Is my answer to this respiration question correct ?

JacobBob

10

I’ll insert a picture of the question and my answer
And the mark schemes answer

Reply 1

JacobBob

OP

10

I wanna know if the thing about more NADH is correct because I based my answer off of that and I found a few shared points but nothing about NADH in the mark scheme
Also, I want to know how i should include cristae in my answer

Reply 2

phoebeg76

12

So the question is about increasing surface area of the membranes inside the mitochondria. The inside bit is important, as the cristae are the partitions inside the mitochondria formed by the inner membrane. This is where oxidative phosphorylation occurs, so a larger surface area of the membranes surrounding the cristae will increase oxidative phosphorylation. You've mentioned cristae in your answer, and that's probably enough for A-Level as the mark scheme only asks for a reference to cristae, not for an explanation of it.

Referencing the ATPase by name would help as well, you've mentioned what it does which is great, but A-Levels are purely about playing the game and saying the right words. Although saying that you have mentioned chemiosmosis so that covers point 7 in the mark scheme!

I think its a great answer to be honest, you've said everything the mark scheme wants you to.

It's been a few years since I did A-Levels, and I know study Biology at uni, so your answer doesn't seem really detailed to me, but that's A-Level! All about knowing the mark schemes through and through, and all about saying the right words and playing the game!

Good luck with exams this year, you'll do great.

Reply 3

Jpw1097

19

Original post by JacobBob

I wanna know if the thing about more NADH is correct because I based my answer off of that and I found a few shared points but nothing about NADH in the mark scheme
Also, I want to know how i should include cristae in my answer

You've mentioned the cristae, and the H⁺ (proton) gradient across the inner mitochondrial membrane and the idea of chemiosmosis. However, you mention that the increase in surface area of the mitochondria will lead to increased NADH production in the Krebs cycle. However, the point it's getting at is that there is a greater surface area and therefore there will be more electron carriers and transporters in the membrane. More electron carriers/transporters = more electron transport chain = more protons pumped from the matrix to the intermembrane space = more protons flowing back into the matrix down their electrochemical gradient using ATP synthase = more oxidative phosphorylation = more ATP produced.

Reply 4

JacobBob

OP

10

Original post by Jpw1097

You've mentioned the cristae, and the H⁺ (proton) gradient across the inner mitochondrial membrane and the idea of chemiosmosis. However, you mention that the increase in surface area of the mitochondria will lead to increased NADH production in the Krebs cycle. However, the point it's getting at is that there is a greater surface area and therefore there will be more electron carriers and transporters in the membrane. More electron carriers/transporters = more electron transport chain = more protons pumped from the matrix to the intermembrane space = more protons flowing back into the matrix down their electrochemical gradient using ATP synthase = more oxidative phosphorylation = more ATP produced.

Alright, I understood what I have to write and why but just for the knowledge, the NADH thing, is it wrong ?

Reply 5

Jpw1097

19

Original post by JacobBob

Alright, I understood what I have to write and why but just for the knowledge, the NADH thing, is it wrong ?

In your answer, you mention that more NADH would be made in the Krebs cycle. Increasing the surface area of the mitochondrial membranes wouldn't really increase the amount of NADH produced. The question is more asking about how increasing the surface area will increase the number of electron transporters and therefore lead to more oxidative phosphorylation. Remember that the Krebs cycle occurs within the mitochondrial matrix, and the question specifically asks about the membranes. So more NADH isn't produced, however, you could argue that more NADH will be used up per unit time as the energy from NADH (and FADH₂) is used to drive the proton pumps in the electron transport chain. Hope that makes sense.

Is my answer to this respiration question correct ?

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