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Year 1: Respiratory System > 3. Gas Transport and Exchange > Flashcards

3. Gas Transport and Exchange Flashcards

1
Q

What is Dalton’s Law?

A

Partial pressure of a gas mixture is equal to the sum of the partial pressures of gases in the mixture

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2
Q

What is Fick’s law?

A

Molecules diffuse from regions of high conc to regions of low conc at a rate proportional to the concentration gradient, the exchange surface area and the diffusion capacity of the gas, and inversely proportional to the thickness of the exchange surface

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3
Q

What is Henry’s Law?

A

At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

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4
Q

What is Boyle’s Law?

A

At a constant temperature, volume is inversely proportional to pressure

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5
Q

What is Charle’s Law?

A

At a constant pressure, volume is directly proportional to temperature

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6
Q

If the patient has a diffusion problem what must be done?

A

Oxygen therapy: Increase the oxygen given - essentially making the diffusion gradient steeper

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7
Q

With altitude what happens with the gases?

A

The pressure of the atmosphere decreases but the proportions of the gases remains the same

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8
Q

How many kPa of oxygen is in dry air?

A

21.3 kPa

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9
Q

From dry air through the conducting airways how does the air change?

A

There is a slight reduction in pO2 and increase in pH20

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10
Q

How many kPa of of oxygen is in the conducting airways?

A

20 kPa

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11
Q

How many kPa of H2O is in the conducting airways?

A

6.3 kPa

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12
Q

Why is there an increase in the kPa H2O?

A

Because dry air becomes warmed, humidified, slowed and mixed as it passes down the respiratory tree

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13
Q

How many kPa of oxygen is in the respiratory airways?

A

13.5 kPa - this is 100% saturation

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14
Q

What is the solubility of oxygen?

A

You can only dissolve 17 mL of oxygen in your body at 0.34 mL/dL

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15
Q

What is the human oxygen consumption at rest?

A

250 mL/min

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16
Q

What is the structure of haemoglobin?

A

Tetramer - 2 alpha and 2 beta chains, represented as HbA. Each chain has as a ferrous iron ion (Fe2+) which binds 1 molecule of O2.

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17
Q

What chains are in HbA2?

A

2 alpha and 2 delta chains

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18
Q

How many percent of haemoglobin does HbA2 make up?

A

2%

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19
Q

What chains are in foetal haemoglobin (HbF)?

A

2 alpha chains and 2 gamma chain

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20
Q

Describe the affinity to oxygen for haemoglobin?

A

Sigmoid shape - When there is no oxygen bound there is a low affinity. However when the first oxygen binds there is a conformational change increasing its affinity to oxygen.

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21
Q

When oxygen binds to haemoglobin how does the middle change?

A

It becomes a binding site for 2,3-DPG

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22
Q

What is 2,3-DPG a measure of?

A

It is reflective of metabolism. The more ATP produced the more 2,3-DPG produced

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23
Q

What is the function of 2,3-DPG?

A

It is used to squeeze out the oxygen - decreases haemoglobins affinity for oxygen.

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24
Q

Define allosteric

A

It will change shape depending on what is bound or not bound

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25
Q

Define cooperativity

A

It will change its shape and affinity based on how much oxygen is bound

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26
Q

What does a high partial pressure of oxygen mean?

A

It means more oxygen will be dissolved

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27
Q

What is shape of the oxygen dissociation curve?

A

sigmoid curve

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28
Q

What is the oxygen saturation of haemoglobin in alveolar PO2/pulmonary system?

A

It is effectively 100% across a big range of PO2

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29
Q

What is the oxygen saturation of haemoglobin in the tissues/systemic system?

A

In the tissues it can go from 76% to 7% saturated - high unloading capacity

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30
Q

Define P50

A

The partial pressure of oxygen when haemoglobin is 50% saturated

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31
Q

What is P50 good at estimating?

A

The shape of ODC

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32
Q

What is the meaning behind an oxygen dissociation curve shifted to the right?

A

This suggests exercise - decreased affinity to oxygen so increased unloading

33
Q

What happens when you exercise?

A

1) Increase in temperature
2) Acidosis (due to production of lactic acid and excess CO2)
3) Hypercapnia
4) Increase in 2,3-DPG

34
Q

Define hypercapnia

A

Elevated CO2 because there is more cellular metabolism

35
Q

What are the responses when the ODC shifts to the left?

A

Opposite of when it shifts to the right

36
Q

What situation would cause the ODC shift downwards?

