AAMC CBT3 and 3R OFFICIAL Q&A

[Vihsadas]

This is the official Q&A thread for AAMC CBT3 and 3R.

Please post ONLY questions pertaining to AAMC CBT3 and 3R.
Out of respect for people who may not have completed the other exams, do not post questions or material from any other AAMC exam.

Please see this thread for the rules of order before you post.

Good luck on your MCAT!

---

Members don't see this ad.

 

[linusp]

On CBT 24 in PS, how am i supposed to know that the 2nd harmonic is 200hz? Does that mean the 3rd harmonic is 300hz? I feel like this is an easy question that I should know how to do.

I was wondering this too, but my reasoning behind my answer was that of the provided answer choices, only one had a smaller period (and thus higher freq) than the 100Hz first harmonic. That choice was choice A.

I had another question, a bit more conceptual:

For the HC Disease passage P2 of the BS, the final question #106 gives an answer that the strongest support for it being a genetic disease is

B. That there is no significant difference in dietary habits between the affected and unaffected families.

whereas I chose

C. HC appears to be caused by a malfunction at the plasma membrane.

Shouldn't this be stronger evidence? Given that the passage states that it has to do with a membrane receptor protein, isn't this the strongest link to it being a genetic disorder?

Thanks!

 

[LaurenMCAT]

For the HC Disease passage P2 of the BS, the final question #106 gives an answer that the strongest support for it being a genetic disease is

B. That there is no significant difference in dietary habits between the affected and unaffected families.

whereas I chose

C. HC appears to be caused by a malfunction at the plasma membrane.

Shouldn't this be stronger evidence? Given that the passage states that it has to do with a membrane receptor protein, isn't this the strongest link to it being a genetic disorder?

The answer MUST reflect either the inheritability of the disease and not its "happenstance" development OR show that all else being equal, environment cannot account for the disease. In other words, if we compare environmental and behavioral factors and there is no difference, yet some families show the disease and others don't, then the env./beh. cannot account for this.

In fact, we see in P3 that affected/unaffected families have no difference in diet.

Of the possible answer choices, we can eliminate A, C, D:
A) doesn't differentiate genetics vs. environmental causes. could be either.
C) could be due to genetics or not (poisons, hormonal release, diet can affect membrane integrity, etc.)
D) again, doesn't indicate whether this is genetic or due to environmental factors

So...we're left with B 👍

 

[LaurenMCAT]

Can someone explain the answer to this question to me? It is about selective precipitation but i dont understand how the sequence in which the Pb2+ was precipipated in the passage can be extrapolated to deduce the solubilities of the different anions with Pb2+

When a compound precipitates in relation to another compound is dependent upon their different solubilities (Ksp).

Theoretically, if Compound A has a Ksp < Compound B, we can say any of the following:
Compound A is less likely to dissolve than Compound B
Compound B is more soluble than A
Compound A is less soluble than B
Compound B is more likely to dissolve than A

In this question, we have three anions to compare:
SO4 2-
CO3 2-
I -
and the question asks us to find which is least soluble (listed first).

From the passage, we can deduce the following:
Compound A is PbSO4
Some of PbSO4 dissolves to form PbI2
All of PbI2 dissolves to form PbCO3

Overall, we would say that PbCO3 is most tightly bound, has the smallest Ksp, compared to the other two compounds. Then, its a close call between PbSO4 and PbI2. 🙂

So, when looking at our answer choices, we realize that we don't have enough info to say A is true, and C and D have CO3 2- in the wrong place.

Cool? 😎

 

[Medgen]

Can anyone explain how a resonance structure can exist in which the oxygen double bonds to the nitrogen in HNO3? The question asks which bond is the shortest and gives as a rationale the N-O bond (as opposed to the N-OH bond) because it can form a resonance structure in which it double bonds to the nitrogen... but I don't see it.

 

[mgpenguin]

http://en.wikipedia.org/wiki/Nitric_acid

When you draw the Lewis structure you will see that there is a double bond between the N and one of the oxygens... and that since both oxygens are the same it is delocalized across both.

 

[chiapet874]

I had a question on #38 which asks what will happen to post-menopausal women receiving estrogen/progesterone therapies.

The answer is: periodic menstruation will occur.

How can this be? After the LH spike in women who are pre-menopausal, levels of estrogen and progesterone spike up to inhibit LH- this is important because it prevents the development of future follicles if the egg is successfully fertilized (which is why the corpus leuteum and placenta both produce these two hormones till term)

So if you were to give a women these hormones, their menstruation should stop shouldn't it?

 

[Hexon]

i have a LOT of questions lol; ok, first the PS section:


24) how do you know the 2nd harmonic has an f of 200hz??

