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The Respiratory System > Respiratory Gas Exchange > Flashcards

Respiratory Gas Exchange Flashcards

1
Q

What are the three dietary “fuels” required for gas transport

A

Fat, carbohydrate and protein

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2
Q

What are the three dietary fuels oxidised to form

A

Carbon Dioxide

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3
Q

What is reduced in the process of oxidation of dietary fuels to form carbon dioxide

A

Coenzymes

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4
Q

What is the role of the mitochondrial electron transport chain in the synthesis of ATP

A

It reduces oxygen (and re-oxidises the coenzymes) to water and the energy released it used to synthesise ATP.

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5
Q

What is the terminal electron acceptor

A

Oxygen

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6
Q

In which direction are oxygen and carbon dioxide transported

A

Oxygen is transported from the lungs to the tissues and carbon dioxide is transported from the tissues to the lungs.

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7
Q

What is the standard unit of pressure

A

Atmospheres

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8
Q

What is one atmosphere in mmHg

A

1 atmosphere = 760 mmHg

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9
Q

What is 1 atmosphere in kPa

A

1 atmosphere = 101 kPa

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10
Q

What is 1kPa in mmHg

A

7.5 mmHg.

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11
Q

What is Daltons Law

A

Each gas in a mixture exerts a pressure independently of the others.

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12
Q

What is atmospheric pressure a sum of

A

The partial pressures of all the gases in the atmosphere.

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13
Q

What is Henry’s Law

A

The concentration of a gas dissolved in a liquid is directly proportional to its partial pressure.

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14
Q

What is the formula for the solution concentration of a gas

A

Solution concentration = kH Pgas
wehre kH is the solubility constant. Since kH is a constant the concentration of a dissolved gas may be expressed as its partial pressure.

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15
Q

Why do different gases have different concentrations in solution even if they have the same partial pressure

A

Because different gases have different solubility constants.

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16
Q

What is gas exchange in the lungs driven by

A

Differences in partial pressure across the alveolar membrane.

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17
Q

What will the concentrations of oxygen and carbon dioxide of inspired air be compared to that in plasma

A

Inspired air will have a higher concentration of oxygen and a lower concentration of carbon dioxide compared to plasma.

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18
Q

Why is equilibrium usually attained in the alveoli

A

Because gas exchange is so rapid

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19
Q

In what situation may equilibrium in the alveoli not be attained

A

If there is a ventilation perfusion mismatch (V/Q mismatch)

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20
Q

Is the rate of diffusion of carbon dioxide or oxygen faster across alveolar membranes

A

Carbon dioxide - by about 20 times.

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21
Q

What happens if gas exchange is slowed, for example if the functional exchange area is reduced

A

Hypoxia (low oxygen) will occur. This is more likely than hypercapnia (high carbon dioxide) because the rate pf diffusion for carbon dioxide is a lot faster than that for oxygen.

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22
Q

What is the function of nitrogen in human metabolism

A

Nitrogen has no function in human metabolism

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23
Q

What is the solubility of nitrogen in the blood

A

Low

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24
Q

When may nitrogen narcosis develop

A

At high pressure nitrogen dissolves in blood and tissues and produces nitrogen narcosis.

25
Q

What happens after nitrogen narcosis when pressure returns to normal

A

Nitrogen emboli may form in capillaries which can cause local ischaemia.

26
Q

Why is such a high percentage of oxygen bound to haemoglobin in the blood

A

Because the solubility of oxygen in the blood is low

27
Q

Around what percentage of oxygen is bound to haemoglobin

A

Around 98.5%

28
Q

What is the oxygen carrying capacity of the blood dependent on

A

The haemoglobin content of the blood.

29
Q

What type of protein is haemoglobin

A

Tetrameric

30
Q

What two subunits is adult haemoglobin composed of

A

2 alpha 2 subunits and 2 beta 2 subunits

31
Q

What two subunits is foetal haemoglobin composed of

A

2 alpha 2 subunits and 2 gamma 2 subunits

32
Q

How many oxygen molecules does one haemoglobin molecule bind

A

Four

33
Q

What happens when oxygen binds to one subunit of haemoglobin

A

There is a conformational change in the protein

34
Q

What are the two conformations of haemoglobin

A

“Oxy” and “deoxy”.

