiac output to the body surface area.

Question 12

When is oxygen delivery to tissues impaired?

Answer 12

Decreased PP of inspired oxygen.

Resp disease (decreased Hb saturation with O2).

Anaemia (decreases Hb conc and therefore O2 content in blood).

Heart failure (decreases CO).

Question 13

Describe cooperativity.

Answer 13

Bindingof one O2 to Hb increases the affinity of Hb for O2 giving a sigmoid shape graph that flattens out as all sites become occupied,

Question 14

Significance of sigmoid graph?

Answer 14

Flat upper portions means that moderate fall in alveolar PO2 will not much affect oxygen loading.

Steep lower part
means that the peripheral tissues get a lot of oxygen for a small drop in capillary PO2.

Question 15

Describe myoglobin.

Answer 15

Present In skeletal and cardiac muscles.

Only 1 haem group therefore no cooperativity.

Hyperbolic dissociation curve.

Releases O2 at very low PO2.

Presence in blood indicates muscle damage.

Question 16

How does foetal haemoglobin differ from adult?

Answer 16

2 alpha and 2 gamma subunits.

interacts less with 2,3-Biphosphoglycerate in RBC’s and hence has a higher affinity for O2 and dissociation curve is shifted to the left.

Question 17

What does a higher affinity for O2 in HbF allow?

Answer 17

O2 to transfer from mother to foetus even if PO2 is low.

Question 18

What is the Bohr effect?

Answer 18

A shift of the curve to the right.

Question 19

Where must CO2 produced in the tissues travel to in order to be removed from the body?

Answer 19

Lungs.

Question 20

How can CO2 be transported in the blood?

Answer 20

Solution (10%)
As bicarbonate (60%)
As carbamino compounds (30%).

Question 21

Is O2 or CO2 more soluble?

Answer 21

CO2 20 times more soluble.

Question 22

How is most CO2 transported in the blood?

Answer 22

As bicarbonate.

Question 23

What facilitates the formation of bicarbonate in the blood? Where is this found?

Answer 23

Carbonic Anhydrase.

RBC’s.

Question 24

What intermediate is formed in formation of bicarbonate?

Answer 24

Carbonic Acid. H2CO3.

Question 25

Reaction of formation of bicarbonate in the blood?

Answer 25

CO2 + H20 —> H2CO3 —–> H+ + HCO-3

Question 26

What is the exchange of chloride and bicarbonate called?

What moves where?

Answer 26

Chloride shift.

Bicarbonate moves out of RBC to capillary wall and chloride moves into RBC.

Question 27

What are carbamino compounds formed by?

Answer 27

Combination of CO2 and terminal amine groups in blood proteins.

cambamino-haemoglobin is common when CO2 combines with haem group.

Question 28

What gas does reduced Hb bind more of?

Answer 28

CO2 than O2.

Question 29

The Haldane effect?

Answer 29

Removing O2 from Hb increases ability Hb to pick up CO2 and generate H+.

Question 30

Combined affects of Bohr and Haldane facilitate what?

Answer 30

O2 liberation and uptake of CO2 and CO2 generated H+.

Question 31

What does the Bohr effect facilitate?

Answer 31

Removal of O2 from haemoglobin at tissues by shifting dissociation curve to right.

Question 32

CO2 and O2 transfer in systemic and pulmonary circulation.

Answer 32

Systemic - O2 moves into tissues, CO2 moves out of tissues.

Pulmonary - O2 moves out of alveoli and CO2 moves into alveoli.

Question 33

What can bind to Hb? (3)

Answer 33

O2
CO2
H+

Question 34

How does bicarb move out of RBC?

Answer 34

Down its concentration gradient.

Question 35

How does chloride move into RBC?

Answer 35

passively, down its electrical gradient.