38) i don't understand how the recoil speed is (4/222)1.5 x 10^7 m/s=2.7x10^5

41)which optics eqn does this q ask for? i still don't understand how it can be 4f/4/3f.

50) how the heck can it be determined that bond b is the longest??!! i don't even understand the answer.

thanks for your help guys and hals🙂

 

[dmplz707]

Hey guys so I just took AAMC 3R and got a 28 10/8/10. I was pretty demoralized after doing the VR section of this test and the score reflects just that 🙁 . I don't even know the heck I got an 8...I seriously felt like I was guessing on most of those passages.

I seriously couldn't understand what the heck I was reading. I remember reading that wolf passage and thinking to myself this isn't so bad. Then I get to the questions and I'm just like...my goodness I take that back. Then the worst of the worst came when I hit that Confucius passage and then I was just like WTF have I been learning in my English classes throughout my primary education?

Emotions aside, I was wondering if someone could please give me their own interpretation/explanation on questions 59, 60 and 62 on the Wolf passage of the VR section of AAMC 3R. I can't even understand the answer explanations that were even provided. Thanks a lot guys.

 

[bullsfan1986]

i have a LOT of questions lol; ok, first the PS section:


24) how do you know the 2nd harmonic has an f of 200hz??

38) i don't understand how the recoil speed is (4/222)1.5 x 10^7 m/s=2.7x10^5

41)which optics eqn does this q ask for? i still don't understand how it can be 4f/4/3f.

50) how the heck can it be determined that bond b is the longest??!! i don't even understand the answer.

thanks for your help guys and hals🙂

24) For questions like these you really don't need to know what the frequency of the 2nd harmonic is. All you need to know is that the second harmonic will always have a greater frequency than the first harmonic. Because f=1/T, something with a greater frequency will have a smaller period. Knowing this, (and also knowing that the period of the first harmonic is 1/100=0.01 seconds) you know that your answer has to be less than 0.01 seconds. Thus, the only answer choice that remains is A.

38) You can take the clue from the question when it says to assume that the momentum of the gamma particle is negligible to the alpha particle. This means that when the decomposition reaction happens and the alpha particle (m=4g/mol) breaks off of Radium (m=226g/mol) in order to form radon and momentum is conserved. They give you the velocity of the alpha particle and you know that the momentum is conserved so you just have to set (4g/mol) (1.5x10^7)=(226g/mol)(velocity of radium). Solve for the velocity of radium. Think of an explosion when an object breaks off in to a big and a small piece. Because momentum is always conserved (in an ideal situation) the mass x velocity of the big piece has to equal the mass x velocity of the small piece.

41) Again, don't get hung up on equations. Understand what's actually going on and then try solving the problem. Basically, the question is telling you that an object is 4 focal lengths away from a convex (converging) lens. This should immediately tell you that because the distance > focal length, the image that the object forms is going to be real, smaller than the original object, and inverted. Because the question is asking you for a magnification ratio, you can get rid of all the ratios that say that the image is going to be larger than the object (C and D). Now you can you the magnification equation in which Magnification= -distance of image/distance of object=height of image/height of object. Now just plug and chug..(4/3f)/4f = 1/3=height of image/height of object..So the answer is A.

 

[dmplz707]

Hey guys for #35, I guess I got a bit confused because I tried solving this problem using intermolecular forces. I figured since Oxalic Acid has 2 -COOH groups, that allows for more H-bonding and thus a higher melting point = higher freezing point and so I thought Crotonic Acid would thus have the lower freezing point. Could someone clarify why my reasoning didn't work in this case? Thanks.

 

[MT Headed]

Freezing (melting) point depression of a solvent only depends on particle concentration. Oxalic acid breaks up into 3 particles, crotonic only breaks up into 2 particles. It's just a knee-jerk reaction. Melting point depression and boiling point elevation are both colligative properties, depending on molality, i.e. moles of particles / kilogram of soln.

Your approach didn't work because the effects you describe are so much smaller than the effect of the colligative properties.

 

[Hexon]

24) For questions like these you really don't need to know what the frequency of the 2nd harmonic is. All you need to know is that the second harmonic will always have a greater frequency than the first harmonic. Because f=1/T, something with a greater frequency will have a smaller period. Knowing this, (and also knowing that the period of the first harmonic is 1/100=0.01 seconds) you know that your answer has to be less than 0.01 seconds. Thus, the only answer choice that remains is A.

