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Cell Biology and Genetics > Haemaglobin and Myoglobin > Flashcards

Haemaglobin and Myoglobin Flashcards

1
Q

What is the structure of haem?

A

Protoporphyrin ring

Fe2+ bound to four nitrogen atoms of that ring

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2
Q

How many bonds is Fe2+ in haem capable of forming?

A

Six

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3
Q

What are the two additional bonds that Fe2+ in haem makes?

A

Bound to globin chain

Bound to oxygen

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4
Q

What shape is the proporyphyrin ring?

A

Planar

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5
Q

What is the spatial arrangement of Fe2+ in the protoporphyrin ring?

A

Fe2+ sits slightly below the plane of the protoporphyrin ring

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6
Q

What is the spatial arrangement of the two additional bonds that Fe2+ in haem forms, compared to the protoporphyrin ring?

A

At right angles to the protoporphyrin ring

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7
Q

What happens to the spatial arrangement of Fe2+ in the protoporphyrin ring when it binds to oxygen? How does this affect the globin protein?

A

Fe2+ moves up into the plane of the protoporphyrin ring
pulls up globin chain
gives small conformational change in haemaglobin

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8
Q

What type of secondary structure does myoglobin have?

A

Mostly alpha helical

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9
Q

What type of tertiary structure does myoglobin have?

A

Mostly globular

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10
Q

What is the name of the graph of x axis-pO2 against y axis-% saturation?

A

Oxygen binding curve

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11
Q

What is pO2?

A

Partial pressure of oxygen

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12
Q

What is P50?

A

Partial pressure of oxygen that gives 50% saturation

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13
Q

What shape does the oxygen binding curve for myoglobin take?

A

Rectangular hyperbola

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14
Q

What type of tertiary structure does haemaglobin have?

A

Globular

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15
Q

What type of quaternary structure does haemaglobin have?

A

Tetramer of

  • 2 alpha globin chains
  • 2 beta globin chains
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16
Q

How many haem groups are there in haemaglobin?

A

Four

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17
Q

What are the the two types of states of haemaglobin?

A

Tense state, T state

Relaxed state, R state

18
Q

What is the affinity of T state haemaglobin for oxygen?

A

Low affinity

19
Q

What is the affinity of R state haemaglobin for oxygen?

A

High affinity

20
Q

What converts T state haemaglobin into R state haemaglobin?

A

Oxygen binding

gives conformational change in haemaglobin

21
Q

What shape does the oxygen bindign curve for haemaglobin take?

A

Sigmoidal curve

22
Q

Why is the oxygen binding curve for haemaglobin sigmoidal?

A

Haemaglobin initially in T state
binding of first oxygen is hard

After first oxygen molecule has bound, haemaglobin in R state
binding of oxygen is then easy

23
Q

What is an advantage of the oxygen binding curve for haemaglobin being sigmoidal?

A

% saturation is more sensitive to smaller changes in pO2

24
Q

What is meant by co-operative binding of oxygen?

A

Haemaglobin’s affinity for oxygen increases as more oxygen molecules bind to it

25
Q

What would be the consequences of no co-operative binding of oxygen in haemaglobin?

A

Haemaglobin always in T state

binds less oxygen

26
Q

How is oxygen binding of haemaglobin regulated?

A

2,3-BPG

Bohr effect

27
Q

Where is 2,3-BPG located?

A

In red blood cells

one molecule bound to one haemaglobin molecule

28
Q

How does 2,3-BPG affect oxygen binding of haemaglobin?

A

Decreases affinity of haemaglobin for oxygen

binds less oxygen

29
Q

What can cause 2,3-BPG levels in red blood cells to increase? Why?

A

High altitude

to ensure more oxygen is released to tissues by haemaglobin

30
Q

What is the Bohr effect?

A

Refers to how binding of H+ and CO2 to haemaglobin

lowers its affinity for oxygen

31
Q

What is the advanage of the Bohr effect?

A

Metabolically active tissues require more oxygen
produce more H+ and CO2
makes haemaglobin release more oyxgen

32
Q

What is meant by the oxygen binding curve for haemaglobin shifting to the right?

A

Need higher pO2 for same % saturation

haemaglobin has a lower affinity for oxygen

33
Q

What is meant by the oxygen binding curve for haemaglobin shifting to the left?

A

Need lower pO2 for same % saturation

haemaglobin has a higher affinity for oxygen

34
Q

What effect does carbon monoxide have on haemaglobin?

A

Binds more tightly to haemaglobin than oxygen does

Causes other CO-free haemaglobin molecules to have higher affinity for oyxgen

35
Q

What are the consequences of carbon monoxide on oxygen transport?

A

Reduced oxygen release to tissues

36
Q

When is carbon monoxide fatal?

A

When it has bound to more than 50% of haemaglobin

37
Q

What is the quarternary structure of fetal haemaglobin?

A

Tetramer made up of:

  • two alpha globin chains
  • two gamma globin chains
38
Q

Does adult haemaglobin or fetal haemaglobin have a higher affinity for oxygen?

A

Fetal haemaglobin

39
Q

What is the importance of fetal haemaglobin having a higher affinity for oxygen than adult haemaglobin?

A

Fetal haemaglobin can extract oxygen from mother’s blood

40
Q

What is the function of haemaglobin?

A

Transport oxygen and CO2

  • pick up oxygen at lungs, release CO2 at lungs
  • pick up CO2 at tissues, release O2 at tissues

Cell Biology and Genetics (32 decks)

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