Lecture 4 DA Flashcards
What is the central dogma of protein folding?
All neccessary information for correct protein folding is contained within the primary sequence.
Selenium is toxic, how is it delivered?
As selenomethionine.
When molecular oxygen is reduced once, what does it become?
Superoxide anion radical.
When a superoxide anion radical is reduced once, what does it become?
Hydrogen proxide.
When hydrogen proxide is reduced once, what does it become?
Hydroxyl radical.
When a hydroxyl radical is reduced once, what does it become?
Water.
How many steps are needed to reduce molecular oxygen?
Molecular oxygen to hydrogen peroxide occurs in almost one step.
How many oxygen atoms do haemoglobin, haemocyanin and haemerythrin carry?
Haemoglobin - one per iron
Haemocyanin - one per two copper
Haemerythrin - one per two iron
In oxygen transport systems using iron, what is used to bind the iron? What is the benefit of this?
Poryphyrin ring is used, and allows the iron to change oxide states.
How does the iron in oxygen transport systems change oxide states?
The residue below the poryphyrin ring to push or pull electrons.
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?
Histidine is the residuebelow the poryphyrin ring.
It must be kept neutral, if it becomes basic, it will favour Fe3+, which is toxic.
What kind of curve does myoglobin affinity for oxygen have? What about haemoglobin?
Myoglobin - logarithmic
Haemoglobin - sigmoidal
What is positive and negative cooperativity? Which can be found in haemoglobin? How does it occur?
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.
In the deoxygenated form, how much does the Fe2+ ion lie out of plane in haemoglobin?
0.6A.
What happens to the Fe ion’s position in haemoglobin as it becomes oxygenated?
Gets pulled upward.
What is a consequence of the movement of the proximal histidine?
Results in a conformational change in the entire tetramer.
How does lower pH shift the haemoglobin-oxygen affinity curve?
To the right.
What is the Bohr effect?
Release of oxygen from haemoglobin due to lowered pH, which facilitates its release.
How many subunits does haemerythrin have, and what form of oxygen does it carry?
Its an octamer that carries a astable hydrogen peroxide.
What metal is found in haemocyanin?
Copper.
What state of haemoglobin does oxygen bind to?
To the tense state.
Which state of haemoglobin does a low pH favour?
Tense state.
What happens to haemoglobin when it is protonated (ie low pH)?
Becomes tense.
Is the tense state of haemoglobin oxygenated or deoxygenated? What aout the relaxed state?
Tense state is deoxygenated, relaxed is oxygenated.
