How detailed do I have to memorize bio/biochem?

[PopeKnope23]

Hey guys.. kind of a weird question, but as I'm going through a lot of the bio/biochem pathways, I'm wondering just how detailed I need to get with my memorization. For example, the citric acid cycle. I of course need to know the overall goal is to oxidize acetyl-CoA to CO2 and generate NADH, FADH2, and GTP. However, do I need to know every single enzyme that's used and in what order? Is there a good resource that simplifies the details and is reliable enough for MCAT prep? (oxidative phosphorylation, gluconeogenesis, etc)

Thanks in advance!

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[esob]

I had a question on the AAMC section bank today that expected you to be able to recognize the skeletal structural formulas for succinate and malate and to then realize that fumarate was the intermediate between them in the citric acid cycle. I had another that required you to know all the enzymes and their products in the pentose phosphate pathway.

 

[aldol16]

I had a question on the AAMC section bank today that expected you to be able to recognize the skeletal structural formulas for succinate and malate and to then realize that fumarate was the intermediate between them in the citric acid cycle. I had another that required you to know all the enzymes and their products in the pentose phosphate pathway.

Did it give you all of their chemical structures? Because if it did, then you wouldn't need to memorize per se as much as understand chemical logic. That is, you know that to get from a saturated structure to a hydroxyl group (oxidized carbon) you have to desaturate, or oxidize, the compound (unless you're doing direct C-H activation which the MCAT would not expect you to understand). So making a double bond is one way of desaturation. Generally, nature desaturates compounds via making double bonds. From there, you can do all sorts of addition reactions to functionalize things further. It's just that completely saturated molecules are extremely hard to work with chemically.

 

[aldol16]

I wouldn't worry so much with memorizing as much as understanding. Understand the chemistry and chemical logic behind each step and the pathways should come easier to you. Sit down and draw out the reaction pathways if you have to. You'll find that the names of the enzymes often tell you what they do (or the reverse of what they do). For example, GAPDH unsurprisingly dehydrogenates (or oxidizes) GAP. Note that in all reversible reactions, the enzyme also catalyzes the reaction in the reverse reaction - whether forward or reverse dominates depends on the relative concentrations of reactants/products.

 

[PopeKnope23]

Thank you! I have yet to get to all the pathways in my biochem class, so I just wanted to have the right mindset when learning them. I'll be sure to understand rather than memorize.

 

[esob]

Did it give you all of their chemical structures? Because if it did, then you wouldn't need to memorize per se as much as understand chemical logic. That is, you know that to get from a saturated structure to a hydroxyl group (oxidized carbon) you have to desaturate, or oxidize, the compound (unless you're doing direct C-H activation which the MCAT would not expect you to understand). So making a double bond is one way of desaturation. Generally, nature desaturates compounds via making double bonds. From there, you can do all sorts of addition reactions to functionalize things further. It's just that completely saturated molecules are extremely hard to work with chemically.

The question basically asked, what is the compound between Succinate and Malate, but instead of giving you the nomenclature, they simply gave you the chemical structures. Thus, solving the problem involved not only knowing the order of the krebs cycle, but also knowing at least the skeleton structure of either succinate or malate, or preferably both.

 

[aldol16]

The question basically asked, what is the compound between Succinate and Malate, but instead of giving you the nomenclature, they simply gave you the chemical structures. Thus, solving the problem involved not only knowing the order of the krebs cycle, but also knowing at least the skeleton structure of either succinate or malate, or preferably both.

Yes, but was the answer choice in chemical structure or named form?

 

[esob]

Yes, but was the answer choice in chemical structure or named form?

named. So the answer was fumarate but in order to get to that answer you needed to be able to recognize at least one of the skeleton models presented.

 

[curvesetter]

Hey guys.. kind of a weird question, but as I'm going through a lot of the bio/biochem pathways, I'm wondering just how detailed I need to get with my memorization. For example, the citric acid cycle. I of course need to know the overall goal is to oxidize acetyl-CoA to CO2 and generate NADH, FADH2, and GTP. However, do I need to know every single enzyme that's used and in what order? Is there a good resource that simplifies the details and is reliable enough for MCAT prep? (oxidative phosphorylation, gluconeogenesis, etc)

Thanks in advance!

At the very, very least you should know all the irreversible/regulated steps and what the positive/negative regulators of that step are.

 

[NextStepTutor_1]

Hi @PopeKnope98 -

Can details like that be tested? Yes. I think that SB question shows that to be the case. Are they likely to be tested? Not especially. More to the point, given the finite amount of time we all have, is it a good use of your time to focus super small-scale details? For most MCAT students, keeping in mind that by definition the < 510 range by definition includes the vast majority of students, almost certainly not. As always, it's a question of prioritization. One of the reasons why you commonly hear advice to focus on logic and mechanisms is because insights in those domains can pay off on multiple questions (& even on passage reading/comprehension), whereas knowing by heart (for example), the specific structures of succinate, fumarate, and malate will at best pay off on one question, and at that the odds are not very high. So I think it depends on where you're at -- if you're making good progress with practice materials, and you don't have any other areas of content that need major review (using the AAMC content outline to self-assess can be helpful), then it could make sense to hone in on this level of detail, but I wouldn't generally recommend it unless everything else is on point in your studying.

Hope this helps provide some insight into the situation!

 

[westsidestoryz]

Recognizing the enzymes that regulate allosteric regulation, rate limiting enzymes and inhibitory enzymes would come in handy. I would memorize the citric acid cycle using mnemonics as well as glycolysis enzymes. I’m just saying this because i saw couple questions on it and it’s free points if you can recall it.

