Question

please answer all :)

1. Suppose there is a mutation in the c subunit of ATP synthase, such that glutamate found in the middle of one of the membrane-spanning helices is converted to valine. What is likely to be the effect on ATP synthesis and why?

Inhibition of ATP synthesis. Because valine is hydrophobic, the a subunit will move in the reverse direction, causing hydrolysis, not synthesis, of ATP.

Inhibition of ATP synthesis. Valine cannot bind a proton, so there will be no proton flow through the inner membrane.

No effect. The middle of the helix is in contact with the hydrophobic center of the lipid bilayer, and valine is readily soluble in lipid.

Increase of ATP synthesis. Because the valine side chain is hydrophobic, the asubunit can move easily without regard for oxidative processes.

No effect. The valine side chain is shorter than the glutamate side chain, so it causes no change in the secondary structure of the helix.

2. What statement is incorrect about the mitochondrial ATP synthesizing complex?

It contains a transmembrane proton channel.

It contains a spherical headpiece called F1 located on the cytoplasmic side of the inner mitochondrial membrane.

It requires intact inner mitochondrial membranes to synthesize ATP.

The complex hydrolyzes ATP when the inner mitochondrial membranes are disrupted or leaky.

3. What coenzyme of the PDH complex functions as a "flexible swinging arm" when it transfers the reaction intermediate from one active site to the other?

lipoamide

thiamine pyrophosphate

coenzyme A

FAD

NAD+

4. What enzyme catalyzes the first redox reaction of the tricarboxylic acid cycle?

α-ketoglutarate dehydrogenase

isocitrate dehydrogenase

malate dehydrogenase

isocitrate lyase

pyruvate dehydrogenase

Answer 1

1. The mutation in the c subunit of ATPsynthase results in

Inhibition of ATP synthesis. Because valence cannot bind a proton , so there will be no proton flow.

ATP synthase is an ATP-generating enzyme that is dependent on proton movement down an electrochemical gradient. A Glutamate or Aspartate residue is present at the center of this membrane-spanning helices. Protons moves one at a time from exoplasmic medium by binding with the carboxylate side chain on glutamate residue. Valine is hydrophobic and it can not bind protons . So if there is no proton gradient then ATP synthesis will stop.

2.

ATP synthase contains 2 transmembrane proton half-channels.

so incorrect statement is It contains a transmembrane proton channel.

3.

lipoamide coenzyme oc the PDH complex function as a " flexible swinging arm" when it transfers the reaction intermediate from one active site to the other.

4.

Redox reaction is reduction-oxidation reaction. Oxidation state of an atom is changed in this reaction.

TCA cycle contains 4 redox reactions.

Isocitrate dehydrogenase enzyme catalyzes the first redox reaction in TCA cycle. It converts d-isocitrate to a-ketoglutarate and forms NADH by reducing NAD+.