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Flashcards in Protein Function Deck (28):
1

How is oxygen transported around the body?

Oxygen binds to the Haem group on red blood cells
Binds to the Fe2+

2

How does the Fe bind to the Haem group?

Histidine Residue

3

What is Myoglobin's structure?

153 aa
compact
mainly Alpha helix
His 93 in 8th Alpha helix is covalently linked to Fe

4

What does binding of oxygen do to the Fe in myoglobin?

Moves from slightly below the plane of the ring to in the plane of ring changing the conformational shape

5

What does oxygen binding to myoglobin show?

A hyperbolic dependence on oxygen concentration

6

What are the features of haemoglobin structure?

2 polypeptide chains
2 alpha and 2 beta

7

What does oxygen binding to haemoglobin promote?

Stabilisation of the R state

8

What is the T state?

Low affinity state

9

What is the R state?

High affinity state

10

Why is the oxygen binding curve for haemoglobin sigmoidal?

Due to cooperative binding of oxygen as affinity increases as more oxygen molecules bind to the Hb subunit e.g. 1st O2- low affinity
4th O2- High affinity

11

What does cooperative binding mean for oxygen transport?

O2 can be efficiently carried from lungs to tissues and more sensitive to small change in O2 concentrations

12

What is BPG?

2,3- Biophosphoglycerate

13

What does BPG do?

Decreased the affinity for Oxygen

14

When does BPG concentration increase?

At high altitudes so O2 is released from tissues

15

What is the Bohr effect?

Binding of H+ and CO2 lowers the affinity for oxygen
Metabolically active tissues produce lots of H+ and CO2
this ensures delivery of O2 is coupled with demand

16

Why is CO poisonous?

Combines with Ferromyoglobin and Ferrohaemoglobin and blocks oxygen transport

17

How much more readily for CO bind to Haemoglobin than O2?

250x

18

When would CO levels become fatal?

When COHb is more than 50%

19

What does CO binding to for unaffected subunits?

increase affinity for oxygen

20

What is the different between Adult and Foetal Haemoglobin?

Adult contains 2 alpha and 2 beta
Foetal contains 2 alpha and 2 gamma

21

Why is Foetal haemoglobin so important?

Allows transfer of oxygen to Foetus from the mother due to higher affinity

22

What is the mutation in Sickle Cell anaemia?

Glutamate to Valine in Beta Globin

23

Why does the Sickle cell mutation cause a problem?

Sticky hydrophobic posted form by the Valine which allow deoxygenated HbS to polymerize causing sickle shape- prone to anaemia and more rigid so cause blockages

24

What is Thalassaemia?

Inbalance between number of alpha and beta chains

25

What is a- Thalassaemia?

decreased or absent alpha globin chain
shows before birth
Beta chains can form stable tetramers with increased affinity for oxygen

26

What is B- Thalassaemia?

Decreased or absent beta globin chains
alpha chains cannot form stable tetramers
shows after birth

27

What do activators do to the curve?

Shift to left and enhance high affinity R state

28

What do allosteric inhibitors do to the curve?

Shift to the right and enhance low affinity T state