AAMC Scored FL 1 and 2 (spoilers) questions

[itsalwayssunny96]

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I know I have a lot of questions, so any input at all would be greatly appreciated 🙂 I included most of them here!

B/B #19
So while thinking about whether to pick choice C or D, I ruled out D because I thought that it wasn't right to assume what type of solution Figure 2 took place in. But the explanation basically says that we did have to assume that. There is no mentioning of it throughout the entire passage. How did you reason that it was talking about an aqueous solution?

B/B #20
I was lost on this one (and would like for someone to explain their reasoning), but for even if the proton gradient dissipated, the ETC could still work? As far as making H2O with O2 as the final electron acceptor? I.e. the proton gradient being dissipated wouldn't change the fact that electrons could still be transported. I still don't get how the proton gradient would be dissipated though.

P/S #51
What nutrients are transported by axons...? Ions..? I do understand how choice A is correct but just didn't know B was something that occurred?

C/P #19
So, I just want to make sure my reasoning for this one is correct. Since it says spHM we know that an amino acid has to be phosphorylated and out of the FLGFTY sequence, the only 2 that could potentially be phosphorylated are threonine and tyrosine. But in the answer choices all you are really looking for is an amino acid sequence that similar to threonine can be phosphorylated right? My only problem with the explanation is that it says that the charge stays the same but at pH of 7 (which is safe to assume), glutamate (E) has a -1 charge ...and glutamine (Q) is neutral, no? Or is it just trying to say after being phosphorylated, the threonine and glutamate are both the same charge (since a phosphate adds a -2 charge)? Sorry for the long rant on this question.

C/P #33
Confused with one part of their explanation - how does the favorability of the reaction decrease with temperature? Where did they get that from the passage?

C/P #49
Their math in the explanation confused the hell out of me? Just wanted to make sure I solved it correctly. I just did Hf = sum of products in moles x their standard enthalpies - sum of reactants in moles x their standard enthalpies. I got the correct answer but I just wanted to try to make sense of AAMC's answer

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[aldol16]

I was lost on this one (and would like for someone to explain their reasoning), but for even if the proton gradient dissipated, the ETC could still work? As far as making H2O with O2 as the final electron acceptor? I.e. the proton gradient being dissipated wouldn't change the fact that electrons could still be transported. I still don't get how the proton gradient would be dissipated though.

Well, the protein obviously pokes holes in membranes, which is what causes dyes that were previously contained within liposomes to leak out and what would cause the proton gradient to dissipate. The analogy people often use to describe the proton pump is like a pump that pumps water out of your basement. In that case, what protein X would do would be to poke a hole in the wall somewhere so that the water that's being pumped out has a way to flow back into the basement. That doesn't mean the pump (electron transport chain) stops working - just that the gradient no longer builds up.

Confused with one part of their explanation - how does the favorability of the reaction decrease with temperature? Where did they get that from the passage?

They must be talking about a thermodynamic phenomenon here because reaction kinetics are always accelerated by increased temperature. You didn't post the entire passage here so I don't know what the question is or what the thermodynamics of the reaction is, but if you know that a certain reaction is, say, exothermic, then it would be disfavored by high temperatures because since heat is generated by the system, the addition of heat (high temperature) would drive the reaction to the left, or towards the reactants and you would end up with a distribution that favored the reactants (assuming reversibility).

Their math in the explanation confused the hell out of me? Just wanted to make sure I solved it correctly. I just did Hf = sum of products in moles x their standard enthalpies - sum of reactants in moles x their standard enthalpies. I got the correct answer but I just wanted to try to make sense of AAMC's answer

That is the correct equation and if you got the correct answer, then you did it right. I agree - their equation is convoluted.

So while thinking about whether to pick choice C or D, I ruled out D because I thought that it wasn't right to assume what type of solution Figure 2 took place in. But the explanation basically says that we did have to assume that. There is no mentioning of it throughout the entire passage. How did you reason that it was talking about an aqueous solution?

When you're working with proteins, you're always in aqueous solution. Proteins crash out in organics - proteins are in biological systems, which, to the best of our knowledge about all existing lifeforms, are based on aqueous solutions.

