NS3 CP #52 BB #27

[br2pi5]

Hello! I don't think I've done many elasticity questions in prep for my MCAT hence why this confused me so much, any help appreciated!! Also for #27 (bio/biochem), is this something we have to memorize, what the graph should look like under different order kinetics?

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[NextStepTutor_1]

Hi @br2pi5 -

The C/P question draws on the fact that PE = 1/2 kx^2 in springs is testable content, and additionally links it to conservation of energy. We can't use PE = 1/2 kx^2 to answer this question directly, though, because we're not given k, so the key here is to recognize that gravitational potential energy is being converted into energy stored in the spring (elastic potential energy). This is conceptually similar to questions where KE(i) + PE(i) = KE(f) + PE(f) is used to predict the final velocity of an object dropped from a certain height, but with PE(spring) instead of KE.

Re: the B/B question, to some extent this is a question of preference. Personally I would suggest approaching this through understanding rather than memorizing, because the definition of different order kinetics can be used pretty directly to predict the shape of the graph. Based on the answer choice of third-order that you picked, is it possible that the issue w/ this question was the need to focus on the initial segment of the graph?

Thanks as always for the questions, and I hope this helps demystify these topics a bit! 🙂

 

[br2pi5]

@NextStepTutor_1 may I ask you as well for this NS4 C/P question, how do we know what the units of the ratio shown in the table are? not knowing the units I had trouble figuring out what to divide and what to multiply etc

Also for NS4 C/P #25, how do you know what is the IC50 of compound 4a (ZSTK474) in order to compare with the cell lines if there was an increase or decrease?

 

[NextStepTutor_1]

Hi @br2pi5 -

For the table (in passage 1), the fact that they describe it as a ratio suggests that it is a unitless number. This is not true for all ratios, but it is true for ratios where you divide two values with the same units, which is a common way of coming up with analytically useful ratios. The fact that it's described as a "solubility enhancement" ratio suggests that it's an indication of how much the solubility shown in each row of the table is increased compared to some baseline. In Q3, which asks about this directly, we can eliminate A and B immediately because we're given no information about what the "hydrophobic solubility" of A would even mean, and then we can eliminate D because a ratio must involve dividing something -- so we can get away with only having a very general sense of how it's defined. However, we could also do some math to confirm that it's defined as the observed solubility of A in some MH solution divided by the baseline solubility of A in water, which gives us a measure of how much a certain MH solution increases the solubility of A.

For Q25, each cell in Table 1 contains an IC50 value in units of uM. Each of those values is specific for a certain compound (4a, 4b, 4c, 5a, or 5b) and a certain cell line (H1975, A549, or HCT116). Therefore, we can read down the table to determine how cytotoxic the compounds were for a given cell line, or read across to see how cytotoxic a certain compound was across various cell lines. That serves as the basis of comparison for Q25.

Hope this helps clarify these questions!

 

[br2pi5]

Hi @br2pi5 -

For the table (in passage 1), the fact that they describe it as a ratio suggests that it is a unitless number. This is not true for all ratios, but it is true for ratios where you divide two values with the same units, which is a common way of coming up with analytically useful ratios. The fact that it's described as a "solubility enhancement" ratio suggests that it's an indication of how much the solubility shown in each row of the table is increased compared to some baseline. In Q3, which asks about this directly, we can eliminate A and B immediately because we're given no information about what the "hydrophobic solubility" of A would even mean, and then we can eliminate D because a ratio must involve dividing something -- so we can get away with only having a very general sense of how it's defined. However, we could also do some math to confirm that it's defined as the observed solubility of A in some MH solution divided by the baseline solubility of A in water, which gives us a measure of how much a certain MH solution increases the solubility of A.

For Q25, each cell in Table 1 contains an IC50 value in units of uM. Each of those values is specific for a certain compound (4a, 4b, 4c, 5a, or 5b) and a certain cell line (H1975, A549, or HCT116). Therefore, we can read down the table to determine how cytotoxic the compounds were for a given cell line, or read across to see how cytotoxic a certain compound was across various cell lines. That serves as the basis of comparison for Q25.

Hope this helps clarify these questions!

thank you so much! you're always so helpful!

 

[NextStepTutor_1]

thank you so much! you're always so helpful!

You're very welcome!