Lecture 23 - O2 And CO2 Transfer Between Alveolus, Blood And Tissue

Question 1

Where does gas exchange occur

Answer 1

Across the blood-gas barrier

Question 2

Gas exchange across the alveolus occurs by

Answer 2

Diffusion

Question 3

What is Ficks law of diffusion

Answer 3

Dt = (Kt)(S)(1/Tnt)

Question 4

In what to forms is the oxygen transported in blood

Answer 4

Physically and chemically

Question 5

How is oxygen physically transported

Answer 5

Plasma soluble oxygen (2%)

Question 6

Why is there a partial pressure of oxygen in the alveolus

Answer 6

As plasma soluble oxygen is less soluble than carbon dioxide

Question 7

How is oxygen transported chemically

Answer 7

By being bound to haemoglobin

Question 8

What is the interaction between oxygen and Hb like

Answer 8

It is rapid and reversible

Question 9

What does the reversibility of the oxygen-Hb bond allow

Answer 9

For oxygen to off-load onto tissues

Question 10

How is oxygen content determined

Answer 10

By the amount of Hb and oygen in the blood

Question 11

What is oxygen saturation

Answer 11

The proportion of oxygen-saturated Hb relative to the total Hb in the blood

Question 12

What does the P50 value represent

Answer 12

The Poxygen required for half the maximal Hb saturation

Question 13

What pressure does the venous blood enter the alveolus at

Answer 13

40mmHg

Question 14

What doe sthe arterial plateau phase ensure

Answer 14

That maximal Hb-oxygen saturation even in alveolar Poxygen is below the normal oxygen level

Question 15

What does normoxic mean

Answer 15

Normal levels of oxygen

Question 16

What does the steep phase of the oxygen-haemoglobin dissociation curve favour

Answer 16

Off-loading of arterial oxygen to tissues

Question 17

What happens to the Hb-oxygen dissociation for small changes in the tissue Poxygen

Answer 17

There is greater Hb-oxygen dissociation

Question 18

What factors shift the oxyhaemoglobin dissociation curve to the left

Answer 18

Foetal Hb

Question 19

What happens when the oxyhaemoglobin dissociation curve is shifted to the left

Answer 19

There is an increased Hb-oxygen affinity and a reduced carbon dioxide off-loading

Question 20

What factors shift the oxyhaemoglobin dissociation curve to the right

Answer 20

Fever, hypoxic glycolysis and the Bohr effect

Question 21

What causes the Bohr effect

Answer 21

Acidosis and an increase in Pcarbon dioxide

Question 22

What happens when the oxyhaemoglobin dissociation curve is shifted to the right

Answer 22

There is a decreased Hb-oxygen affinity and an increased carbon dioxide off-loading

Question 23

What is Hb

Answer 23

A heterotetramer

Question 24

What is Hb composed of

Answer 24

2 alpha and 2 beta subunits

Question 25

What does Hb contain

Answer 25

4 iron-binding HEME domains

Question 26

Within Hb what is the oxygen bound to

Answer 26

The Fe3+ ions in the centre of the HEME ring

Question 27

What alters the affinity of oxygen to Hb

Answer 27

Carbon dioxide, pH and 2,3 BPG

Question 28

How do carbon dioxide, pH and 2,3 BPG cause a change in affinity of oxygen to Hb

Answer 28

By interacting with the charged amino groups between the alpha and beta subunits

Question 29

What does the amino terminus of the Hb-alpha subunit bind to

Answer 29

The carboxy-terminal histidine in the beta subunit

Question 30

The interaction between the Hb-alpha subunit and the carboxy-terminal histidine in the beta subunit is sensitive to what

Answer 30

pH and carbon dioxide

Question 31

What happens to interactions during acidosis

Answer 31

The decreased pH favours the alpha-beta interaction and reduces the binding of oxygen to the HEME

Question 32

WHat effect does carbon dioxide have

Answer 32

It lower blood pH and reduces Hb affinity for oxygen

Question 33

In what two ways does increased Pco2 release o2 from Hb

Answer 33

The production of carbonic acid in the red blood cells and the carbamate reaction at the N-terminal amno group of the Hb alpha-subunit

Question 34

What effect does carbon monoxide have on the oxyhaemoglobin curve and why

Answer 34

Its afiinity for Hb is 240 times greater than oxygen, it forms carboxyhaemoglobin and causes the curve to shift left which reduces oxygen off-loading

Question 35

What effect does anemia have on the oxyhaemoglobin curve

Answer 35

It causes it to shift right as the oxygencapacity is lowered

Question 36

How is carbon dioxide carried physically

Answer 36

By plasma soluble carbon dioxide

Question 37

What are the two forms of plasma soluble carbon dioxide

Answer 37

Soluble carbon dioxide gas (5%) or the bicarbonate ion (90%)

Question 38

How is carbon dioxide chemically transported

Answer 38

through carbamino haemoglobin (5%)

Question 39

What is the carbon dioxide dissociation curve altered by

Answer 39

Tissue oxygenation

Question 40

What improves the carriage of carbon dioxide

Answer 40

The deoxygenation of blood

Question 41

What effect is tissue oxygenation

Answer 41

The Haldane effect

Question 42

What do the Bohr and Haldane effects enable

Answer 42

Reciprocal oxygen and carbon dioxide gas exchange

Question 43

What defines the ventilation:perfusion relationship in the lung

Answer 43

Oxygen and carbon dioxide

Question 44

Where does the oxygen equilibriate from

Answer 44

The alveolus to the blood

Question 45

Where does the carbon dioxide equilibriate from

Answer 45

The blood to the alveolus

Question 46

What allows fine tuning of oxygen uptake and carbon dioxide clearing

Answer 46

Breathing and lung-perfusion

Question 47

in what situation is the fine tuning of oxygen uptake and carbon dioxide clearing needed

Answer 47

High altitude mountaineering, tolerance of G-force and external pressure (diving)

Question 48

Equation to calculate alveolar Poxygen

Answer 48

pAoxygen = F1oxygen(pATM-SVP)-pAcardon dioxide(F1oxygen + (1-F1oxygen)/RQ))