So, I just want to make sure my reasoning for this one is correct. Since it says spHM we know that an amino acid has to be phosphorylated and out of the FLGFTY sequence, the only 2 that could potentially be phosphorylated are threonine and tyrosine. But in the answer choices all you are really looking for is an amino acid sequence that similar to threonine can be phosphorylated right? My only problem with the explanation is that it says that the charge stays the same but at pH of 7 (which is safe to assume), glutamate (E) has a -1 charge ...and glutamine (Q) is neutral, no? Or is it just trying to say after being phosphorylated, the threonine and glutamate are both the same charge (since a phosphate adds a -2 charge)? Sorry for the long rant on this question.

I don't see this one posted. As a general rule, if you're posting a screenshot and asking a question about a figure or the passage or a question or answer explanation, make sure to have all the relevant parts posted (i.e. if you're asking about an answer explanation, you should have the answer explanation there and the relevant parts in the passage it refers to) or else it's hard for people to help you. It takes more work on their part to go through and actually look up the questions and so most people won't do that.

 

[itsalwayssunny96]

I don't see this one posted. As a general rule, if you're posting a screenshot and asking a question about a figure or the passage or a question or answer explanation, make sure to have all the relevant parts posted (i.e. if you're asking about an answer explanation, you should have the answer explanation there and the relevant parts in the passage it refers to) or else it's hard for people to help you. It takes more work on their part to go through and actually look up the questions and so most people won't do that.

I know, it wouldn't let me include more than 5 images lol, but I just took down number 49 and uploaded the picture for this particular question. Thanks for clarifying for the other questions though - that helped.

 

[aldol16]

I know, it wouldn't let me include more than 5 images lol, but I just took down number 49 and uploaded the picture for this particular question. Thanks for clarifying for the other questions though - that helped.

Still can't see the answer explanation that you're referring to.

 

[itsalwayssunny96]

Still can't see the answer explanation that you're referring to.

The full explanation for number 19 says:
The answer to this question is D because the phosphorylated threonine would most likely be mimicked by glutamic acid in terms of size and charge.

That's all it says.

 

[aldol16]

The answer to this question is D because the phosphorylated threonine would most likely be mimicked by glutamic acid in terms of size and charge.

You're supposed to compare glutamate to phosphorylated threonine. If you do that, you'll see that they are structurally very similar. With respect to charge, that's debatable. Glutamate obviously has a -1 charge on its side chain. Phosphorylated threonine has either a -1 or -2 charge, since the second pKa of phosphate is around 7 and so at physiological pH, you'd expect significant quantities of mono-deprotonated phosphate and di-deprotonated phosphate.

 

[carterjt47]

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I know I have a lot of questions, so any input at all would be greatly appreciated 🙂 I included most of them here!

B/B #19
So while thinking about whether to pick choice C or D, I ruled out D because I thought that it wasn't right to assume what type of solution Figure 2 took place in. But the explanation basically says that we did have to assume that. There is no mentioning of it throughout the entire passage. How did you reason that it was talking about an aqueous solution?

B/B #20
I was lost on this one (and would like for someone to explain their reasoning), but for even if the proton gradient dissipated, the ETC could still work? As far as making H2O with O2 as the final electron acceptor? I.e. the proton gradient being dissipated wouldn't change the fact that electrons could still be transported. I still don't get how the proton gradient would be dissipated though.

P/S #51
What nutrients are transported by axons...? Ions..? I do understand how choice A is correct but just didn't know B was something that occurred?

C/P #19
So, I just want to make sure my reasoning for this one is correct. Since it says spHM we know that an amino acid has to be phosphorylated and out of the FLGFTY sequence, the only 2 that could potentially be phosphorylated are threonine and tyrosine. But in the answer choices all you are really looking for is an amino acid sequence that similar to threonine can be phosphorylated right? My only problem with the explanation is that it says that the charge stays the same but at pH of 7 (which is safe to assume), glutamate (E) has a -1 charge ...and glutamine (Q) is neutral, no? Or is it just trying to say after being phosphorylated, the threonine and glutamate are both the same charge (since a phosphate adds a -2 charge)? Sorry for the long rant on this question.

C/P #33
Confused with one part of their explanation - how does the favorability of the reaction decrease with temperature? Where did they get that from the passage?

C/P #49
Their math in the explanation confused the hell out of me? Just wanted to make sure I solved it correctly. I just did Hf = sum of products in moles x their standard enthalpies - sum of reactants in moles x their standard enthalpies. I got the correct answer but I just wanted to try to make sense of AAMC's answer

Why are these questions considered spoilers?. Will the same test questions appear word for word when someone buys the full length practice test(FL1 and FL2) from the AAMC?