Gas Transport

Question 1

what is gas diffusion

Answer 1

movement of gas throughout the respiratory system occurs via diffusion

Question 2

what are some anatomical and physiological properties that facilitate gas diffusion

Answer 2

• large surface area for gas exchange
• large partial pressure gradients
• gases with advantageous diffusion properties
• specialised mechanisms for transporting oxygen and carbon dioxide between lungs and tissues

Question 3

what is total pressure

Answer 3

the sum of the partial pressures or tensions of a gas

Question 4

what is the barometric pressure at sea level

Answer 4

760 mmHg

Question 5

what is Pgas

Answer 5

partial pressure of a gas

Question 6

what is Fgas

Answer 6

fraction of a gas

Question 7

what does partial pressure equal

Answer 7

Fgas in gas mixture times by barometric pressure

Question 8

what are the two forms of oxygen being carried in the blood

Answer 8

dissolved
bound to haemoglobin

Question 9

describe how dissolved oxygen is measured

Answer 9

clinically in an arterial blood sample

Question 10

how much of oxygen in the blood is dissolved

Answer 10

only a small percentage

Question 11

what is the amount of oxygen dissoved in the blood proportional to

Answer 11

partial pressure

Question 12

how many ml of oxygen per 100ml of blood for each mmHg of PO2

Answer 12

0.003

Question 13

how many litres of oxygen in the blood when the arterial blood has a partial pressure of 100mmHg

Answer 13

3ml

Question 14

is the transport of oxygen in the dissolved form adequate for the body’s requirements

Answer 14

no

Question 15

what is the typical partial pressure of oxygen in the blood for healthy individuals

Answer 15

100mmHg

Question 16

which artery is usually used to provide a sample for calculating partial pressure

Answer 16

radial

Question 17

what does the amount of oxygen dissolved in the blood determine

Answer 17

the partial pressure of oxygen in the blood

Question 18

what is the minimum tissue requirement of oxygen at rest

Answer 18

250ml of oxygen a minute

Question 19

how many litres of blood per minute at rest cardiac output

Answer 19

5 litres

Question 20

what are the tissue requirements for oxygen during strenuous exercise

Answer 20

3000 ml oxygen per minute

Question 21

what is haemoglobin

Answer 21

major transport molecule for oxygen found in red blood cells

Question 22

describe the structure of haemoglobin

Answer 22

four heme groups joined to globin proteins.
two alpha and two beta chains

Question 23

what is heme

Answer 23

iron porphyrin compound

Question 24

what is found in each heme group

Answer 24

iron in reduced ferrous form Fe+++

Question 25

what is the site of oxygen binding in haemoglobin

Answer 25

each ferrous molecule in the heme groups

Question 26

how many haemoglobin molecules per red blood cells

Answer 26

280 million

Question 27

why is it necessary that the binding and dissociation of oxygen from haemoglobin happens in milliseconds

Answer 27

the red blood cells are only in capillaries for one second

Question 28

what does the oxyhemoglobin dissociation curve show

Answer 28

the relationship between partial pressure of oxygen in the blood and the number of oxygen molecules bound to haemoglobin

Question 29

describe what you see

Answer 29

the line is a sigmoid curve. big clinical significance of this shape. flat portion - in a normal healthy individual when the partial pressure of oxygen is 100mmHg, almost up to 100% of haemoglobin molecules are saturated. this means the blood is well oxygenated. steep portion - partial pressure is dropping, but the haemoglobin saturation is stable. this does not change until the gradient of 60mmHg. when the partial pressure drops below this, there is fast dissociation of oxygen from haemoglobin to get more oxygen into the blood to oxygenate the tissues.

Question 30

how many oxygen molecules can bind to each haemoglobin molecules

Answer 30

four

Question 31

what does oxygen saturation refer to

Answer 31

the amount of oxygen bound to haemoglobin relative to maximal amount that can be bound

Question 32

how many ml of oxygen combines with a gram of haemglobin

Answer 32

1.39

Question 33

how many grams of haemoglobin per litre of blood

Answer 33

150g

Question 34

what is the average total oxygen capacity

Answer 34

211ml/s of oxygen per litre of blood

Question 35

what are used to measure oxygen saturation

Answer 35

pulse oximeters

Question 36

how do pulse oximeters work

Answer 36

they measure the ratio of absorption of red and infrared light by oxyHb and deoxyHb

Question 37

how many molecules of carbon dioxide are expired for every 100 molecules of oxygen by the lungs of a healthy person

Answer 37

80

Question 38

what is the respiratory exchange ratio

Answer 38

the ratio of expired carbon dioxide to oxygen uptake

Question 39

what is the respiratory exchange ratio in normal conditions

Answer 39

0.8

Question 40

what are the three forms that carbon dioxide travels the blood in

Answer 40

dissolved bound to haemoglobin converted to bicarbonate

Question 41

how mcuh carbon dioxide in the blood is dissolved

Answer 41

7%

Question 42

how much carbon dioxide in the blood is bound to haemoglobin

Answer 42

23%

Question 43

how much carbon dioxide in the blood is converted to bicarbonate

Answer 43

70%

Question 44

how much carbon dioxide is diffused into red blood cells

Answer 44

93%

Question 45

describe the reaction of carbon dioxide converting to bicarbonate

Answer 45

H2Co3 - carbonic acid HCO3- - bicarbonate

Question 46

what determines the speed of bicarbonate production

Answer 46

concentration gradients

Question 47

what happens to carbon dioxide in systemic capillaries

Answer 47

rightward reaction to form bicarbonate from carbon dioxide. the carbon dioxide is expelled into the blood

Question 48

what happens to carbon dioxide in pulmonary capillaries

Answer 48

leftward reaction to form carbon dioxide from bicarbonate. the carbon dioxide is expelled into the alveoli

Question 49

what does the carbon dioxide to bicarbonate pathway have a key role in

Answer 49

regulation of hydrogen ions and in maintaining acid base balance in the body

Question 50

what can stabilise blood pH

Answer 50

changes in bicarbonate concentrations

Question 51

what makes the buffering reaction strong in the blood

Answer 51

high bicarbonate concentration

Question 52

what can regulate the acidity of the blood

Answer 52

ventilation to adjust the partial pressure of carbon dioxide OR using the kidneys to regulate the bicarbonate concentration

Question 53

what is the shape of the oxygen dissociation curve

Answer 53

sigmoid curve

Question 54

does partial pressure of oxygen have much of an impact on haemoglobin saturation

Answer 54

no

Question 55

what is the enzyme that converts carbon dioxide to carbonic acid

Answer 55

carbonic anhydrase

Question 56

what are some obstructive lung disease

Answer 56

emphysema asthma

Question 57

what are some restrictive lung diseases

Answer 57

pulmonary fibrosis neuromuscular diseases

Question 58

what is the percentage saturation of haemoglobin when PO2 is 10mmHg

Answer 58

10%

Question 59

what is the percentage saturation of haemoglobin when PO2 is 20mmHg

Answer 59

35%

Question 60

what is the percentage saturation of haemoglobin when PO2 is 30mmHg

Answer 60

60%

Question 61

what is the percentage saturation of haemoglobin when PO2 is 40mmHg

Answer 61

75%

Question 62

what is the percentage saturation of haemoglobin when PO2 is 50mmHg

Answer 62

80%

Question 63

what is the percentage saturation of haemoglobin when PO2 is 60mmHg

Answer 63

90%

Question 64

what is the percentage saturation of haemoglobin when PO2 is 70mmHg

Answer 64

90%

Question 65

what is the percentage saturation of haemoglobin when PO2 is 80mmHg+

Answer 65

98%