Respiration - Gas Transport

Question 1

How do gases move in pressure gradients?

Answer 1

move down the pressure gradient

Question 2

What happens in regards to O2 and CO2 in the pulmonary circuit?

Answer 2

O2 enters blood, CO2 leaves

Question 3

What happens in regards to O2 and CO2 in the systemic circuit?

Answer 3

O2 leaves blood, CO2 enters.

Question 4

Why is the pressure gradient for oxygen much bigger than for carbon dioxide?

Answer 4

CO2 is more diffusible

Question 5

What are the changes in values of PO2 and PCO2 from alveolar air to venous blood in pulmonary capillaries?

Answer 5

Alveolar Air Venous Blood
PO2 100 > 40
PCO2 40 < 46

Question 6

What are the changes in values of PO2 and PCO2 from tissues to arterial blood in systemic capillaries?

Answer 6

Tissues Arterial Blood
PO2 <40 < 100
PCO2 >46 > 40

Question 7

How does movement of gas occur in the respiratory system?

Answer 7

diffusion

Question 8

What properties does the respiration system have that make it good to facilitate gas diffusion?

Answer 8

1) Large surface area for gas exchange.
2) Large partial pressure gradients.
3) Gases with advantageous diffusion properties.
4) Specialised mechanisms for transporting O2 and CO2 between lungs and tissues.

Question 9

How is oxygen carried in blood?

Answer 9

dissolved
bound to Hb

Question 10

What is PaO2?

Answer 10

partial pressure of oxygen in arterial blood

Question 11

What is the amount of dissolved oxygen in blood proportional to?

Answer 11

partial pressure

Question 12

For each mmHg of PO2, how much oxygen is dissolved in blood?

Answer 12

there is 0.003 ml O2/100 ml blood.

Question 13

If arterial blood is 100mmHg PO2, how much oxygen is dissolved in blood?

Answer 13

0.3 ml O2/100ml blood (3ml O2/litre of blood).

Question 14

Why is dissolved oxygen not adequate for body’s requirements?

Answer 14

at rest cardiac output (CO)= 5 L/min.
3ml O2/litre of blood x 5 (CO) = 15ml/min.
BUT tissue requirements at rest 250 ml O2/min.

Question 15

What is the major transport molecule for oxygen?

Answer 15

haemoglobin

Question 16

What is the structure of Hb?

Answer 16

four heme (iron porphyrin compounds) groups joined to globin protein
(two α chains and two β
chains polypeptide chains).

Question 17

What does each heme group contain?

Answer 17

iron in the reduced ferrous
form (Fe+++), which is the
site of O2 binding.

Question 18

How many Hb molecules are in each red blood cells?

Answer 18

280 million

Question 19

How long are RBC in the capillary?

Answer 19

1 sec

Question 20

What does a decrease in pH cause?

Answer 20

a decrease in affinity of haem for oxygen

Question 21

What does an increase in pH cause?

Answer 21

an increase in affinity of haem for oxygen

Question 22

What does a decrease in temperature cause?

Answer 22

an increase in affinity of haem for oxygen

Question 23

What does an increase in temperature cause?

Answer 23

a decrease in affinity of haem for oxygen

Question 24

At what values does a drop in PO2 not cause drastic effects?

Answer 24

100-60 mmHg

Question 25

How many oxygens can haem bind and where is their binding sites?

Answer 25

4 and on iron

Question 26

How much haemoglobin per litre of normal blood?

Answer 26

150g

Question 27

How many ml of oxygen does one g of Hb combine with?

Answer 27

1.39 oxygen

Question 28

How much is the total capacity of oxygen? (dissolved+haem)

Answer 28

211mls O2 per litre

Question 29

What is used to measure O2 and how does it work?

Answer 29

Pulse oximeters used in clinic to measure O2 saturation.

Measures ratio of absorption of red and infrared light by oxyHb and deoxyHb

Question 30

How much ml per minutes of CO2 is produced?

Answer 30

200ml CO2 /min

Question 31

How many molecules of CO2 expired by lung for every 100 molecules of O2?

Answer 31

80

Question 32

What is the ratio of expired CO2 to O2 uptake called?

Answer 32

Respiratory Exchange Ratio

Question 33

What is the normal respiratory exchange ratio?

Answer 33

0.8

Question 34

How is CO2 carried in blood?

Answer 34

7% dissolved.

23% bound to
haemoglobin (Hb).

70% converted to
bicarbonate.

Question 35

What does bicarbonate act as?

Answer 35

buffer

Question 36

How can acidity be regulated?

Answer 36

Acidity can be regulated by using ventilation to adjust the PCO2.

OR via via kidneys to regulate bicarbonate levels

Question 37

What is the equation for bicarbonate?

Answer 37

H2O + CO2 ⇌ H2CO3 ⇌ (H+) + HCO3-

Question 38

In the equation for bicarbonate, what system is the forward reaction (right)?

Answer 38

systemic

Question 39

In the equation for bicarbonate, what system is the backward reaction (left)?

Answer 39

pulmonary