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Bio L6 (5) Oxygen and carbon dioxide: gas exchange and transport > Haemoglobin > Flashcards

Haemoglobin Flashcards

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1
Q

What is the main medium for transporting respiratory gases in the body?

A

Blood.

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2
Q

How is carbon dioxide (waste from cell respiration) transported in the blood?

A

As hydrogencarbonate ions.

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3
Q

What type of protein in haemoglobin?

A

A conjugated protein.

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4
Q

Dissect the meaning of the word ‘haemoglobin’.

A 
haem = iron atom, enclosed in a ring structure.
globin = protein part, four chains (2 alpha, 2 beta).
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5
Q

How many prosthetic groups are present in haemoglobin?

A

4, one iron atom for each polypeptide chain.

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6
Q

Describe the structure of a haemoglobin molecule:

A
  • 4 polypeptide chains, 2 alpha and 2 beta.

- Each chain is combined with a prosthetic group called haem.

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7
Q

Each haem group can combine with one molecule of oxygen, what is this process called?

A

Oxygenation.

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8
Q

T / F:

When oxygen attaches to a haem group, oxidation occurs.

A

False, haem loses no electrons, it is called oxygenation.

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9
Q

What determines the degree of oxygenation of haemoglobin?

A

The partial pressure of oxygen pp(O2).

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10
Q

What is meant by pp(O2)?

A

Partial pressure of oxygen.

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11
Q

What happens in haemoglobin if pp(O2) is close or zero?

A

Then no oxygen is bound to the haemoglobin.

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12
Q

What happens in haemoglobin if pp(O2) is low?

A

The polypeptide chains are tightly bound together, making it difficult for oxygen molecules to gain access to the iron and the curve rises gently.

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13
Q

What happens to the dissociation curve if pp(O2) is low?

A

It rises only gently.

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14
Q

What happens in haemoglobin if pp(O2) is very high?

A

The haemoglobin becomes saturated and the curve levels off.

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15
Q

What happens to the dissociation curve if pp(O2) is very high?

A

the curve levels off.

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16
Q

Explain why there is a very steep rise in the dissociation graph:

A

When one molecule of oxygen binds to a haem group, the polypeptide chains open up, exposing the other three haem groups to oxygen. This makes it much easier to bind and the curve rises steeply.

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17
Q

Where in the body is pp(O2) likely to be higher?

A

Lungs.

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18
Q

Where in the body is pp(O2) likely to be lower?

A

Tissues.

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19
Q

How does carbon dioxide affect the relationship between oxygen and haemoglobin?

A

Carbon dioxide decreases the affinity of haemoglobin for oxygen.

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20
Q

Which way does the curve shift in the Bohr shift?

A

Right.

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21
Q

What causes the Bohr shift?

A

The way in which carbon dioxide is transported in the blood.

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22
Q

Why do we need an oxygen transport protein?

A

Oxygen has a low solubility in water and therefore would not be able to get around in hte blood plasma to sufficient levels.

23
Q

Describe in detail the structure of a haem group:

A

A porphyrin ring with an Iron (Fe^2+) ion in the centre.

24
Q

How can a haemoglobin molecule be efficient at transporting oxygen?

A
  • It must readily associate with oxygen at a surface where gas exchange occurs.
  • It must readily dissociate from oxygen at the tissues that require it for respiration.
25
Q

What is the ‘partial pressure’ of a gas?

A

The pressure a particular gas contributes to the total pressure of the gas mixture.

26
Q

Why can’t concentration of gas be used?

A

It isn’t that straightforward, as it depends on more than relative proportions of molecules.

27
Q

Binding of one oxygen molecule induces what change in the globins?

A

From tensed to relaxed, exposing the haem groups and making it easier for subsequent oxygens to bind.

28
Q

In the alveoli the pp(O2) is generally about 15kPa which is less than outside air which is 21kPa, why?

A
  • Alveolar air contains a lot of water vapour;
  • Alveolar air has relatively high concentrations of CO2;
  • There is always residual volume in the alveoli.
29
Q

In the lungs what happens to haemoglobin?

