Lecture 4 DA

Question 1

What is the central dogma of protein folding?

Answer 1

All neccessary information for correct protein folding is contained within the primary sequence.

Question 2

Selenium is toxic, how is it delivered?

Answer 2

As selenomethionine.

Question 3

When molecular oxygen is reduced once, what does it become?

Answer 3

Superoxide anion radical.

Question 4

When a superoxide anion radical is reduced once, what does it become?

Answer 4

Hydrogen proxide.

Question 5

When hydrogen proxide is reduced once, what does it become?

Answer 5

Hydroxyl radical.

Question 6

When a hydroxyl radical is reduced once, what does it become?

Answer 6

Water.

Question 7

How many steps are needed to reduce molecular oxygen?

Answer 7

Molecular oxygen to hydrogen peroxide occurs in almost one step.

Question 8

How many oxygen atoms do haemoglobin, haemocyanin and haemerythrin carry?

Answer 8

Haemoglobin - one per iron
Haemocyanin - one per two copper
Haemerythrin - one per two iron

Question 9

In oxygen transport systems using iron, what is used to bind the iron? What is the benefit of this?

Answer 9

Poryphyrin ring is used, and allows the iron to change oxide states.

Question 10

How does the iron in oxygen transport systems change oxide states?

Answer 10

The residue below the poryphyrin ring to push or pull electrons.

Question 11

What residue is used in haemoglobin to change the oxide state of the iron, and what charge must be kept on it? What will happen if it becomes too basic?

Answer 11

Histidine is the residuebelow the poryphyrin ring.

It must be kept neutral, if it becomes basic, it will favour Fe3+, which is toxic.

Question 12

What kind of curve does myoglobin affinity for oxygen have? What about haemoglobin?

Answer 12

Myoglobin - logarithmic

Haemoglobin - sigmoidal

Question 13

What is positive and negative cooperativity? Which can be found in haemoglobin? How does it occur?

Answer 13

Negative - If oxygen dissociates from one subunit, the other subunits will lose their oxygen quicker. Binding of oxygen induces change in shape.
Positive - If oxygen binds to a subunit, other subunits will gain oxygen more readily.

Question 14

In the deoxygenated form, how much does the Fe2+ ion lie out of plane in haemoglobin?

Answer 14

0.6A.

Question 15

What happens to the Fe ion’s position in haemoglobin as it becomes oxygenated?

Answer 15

Gets pulled upward.

Question 16

What is a consequence of the movement of the proximal histidine?

Answer 16

Results in a conformational change in the entire tetramer.

Question 17

How does lower pH shift the haemoglobin-oxygen affinity curve?

Answer 17

To the right.

Question 18

What is the Bohr effect?

Answer 18

Release of oxygen from haemoglobin due to lowered pH, which facilitates its release.

Question 19

How many subunits does haemerythrin have, and what form of oxygen does it carry?

Answer 19

Its an octamer that carries a astable hydrogen peroxide.

Question 20

What metal is found in haemocyanin?

Answer 20

Copper.

Question 21

What state of haemoglobin does oxygen bind to?

Answer 21

To the tense state.

Question 22

Which state of haemoglobin does a low pH favour?

Answer 22

Tense state.

Question 23

What happens to haemoglobin when it is protonated (ie low pH)?

Answer 23

Becomes tense.

Question 24

Is the tense state of haemoglobin oxygenated or deoxygenated? What aout the relaxed state?

Answer 24

Tense state is deoxygenated, relaxed is oxygenated.

Question 25

What effect does 2.6 bisphosphate have on haemoglobin, and how? What does it do to the affinity curve? When is it typically released for this purpose by the body?

Answer 25

It shifts the curve to the left, and facilitates oxygen uptake by haemoglobin. It does so allosterically, and resets its affinity for oxygen. Typically released at high altitudes as adaptation.