35
Q

What is meant by co-operativity

A

When oxygen binds at one haemoglobin subunit there is a conformational change which results in higher affinity for oxygen at other subunits.

36
Q

What is most often the cause of problems with oxygen delivery

A

Reduced deoxygenation (rather than incomplete oxygenation)

37
Q

What are the factors which favour the release of O2 from haemoglobin

A
  • Increased pH
  • Increased pCO2
  • Increased temperature
38
Q

How does carbon monoxide poisoning result in low oxygen delivery to tissues

A

Carbon monoxide is very similar structurally to oxygen and so can bind to haemoglobin. When it binds, it increases the affinity of haemoglobin for oxygen so release of oxygen is poor and oxygen is not delivered to tissues.

39
Q

How is haemoglobin converted to mathaemoglobin

A

By oxidation of the iron molecule to Fe3+.

40
Q

What is the problem with methaemoglobin

A

It does not bind oxygen

41
Q

Which enzyme converts methaemoglobin back to haemoglobin in erythrocytes

A

Methaemoglobin reductase.

42
Q

What can cause increased levels of mathaemoglobin

A

Genetic mutation favouring the oxidised state.

43
Q

What is the solubility of carbon dioxide in water compared to oxygen

A

Carbon dioxide is much more soluble in water than oxygen.

44
Q

What is produced on hydrating carbon dioxide

A

Carbonic acid

45
Q

How does carbon dioxide bind to haemoglobin

A

It does not bind to the haem groups but reacts with the N-termini amino groups.

46
Q

What is the Haldane effect

A

Deoxygenation of oxygen haemoglobin promotes the binding of CO2 to deoxy-haemoglobin and vice versa.

47
Q

What is most CO2 transported as in the plasma

A

Bicarbonate.

48
Q

What is the order of solubility in water of carbon dioxide, oxygen and nitrogen from lowest to highest

A

Nitrogen (least soluble), oxygen, carbon dioxide (most soluble).

49
Q

In which part of the body is haemoglobin most saturated

A

The lungs. As it travels to the tissues the oxygen gets used up and the haemoglobin becomes less saturated.

50
Q

In which direction does gas move along a pressure gradient

A

From a high partial pressure of that gas to a low partial pressure. This is why oxygen moves across alveolar membranes from the lungs into the plasma.

51
Q

Why does carbon dioxide diffuse faster across membranes compared to oxygen when oxygen is a smaller molecule

A

The diffusion constant of oxygen is greater than that for carbon dioxide because it is a smaller molecule. However, the partition coefficient of carbon dioxide is greater than that of oxygen so CO2 equilibrates faster

52
Q

How does altitude sickness occur

A

If there is an increase in altitude, there is a decrease in the pressure of the air. This means there is less oxygen in the blood and respiration becomes anaerobic to cause altitude sickness.

53
Q

Over what concentration range is haemoglobin released

A

A narrow concentration range.

54
Q

What is the Bohr effect

A

Oxyhaemoglobin becomes protonated so oxygen is released to create deoxyhaemoglobin.

55
Q

What does the binding of 2,3-bisphosphoglycerate do to oxyhaemoglobin

A

Causes it to release oxygen.

56
Q

Why does foetal haemoglobin have a higher affinity for oxygen

A

Because it has a lower 2,3-BPG affinity than adult haemoglobin. 2,3-BPG causes the release of oxygen from haemoglobin so improves delivery to tissues.

57
Q

What is the role of carbonic anhydrase

A

It catalyses the hydration of carbon dioxide to carbonic acid which then ionises to from bicarbonate.

58
Q

What did inhibition of carbonic anhydrase used to be used for

A

Diuretic drugs - particularly acetazolamide because it inhibits the reuptake of sodium and bicarbonate in the kidney.

59
Q

What is acetazolamide (the carbonic anhydrase inhibitor drug) now used most commonly for

A

Preventing altitude sickness by lowering the pH of the blood stimulating respiration and release of O2 from oxyhaemoglobin.

The Respiratory System (20 decks)

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