Haemaglobin and Myoglobin

Question 1

What is the structure of haem?

Answer 1

Protoporphyrin ring

Fe2+ bound to four nitrogen atoms of that ring

Question 2

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

Answer 2

Six

Question 3

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

Answer 3

Bound to globin chain

Bound to oxygen

Question 4

What shape is the proporyphyrin ring?

Answer 4

Planar

Question 5

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

Answer 5

Fe2+ sits slightly below the plane of the protoporphyrin ring

Question 6

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

Answer 6

At right angles to the protoporphyrin ring

Question 7

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

Answer 7

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

Question 8

What type of secondary structure does myoglobin have?

Answer 8

Mostly alpha helical

Question 9

What type of tertiary structure does myoglobin have?

Answer 9

Mostly globular

Question 10

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

Answer 10

Oxygen binding curve

Question 11

What is pO2?

Answer 11

Partial pressure of oxygen

Question 12

What is P50?

Answer 12

Partial pressure of oxygen that gives 50% saturation

Question 13

What shape does the oxygen binding curve for myoglobin take?

Answer 13

Rectangular hyperbola

Question 14

What type of tertiary structure does haemaglobin have?

Answer 14

Globular

Question 15

What type of quaternary structure does haemaglobin have?

Answer 15

Tetramer of

• 2 alpha globin chains
• 2 beta globin chains

Question 16

How many haem groups are there in haemaglobin?

Answer 16

Four

Question 17

What are the the two types of states of haemaglobin?

Answer 17

Tense state, T state

Relaxed state, R state

Question 18

What is the affinity of T state haemaglobin for oxygen?

Answer 18

Low affinity

Question 19

What is the affinity of R state haemaglobin for oxygen?

Answer 19

High affinity

Question 20

What converts T state haemaglobin into R state haemaglobin?

Answer 20

Oxygen binding

gives conformational change in haemaglobin

Question 21

What shape does the oxygen bindign curve for haemaglobin take?

Answer 21

Sigmoidal curve

Question 22

Why is the oxygen binding curve for haemaglobin sigmoidal?

Answer 22

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

Question 23

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

Answer 23

% saturation is more sensitive to smaller changes in pO2

Question 24

What is meant by co-operative binding of oxygen?

Answer 24

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

Question 25

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

Answer 25

Haemaglobin always in T state | binds less oxygen

Question 26

How is oxygen binding of haemaglobin regulated?

Answer 26

2,3-BPG Bohr effect

Question 27

Where is 2,3-BPG located?

Answer 27

In red blood cells | one molecule bound to one haemaglobin molecule

Question 28

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

Answer 28

Decreases affinity of haemaglobin for oxygen | binds less oxygen

Question 29

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

Answer 29

High altitude | to ensure more oxygen is released to tissues by haemaglobin

Question 30

What is the Bohr effect?

Answer 30

Refers to how binding of H+ and CO2 to haemaglobin | lowers its affinity for oxygen

Question 31

What is the advanage of the Bohr effect?

Answer 31

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

Question 32

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

Answer 32

Need higher pO2 for same % saturation | haemaglobin has a lower affinity for oxygen

Question 33

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

Answer 33

Need lower pO2 for same % saturation | haemaglobin has a higher affinity for oxygen

Question 34

What effect does carbon monoxide have on haemaglobin?

Answer 34

Binds more tightly to haemaglobin than oxygen does Causes other CO-free haemaglobin molecules to have higher affinity for oyxgen

Question 35

What are the consequences of carbon monoxide on oxygen transport?

Answer 35

Reduced oxygen release to tissues

Question 36

When is carbon monoxide fatal?

Answer 36

When it has bound to more than 50% of haemaglobin

Question 37

What is the quarternary structure of fetal haemaglobin?

Answer 37

Tetramer made up of: - two alpha globin chains - two gamma globin chains

Question 38

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

Answer 38

Fetal haemaglobin

Question 39

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

Answer 39

Fetal haemaglobin can extract oxygen from mother's blood

Question 40

What is the function of haemaglobin?

Answer 40

Transport oxygen and CO2 - pick up oxygen at lungs, release CO2 at lungs - pick up CO2 at tissues, release O2 at tissues