38) You can take the clue from the question when it says to assume that the momentum of the gamma particle is negligible to the alpha particle. This means that when the decomposition reaction happens and the alpha particle (m=4g/mol) breaks off of Radium (m=226g/mol) in order to form radon and momentum is conserved. They give you the velocity of the alpha particle and you know that the momentum is conserved so you just have to set (4g/mol) (1.5x10^7)=(226g/mol)(velocity of radium). Solve for the velocity of radium. Think of an explosion when an object breaks off in to a big and a small piece. Because momentum is always conserved (in an ideal situation) the mass x velocity of the big piece has to equal the mass x velocity of the small piece.

41) Again, don't get hung up on equations. Understand what's actually going on and then try solving the problem. Basically, the question is telling you that an object is 4 focal lengths away from a convex (converging) lens. This should immediately tell you that because the distance > focal length, the image that the object forms is going to be real, smaller than the original object, and inverted. Because the question is asking you for a magnification ratio, you can get rid of all the ratios that say that the image is going to be larger than the object (C and D). Now you can you the magnification equation in which Magnification= -distance of image/distance of object=height of image/height of object. Now just plug and chug..(4/3f)/4f = 1/3=height of image/height of object..So the answer is A.

thank you so much for your help🙂👍

 

[Joker88]

can someone explained Question 99 to me please? What exactly is the 64 cell stage?

I cant seem to post the diagrams they have on the test but the question is this:

Which of the diagrams below best represents the nucleus of an embryo at the 64 cell stage grown from this cell?

 

[Joker88]

also

#119. Based on the passage, the mutation in the dna in affected males from Family 2 most likely results in:

A. the replacement of a single amino acid in Protein R
B. the replacement of a single amino acid in Protein P

Protein R is what phosphorylates Protein P so would Protein R have the replacement amino acid? The problem in family 2 is that the Protein P was not phosphorylated... (answer is A)

#139. When a drop of BR2 in CCl4 is added to Product B, the resulting solution will be:

B: colorless, because product B contains a carbon-carbon double bond.

Product A was dehydrated orginally is that what created the C=C bond? If thats the case, i couldnt recall the reaction at the time...

 

[MT Headed]

#119. Based on the passage, the mutation in the dna in affected males from Family 2 most likely results in:

A. the replacement of a single amino acid in Protein R
B. the replacement of a single amino acid in Protein P

We know that
I) protein R is normal sized in males and females of family 2 (rule 3)
II) protein R functions just fine in females of family 2, phosphorylating protein P (rule 4)
III) a perfectly good female protein R is incapable of phosphorylating the protein P of males in family 2 (rule 5)

therefore, the defect in the males of family 2 is most likely in male protein P

 

[MT Headed]

#139. When a drop of BR2 in CCl4 is added to Product B, the resulting solution will be:

B: colorless, because product B contains a carbon-carbon double bond.

Product B was created by a dehydration of product A with hot concentrated acid. Product A had an alcohol group. When it was dehydrated, the OH ran off with an H+ to create water (an excellent leaving group) and a C=C double bond was left behind like a scar.

Rule 5 says that Br2 will go from red to colorless in the presence of a double bond.

 

[MT Headed]

can someone explained Question 99 to me please? What exactly is the 64 cell stage?

It represents the organism after it divided 8 times to create 2^8 identical cells. But the more important question is who cares? Even if they took the snapshot at the 100 trillion cell stage of an adult human, all of the chromosomes would look exactly the same as those the 2 cell stage or even the 1 cell stage.

Mitosis creates exact duplicates.

 

[TheMightyBoosh]

i only have the CBT version and perhaps you can post the graph and the question?

for 130 of the BS, passage 5
"in experiment 2, the increased blood pressure resulting from the higher than normal conc. of ADH most likely affected urinary output of substance A by increasing the:

i have an inkling that glomerular filtration rate is just "the better answer," but perhaps there's a better explanation why C (water reabsorption from the tubules) isn't as good. i understand the whole increase in blood pressure = in crease in GFR, but incr in ADH is also incr water reabsorption.

then in the answer as they explained to rule out C, they say "increasing blood pressure should increase flow of fluid through the kidney and decrease water reabsorption, so the answer choice is incorrect. if the increased blood pressure is due to ADH, then water would be reabsorbed?

I'm confused with this as well, anyone have an explanation?

 

[km1865]

BS section:

vacuum filtration passage in the BS section. So the question read, which of the following experimental modifications would most improve the degree of separation between limonene an (+)-Carvone?

The correct answer is slow the heating rate, that makes sense to me since slowing the heating rate would cause slower boiling and more evaporation/condensation cycles on the glass beads in the fractional column, right? But, what I dont understand is why increasing the pressure would make the boiling points between the two differ even more (i.e. if the boiling points are being raised due to increasing pressure in the column, then the boiling point of each compound is becoming even more different from the other one making the separation better), whereas decreasing the pressure would have the opposite effect (decrease BP, and make the BP range b/w the two compounds even more narrow making it a bad separation).

sorry if someone already asked this, just didnt have the time to look for it lol. Thanks!