A

They become nearly saturated with oxygen in a fraction of a second.

30
Q

How is carbaminohaemoglobin formed?

A

When carbon dioxide combines with the amino groups in haemoglobin.

31
Q

How is carbon dioxide mainly transported from cells after cellular respiration?

A

Carried mainly in solution as hydrogencarbonate ions.

32
Q

After carbon dioxide diffuses into the red blood cells, what happens to it?

A

It is converted into carbonic acid (H2CO3), the reaction is catalysed by carbonic anhydrase.

33
Q

Which reaction is catalysed by the enzyme carbonic anhydrase?

A

Carbon Dioxide (CO2) -> Carbonic acid (H2CO3).

34
Q

What is formed when carbonic acid dissociates?

A

Protons (H^+) and hydrogencarbonate ions (HCO3^-)

35
Q

How are hydrogencarbonate ions (HCO3^-) transported?

A

In solution in the blood plasma.

36
Q

Why is hte haemoglobin a conjugated protein?

A

It contains polypeptide chains each with prosthetic groups.

37
Q

Why do Chloride ions (Cl^-) diffuse inwards from the plasma to the red blood cells?

A

To maintain electrical neutrality, this is called the chloride shift.

38
Q

What is the Chloride shift?

A

Chloride ions (Cl^-) diffuse inwards from the plasma to maintain electrical neutrality.

39
Q

The protons left inside the red blood cell after the chloride shift are mopped up by haemoglobin, what is formed when they combine?

A

Haemoglobinic acid (HHb).

40
Q

Which acid forces haemoglobin to release its oxygen load creating the Bohr shift?

A

Haemoglobinic acid (HHb).

41
Q

How does the haemoglobin act as a buffer?

A

By taking up excess protons it stops the blood becoming very acidic.

42
Q

Define the Bohr effect?

A

A reduction in the haemoglobin’s affinity for oxygen due to fall in pH, the effect increases with increasing pp(CO2).

43
Q

How does fetal haemoglobin differ in its affinity for oxygen?

A

Fetal haemoglobin has a higher affinity for oxygen than their maternal counterparts, this shifts the curve to the left enabling fetus’ to load oxygen easily.

44
Q

Which way is a fetus’ dissociation curve shifted compared to their mothers?

A

To the left.

45
Q

How does the haemoglobin of animals living in higher altitudes differ in their affinity for oxygen?

A

They have a higher affinity as it ensures their haemoglobin is saturated at lower partial pressures of oxygen due to the reduced atmospheric pressure)

46
Q

Which way is an animal living in high altitudes dissociation curve shifted compared to those at a low altitude?

A

To the left.

47
Q

What is myoglobin?

A

A protein found in muscles which temporarily stores oxygen from the haemoglobin.

48
Q

What is myoglobin’s affinity for oxygen?

A

Higher than haemoglobin so the oxygen is only dissociated at near anaerobic conditions to maximise the storage of oxygen.

49
Q

How does the haemoglobin of animals living in anoxic conditions differ in their affinity for oxygen?

A

They have an extremely high affinity (far left curve) to ensure oxygen binds to haemoglobin and does not immediately dissociate.

50
Q

What is the affinity of an organism living in normal conditions dependant on?

A

The size (SA:V) and metabolic rate.

51
Q

Why do smaller mammals and birds have such a high metabolic rate?

A

It is required to maintain body temperature, a larger SA:V ration means rapid heat loss.

52
Q

Which animal will have a higher affinity for oxygen? An elephant and a mouse?

A

The elephant because it ensures sufficient oxygen reaches all tissues in the large organism.

53
Q

Does the % saturation of haemoglobin with oxygen EVER reach 100%? even in the lungs?

A

No it levels off before and cannot ever be 100% saturated.

54
Q

What enzyme is responsible fore the formation of carbonic acid in red blood cell?

A

Carbonic anhydrase.

Bio L6 (5) Oxygen and carbon dioxide: gas exchange and transport (8 decks)

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