A

Anaemic - there is just a lower haemoglobin concentration hence lower amount of oxygen in the blood. However the saturation is the same

37
Q

Less haemoglobin =

A

Lower oxygen carrying capacity

38
Q

Define polycythaemia

A

increase in the packed cell volume (haematocrit) in the blood - it could be due to an increase in the number of RBC

39
Q

What situation would cause the ODC shift upwards?

A

Polycythaemia - increased oxygen carrying capacity

40
Q

What affect does CO have on the ODC?

A

Downards and leftwards shift

41
Q

What does CO do to haemoglobin?

A

It decreases haemoglobin’s capacity for oxygen and increases its affinity.

42
Q

How does CO increase haemoglobins affinity for oxygen?

A

When two of the chains are bound to O2 and the two are bound CO, The two chains bound to O2 will hold the oxygen more tightly

43
Q

What is myoglobin’s effect towards O2?

A

It has a much greater affinity than adult HbA.

44
Q

What is the function of myoglobin?

A

It extracts oxygen circulating in the blood and stores it

45
Q

What is the function of foetal haemoglobin?

A

It has a high affinity so it can steal oxygen from the mother’s blood

46
Q

What the shape of myoglobins ODC?

A

hyperbolic

47
Q

What it the percentage of oxygen saturation arriving at the alveoli?

A

The blood arriving is 75% oxygen bound - not deoxygenated

48
Q

What is the kPa of O2 arriving at the exchange surface of the alveoli in the mixed venous blood?

A

5.3 kPa

49
Q

How does oxygen move from the blood into the RBC?

A

By diffusion. The plasma conc of oxygen is higher than the intraerthrocytic partial pressure of O2

50
Q

What is the percentage saturation of blood when it reaches the tissues?

A

97%

51
Q

Why is percentage saturation of blood not 100% by the time it reaches the tissues from the lungs?

A

It is diluted by bronchial circulation

52
Q

How many circulations does the pulmonary system have?

A

2

53
Q

What changes take place at the tissue?

A

The concentration of oxygen decreases from 20.3 - 15.1 mL/dL

The saturation of oxygen decreases from 97% to 75%

54
Q

Define oxygen flux

A

The overall amount of oxygen being deposited

55
Q

What is the oxygen flux in the tissues?

A

-5 mL/dL this is the amount of oxygen deposited at the tissues

56
Q

How many decilitres are in the body?

A

50 dL

57
Q

What is the resting volume of oxygen consumed?

A

250 mL of oxygen per minute

58
Q

Where does CO2 diffuse into?

A

The blood stream

59
Q

How soluble is CO2?

A

It is more soluble than O2

60
Q

What does CO2 react with in the blood?

A

Water to form carbonic acid H2CO3

61
Q

What does carbonic acid produced in the blood dissociate into?

A

H+ and HCO3-

This is slow reaction - no enzymes

62
Q

What catalyses the reaction converting CO2 to H2CO3 in RBC?

A

Carbonic anhydrase

63
Q

How many times faster does the enzyme in RBC catalyse the reaction?

A

5000 times greater

64
Q

How does bicarbonate produced in the RBC leave and go into the plasma?

A

Via AE1 transporters which moves a chloride ion in

65
Q

What is chloride shift?

A

The movement of Cl- into the RBC while exchanging for HCO3-. Electroneutrality must be maintained across the membrane

66
Q

What does the Cl- ion bring with it when it moves into the RBC?

A

Water, which prevents the cell from dehydrating and getting smaller

67
Q

How/where does carbaminohaemoglobin form?

A

When CO2 binds to the amino end of proteins.

68
Q

How does pH within the RBC maintained with the production of H+ ions?

A

The proteins make good bufffers

69
Q

How does the CO2 flux change from arterial and venous blood?

A

48 to 52mL/dL

70
Q

How many ml of CO2 is produced every minute?

A

200 mL

71
Q

How many ml of oxygen is consumed ever minute?

A

250mL

72
Q

Define respiratory membrane

A

areas where the alveolar cells and endothelial cells of the capillaries are close enough for exchange to take place

73
Q

Define pulmonary transit time

A

This is time where gas exchange can takes place

74
Q

How long is the pulmonary transit time?

A

0.75s however gas exchange will already been completed in 0.25s

75
Q

Define Haldane effect

A

Describes the amount of CO2 that binds to the amine end of the haemoglobin protein changes depending on how much oxygen is bound. Allosteric effect.

76
Q

Will CO2 bind to haemoglobin when O2 saturation is 100%?

A

No, when it starts to unload O2 it becomes more receptive to CO2

77
Q

Which part of the lung is least perfused and why?

A

The apex because of the resistance of gravity

78
Q

Which part of the lung is better ventilated?

A

Bottom of the lung compared to the top

Year 1: Respiratory System (19 decks)

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