5. What is the function of selectivity filter amino acids in an ion channel? The

Question

5. What is the function of selectivity filter amino acids in an ion channel?

They close the channel pore after ion passage.

They determine the preference for a particular ion.

They limit the number of ions passing through the channel.

All of the above.

None of the above

Which of the following does not pump protons?

Complex I            

Complex II

Complex III

Complex IV

All of the above.

7. Fructose can cyclize to (a)

pyranose ring.

furanose ring

both pyranose and furanose ring forms.

All of the above.

None of the above.

They close the channel pore after ion passage.

They determine the preference for a particular ion.

They limit the number of ions passing through the channel.

All of the above.

None of the above

Explanation / Answer

1.

ion channels are selectively permeable i.e, they allow ions of certain charge or size to pass through. these are channels that allow down hill transport that is based on concentration and no energy required. they determine the preference for a particular ion. they limit the number of ions passing through, because, the transport is governed by concentration and membrane potential differences. if the concentration and membrane potential are in equillibrium, that limits the passage of the resective ions. some ion channels such as ligand gated ion channels or voltage gated ion channels open and close based on the binding of ligand or membrane potential.

C. all of the above.

2.

complex I (NADH dehydrogenase) pumps 4 protons.

complex II (succinate dehydrogenase) do not pump any electrons.

complex III (cytochrome bc complex) pumps 2 protons.

complex IV (cytochrome c oxidase) pumps 4 protons per cycle.

B. complex II

3. in solution, fructose exists as 70 % fructopyranose and 22% fructofuranose and small amounts of other forms. therefore it can be cyclize to both the forms.

C. both pyranose and furanose forms

or

D. All of the above

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