 

[PopeKnope23]

Hi @PopeKnope98 -

Can details like that be tested? Yes. I think that SB question shows that to be the case. Are they likely to be tested? Not especially. More to the point, given the finite amount of time we all have, is it a good use of your time to focus super small-scale details? For most MCAT students, keeping in mind that by definition the < 510 range by definition includes the vast majority of students, almost certainly not. As always, it's a question of prioritization. One of the reasons why you commonly hear advice to focus on logic and mechanisms is because insights in those domains can pay off on multiple questions (& even on passage reading/comprehension), whereas knowing by heart (for example), the specific structures of succinate, fumarate, and malate will at best pay off on one question, and at that the odds are not very high. So I think it depends on where you're at -- if you're making good progress with practice materials, and you don't have any other areas of content that need major review (using the AAMC content outline to self-assess can be helpful), then it could make sense to hone in on this level of detail, but I wouldn't generally recommend it unless everything else is on point in your studying.

Hope this helps provide some insight into the situation!

This is very helpful, thank you so much! I honestly have a lot of content yet to cover (my MCAT is May 19). I have yet to look over any of those pathways and enzymes because we haven't covered them in my biochem class. I sure hope they aren't too complex to learn because I'm a little nervous!

 

[NextStepTutor_1]

Hi @PopeKnope98 -

With only about 6 weeks to go, I'd suggest taking the bull by the horns and at least starting to review these topics before you cover them in a biochem class. The next time you have an hour or so of free time, pick one of the big four pathways for the MCAT (glycolysis, citric acid cycle, electron transport chain, and [arguably] beta oxidation), consult whichever review books you're using, Wikipedia, Khan Academy, or even your biochem textbook (although you'd need to avoid drowning in detail there) and try to answer the following questions:

1. Who cares? What's the point of this pathway in the body?
2. What goes in and what comes out?
3. What happens to the products? (This should link up to the "who cares?" question)
4. Where does it happen?
5. Under what conditions is this pathway favored/disfavored?

There's more to learn about every pathway—and I definitely agree with the advice that others have provided about learning committed/regulatory steps and enzymes—but these questions should be relatively quick to answer and will at least demystify the topics and give you a framework for studying the details.

Before drowning in the details, remember that the point of these pathways is to get energy in the form of ATP/GTP (in the context of aerobic metabolism). There are three basic ways to do this: (1) directly making it (aka substrate-level phosphorylation), (2) producing the electron carriers NADH and FADH2, which go to the electron transport chain to ultimately power ATP synthase, or (3) producing some compound that itself gets fed into another pathway that results in (1) or (2). Keeping in mind that energy-producing pathways always work towards one of these three goals can help understand the logic of the steps.

 

[PopeKnope23]

Hi @PopeKnope98 -

With only about 6 weeks to go, I'd suggest taking the bull by the horns and at least starting to review these topics before you cover them in a biochem class. The next time you have an hour or so of free time, pick one of the big four pathways for the MCAT (glycolysis, citric acid cycle, electron transport chain, and [arguably] beta oxidation), consult whichever review books you're using, Wikipedia, Khan Academy, or even your biochem textbook (although you'd need to avoid drowning in detail there) and try to answer the following questions:

1. Who cares? What's the point of this pathway in the body?
2. What goes in and what comes out?
3. What happens to the products? (This should link up to the "who cares?" question)
4. Where does it happen?
5. Under what conditions is this pathway favored/disfavored?

There's more to learn about every pathway—and I definitely agree with the advice that others have provided about learning committed/regulatory steps and enzymes—but these questions should be relatively quick to answer and will at least demystify the topics and give you a framework for studying the details.

Before drowning in the details, remember that the point of these pathways is to get energy in the form of ATP/GTP (in the context of aerobic metabolism). There are three basic ways to do this: (1) directly making it (aka substrate-level phosphorylation), (2) producing the electron carriers NADH and FADH2, which go to the electron transport chain to ultimately power ATP synthase, or (3) producing some compound that itself gets fed into another pathway that results in (1) or (2). Keeping in mind that energy-producing pathways always work towards one of these three goals can help understand the logic of the steps.

Thank you so much! This kind of guidance is EXACTLY what I needed! I’m setting aside 3 hours of purely MCAT studying tonight, so I will begin asap. I appreciate all your help 🙂

 

[NextStepTutor_1]

Thank you so much! This kind of guidance is EXACTLY what I needed! I’m setting aside 3 hours of purely MCAT studying tonight, so I will begin asap. I appreciate all your help 🙂

Of course!! Very glad to be of help 🙂

 

[LukaDoncicLuk]

Dont forgot gluconeogenesis. You should know at the least the rate limiting step, what the point of the process, what hormones/energy levels favor it, why muscle and liver cells use it differently etc.

 

[NextStepTutor_1]

Dont forgot gluconeogenesis. You should know at the least the rate limiting step, what the point of the process, what hormones/energy levels favor it, why muscle and liver cells use it differently etc.

Yes, absolutely! Gluconeogenesis is a must, as are glycogenogenesis and glycogenolysis (i.e. glycogen formation and breakdown). My personal sense, though, is that it's a lot easier to study those processes once you have glycolysis down. The pentose phosphate pathway should also be on the list.

 

[LukaDoncicLuk]

Yes, absolutely! Gluconeogenesis is a must, as are glycogenogenesis and glycogenolysis (i.e. glycogen formation and breakdown). My personal sense, though, is that it's a lot easier to study those processes once you have glycolysis down. The pentose phosphate pathway should also be on the list.

I would know a lot less of the detail for these pathways but they are still important. Mostly just know the key enzymes/products and when/where these processes take place.

 

[PopeKnope23]

Thanks for all your help everyone! 🙂