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Biochem Take 2. > Haemoglobin and Myoglobin. > Flashcards

Haemoglobin and Myoglobin. Flashcards

1
Q

A globular protein is in what form of protein structure?

A

Tertiary.

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2
Q

What are the characteristics of a globular protein?

A

They are spherical in shape.

They are water soluble.

They can be used as transport proteins or enzymes.

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3
Q

If a globular protein contains heme, where will the heme likely be found?

A

Heme will be bound to a domain within the globular protein.

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4
Q

Heme is an example of what kind of protein attachment?

A

A prosthetic group.

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5
Q

What are the functions of hemeproteins?

A

They can function as electron carriers.

They can be part of an active site.

Transport of O2 and CO2.

Storage of O2.

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6
Q

What are 2 examples of hemeproteins?

A

Myoglobin.

Haemoglobin.

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7
Q

What is the structure of heme?

A

A porphyrin ring with an iron atom at its centre.

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8
Q

The porphyrin ring of heme is an example of what kind of protein feature?

A

A coenzyme.

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9
Q

The iron atom of heme is an example of what kind of protein feature?

A

A cofactor.

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10
Q

How many bonds can iron form?

A

6.

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11
Q

How does iron bind to the porphyrin ring?

A

4 of the bonds are bound to 4 nitrogen atoms that are part of the porphyrin ring.

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12
Q

Heme will insert itself into what level of structure in myoglobin?

A

The tertiary structure.

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13
Q

Heme will insert itself into what level of structure in haemoglobin?

A

The quaternary structure.

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14
Q

Where does oxygen bind to in myoglobin or haemoglobin?

A

To the heme molecule.

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15
Q

What part of the heme molecule will oxygen bind to?

A

The iron atom.

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16
Q

What are the 2 free bonds of iron bonded to when heme is oxygeated.

A

One bond is bound to one of the oxygens of O2.

One bond is bound to proximal histidine.

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17
Q

What is oxygen bound to within the heme molecule?

A

One oxygen is bound to the iron of heme.

One is bound to distal histidine.

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18
Q

Why does an oxygen atom bind to distal histidine?

A

Because the distal histidine stabilises the oxygen.

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19
Q

What does the proximal histidine do to for heme molecule?

A

It stabilises the positioning of heme.

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20
Q

What shape is de-oxygenated heme?

A

Non planar.

It is domed.

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21
Q

What shape is oxygenated heme?

A

It is planar.

The bonding of oxygen to heme straightens it out.

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22
Q

What is the function of myoglobin?

A

Myoglobin is used for storing oxygen.

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23
Q

Describe the secondary structure of myoglobin?

A

It is made up of many different alpha helices that are separated by beta bends and random loops.

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24
Q

Where is heme located in myoglobin?

A

In a domain at the centre of the protein.

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25
Q

How many oxygens does myoglobin bind to?

A

1.

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26
Q

Does myoglobin suffer from allosteric effectors?

A

No.

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27
Q

Myoglobin is at what level of protein structure?

A

Tertiary.

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28
Q

Is myoglobin a single or multiple polypeptide?

A

A single polypeptide.

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29
Q

Where is haemoglobin found in the body?

A

Only in red blood cells.

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30
Q

What is the function of haemoglobin?

A

To transport oxygen around the body.

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31
Q

What level of protein structure is haemoglobin at?

A

Quaternary.

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32
Q

How many polypeptides make up haemoglobin?

A

4.

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33
Q

How are the 4 subunits of haemoglobin divided up?

A

Into an alpha dimer and a beta dimer.

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34
Q

How are the 4 dimers of heme arranged?

A

Dimer 1 is made of an 1 alpha dimer and a beta dimer.

Dimer 2 is made up of a beta dimer and an alpha dimer.

35
Q

How many heme molecules are found in haemoglobin?

A

4.

36
Q

How many heme molecules are found in myoglobin?

A

1.

37
Q

How many oxygens can haemoglobin bind to?

A

4.

38
Q

What holds the dimers of haemoglobin together?

A

Non covalent bonds.

39
Q

What happens to the bonds that hold the 2 dimers together when an oxygen binds to a heme?

A

Some of the bonds are broken so the forces holding the 2 hemes together are weaker.

40
Q

What is the taut form of haemoglobin?

A

The form of haemoglobin that is not bound to oxygen.

This is because the bonds holding the dimers together are stronger as there are more of them.

41
Q

What is the relaxed form of haemoglobin?

A

The form of haemoglobin that is bound to oxygen.

This is because the bonds holding the dimers together are weaker as there are fewer of them.

42
Q

What kind of affinity for oxygen does taut haemoglobin have?

A

Low affinity.

43
Q

What kind of affinity for oxygen does relaxed haemoglobin have?

A

High affinity.

44
Q

How does the affinity of haemoglobin to oxygen change?

A

It changes depending on the amount of oxygen available.

45
Q

What are the allosteric effectors that influence hemes binding affinity for oxygen?

A

Partial pressure of oxygen

pH of the environment.

Partial pressure of CO2.

The availability of 2,3-bisphosphoglycerate.

46
Q

Does myoglobin have a high or low affinity for oxygen?

A

Very high.

47
Q

What happens to haemoglobin’s affinity for oxygen when an oxygen molecule binds to de-oxygenated heme?

A

As more oxygen binds to haemoglobin its affinity for oxygen will increase.

When 1 oxygen binds to a heme group, the affinity for oxygen of the other heme groups increases.

48
Q

Is the partial pressure of oxygen higher in the tissues or the lungs?

A

The lungs.

49
Q

Myoglobin has what kind of shape on an oxygen dissociation graph?

A

Hyperbolic.

50
Q

What does the p50 of myoglobin or haemoglobin represent?

A

The partial pressure of oxygen where they will lose 50% of their oxygen.

51
Q

Is the P50 higher form myoglobin or haemoglobin?

A

Haemoglobin.

52
Q

In what organ will haemoglobin be fully saturated with oxygen?

A

In the lungs.

53
Q

What happens when haemoglobin travels away from the lungs and goes to the tissues?

A

It will lose oxygen as the partial pressure of oxygen decreases.

54
Q

What shape is haemoglobin on an oxygen dissociation graph?

A

Sigmoidal.

55
Q

What happens when haemoglobin is shifted to the left on the oxygen dissociation graph?

A

Its affinity for oxygen will increase.

56
Q

What happens when haemoglobin is shifted to the right on the oxygen dissociation graph?

A

Its affinity for oxygen will decrease.

57
Q

How strong are the bonds between the 1st O2 to bind to haemoglobin and the hem group?

A

They are very weak.

As each subsequent oxygen binds to its heme, the bonds to each one will get stronger.

58
Q

Why does haemoglobin off load O2 in the tissues?

A

Because the partial pressure of O2 is much lower in the tissues.

59
Q

What happens when haemoglobin has off loaded all of its oxygens?

A

It will start to pick up CO2 molecules that have been made by the tissues.

60
Q

What happens to CO2 once it has bound to heme?

A

It will be transported back to the lungs where it will be exhaled.

61
Q

Does CO2 bind to the heme groups in haemoglobin?

A

No.

CO2 binds to the 4 amino groups of the subunits that make up haemoglobin.

62
Q

What can compete with O2 to bind with haemoglobin?

A

Carbon monoxide.

63
Q

Does heme have stronger affinity for CO2 or CO?

A

CO.

64
Q

What effect will 1 CO molecule that is bound to a heme have on the 3 other heme molecules in haemoglobin?

A

If one heme is bound to a CO, then it will affect the affinity for oxygen of the other heme groups and they will form much stronger bonds with oxygen.

65
Q

How does heme behave if it is bound to 1 CO and 3 O2’s?

A

It will behave like myoglobin and will not deliver O2 to the tissues.

66
Q

What will shift the oxygen dissociation curve of haemoglobin to the left and changes the sigmoidal curve to a hyperbolic curve?

A

If carbon monoxide is bound to a heme molecule.

67
Q

What kind of acid is formed when there are high levels of CO2 within the body?

A

Carbonic acid which dissociates to form bicarbonate and H+.

68
Q

What affect does high levels of CO2 have on the pH in that area of the body?

A

High levels of CO2 will decrease the pH.

69
Q

What affect does low pH have on haemoglobin?

A

Any drop in pH will make it easier for haemoglobin to off load oxygen to the affected area.

70
Q

What is the Bohr effect?

A

The decreased affinity of haemoglobin for oxygen under acidic conditions.

71
Q

An increase in CO2 leads to what in the surrounding tissues?

A

Acidification.

72
Q

How can a drop in pH due to increased CO2 levels be corrected?

A

By adding more O2 to the affected area.

73
Q

When are the bonds between the 2 dimers of haemoglobin at their strongest?

A

When haemoglobin has no oxygen bound to it.

74
Q

Does deoxygenated haemoglobin have low or high affinity for O2?

A

Low.

75
Q

How does tissue acidification affect the structure of haemoglobin?

A

The structure of haemoglobin will go from the relaxed form to the taut form by increasing the number of bonds between the subgroups.

76
Q

If the amount of CO2 increases, or the pH decreases, how will this affect the oxygen dissociation curve of haemoglobin?

A

It will shift it to the right, representing haemoglobins decreased affinity for oxygen.

77
Q

If the amount of CO2 decreases, or the pH increases, how will this affect the oxygen dissociation curve of haemoglobin?

A

It. will shift to the left, representing haemoglobins increased affinity for oxygen.

78
Q

Hb-O2 + H+ = ???

A

Hb-H+ + O2.

79
Q

When is 2,3-bisphosphoglycerate made?

A

During glycolysis.

80
Q

Where does 2,3-BPG locate itself in the haemoglobin molecule?

A

In the positively charged cavity between the 4 subunits of haemoglobin.

81
Q

What effect does 2,3-BPG have on haemoglobin?

A

It stabilises the de-oxy form of oxygen allowing for oxygen to be offloaded much more easily.

82
Q

What will increase the concentration of 2,3-BPG in haemoglobin?

A

When a person is at high altitudes.

83
Q

An increased amount of 2,3-BPG will shift the oxygen dissociation curve for Hb in what direction?

A

If the concentration of 2,3-BPG is increased, it will shift the oxygen dissociation curve to the right.

Biochem Take 2. (24 decks)

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