 

[Blaughable]

i only have the CBT version and perhaps you can post the graph and the question?

for 130 of the BS, passage 5
"in experiment 2, the increased blood pressure resulting from the higher than normal conc. of ADH most likely affected urinary output of substance A by increasing the:

i have an inkling that glomerular filtration rate is just "the better answer," but perhaps there's a better explanation why C (water reabsorption from the tubules) isn't as good. i understand the whole increase in blood pressure = in crease in GFR, but incr in ADH is also incr water reabsorption.

then in the answer as they explained to rule out C, they say "increasing blood pressure should increase flow of fluid through the kidney and decrease water reabsorption, so the answer choice is incorrect. if the increased blood pressure is due to ADH, then water would be reabsorbed?

The main thing in this question is correctly reading and answering the question stem. It is not asking how does the higher than normal ADH level affect urinary output, it is saying how does the high blood pressure caused by the higher than normal ADH levels affect urine output.

High ADH -> Increased water reabsorption -> High blood pressure -> Increased glomerular filtration rate

 

[TheMightyBoosh]

The main thing in this question is correctly reading and answering the question stem. It is not asking how does the higher than normal ADH level affect urinary output, it is saying how does the high blood pressure caused by the higher than normal ADH levels affect urine output.

High ADH -> Increased water reabsorption -> High blood pressure -> Increased glomerular filtration rate

Just saw this, thanks for the response 🙂

 

[notbobtrustme]

I have a question about question #163 in the Biological Sciences section.

The question states : Glucose is labeled with C14 and traced as it's metabolized to CO2, H2O and ATP. When will the label first be detectable in heptacytes.

The correct answer is : D.) First in the cytoplasm then in the mitochondria.

I picked A because PDH complex is in the mitochondria, which oxidizes pyruvate to acetyl-CoA and CO2. In the cytoplasm, glucose is oxidized to pyruvate, which is then reduced to lactic acid using NADH, regenerating NAD+. There is no release of CO2 in the cytoplasm.

Unless I'm missing from the question stem, I don't see how you would be able to detect the label in the cytoplasm.

This is my difference between a 14 and a 15 🙁

 

[MT Headed]

The question states : Glucose is labeled with C14 and traced as it's metabolized to CO2, H2O and ATP. When will the label first be detectable in heptacytes.

The correct answer is : D.) First in the cytoplasm then in the mitochondria.

Yeah I think I got that one wrong too. The point they are trying to make is they want you to trace the movement of the carbons from glucose to (eventually) CO2. You answered it assuming they wanted to trace the carbons after they became CO2.

I wouldn't sweat the 14 vs. 15, any score 12+ is essentially a perfect score if you read between the lines on the AAMC acceptance table.

 

[paul411]

I have a question about question #163 in the Biological Sciences section.

The question states : Glucose is labeled with C14 and traced as it's metabolized to CO2, H2O and ATP. When will the label first be detectable in heptacytes.

The correct answer is : D.) First in the cytoplasm then in the mitochondria.

I picked A because PDH complex is in the mitochondria, which oxidizes pyruvate to acetyl-CoA and CO2. In the cytoplasm, glucose is oxidized to pyruvate, which is then reduced to lactic acid using NADH, regenerating NAD+. There is no release of CO2 in the cytoplasm.

Unless I'm missing from the question stem, I don't see how you would be able to detect the label in the cytoplasm.

This is my difference between a 14 and a 15 🙁

Step 1: The labeled glucose enters the cell and glycolysis (glucose -> pyruvate) takes place in the cytoplasm. So you first will detect the label in the cytoplasm

Step 2: The pyruvate enters the mitochondria for Krebs Cycle (which produces more ATP and CO2). So you will detect the label in the mitochondria now.

Here's a diagram which might be helpful (sorry I couldn't find a better one):

 

[notbobtrustme]

Yeah I think I got that one wrong too. The point they are trying to make is they want you to trace the movement of the carbons from glucose to (eventually) CO2. You answered it assuming they wanted to trace the carbons after they became CO2.

I wouldn't sweat the 14 vs. 15, any score 12+ is essentially a perfect score if you read between the lines on the AAMC acceptance table.

yea, this is true, but at the same, people say that this test is extremely easy. I was a bit surprised since I was scoring 9-10s on the EK tests in the back of the book.

Thanks Paul and MT Headed, I figured I mis-understood the question stem. When I read it, I got the impression the read-out was CO2 released.

 

[vuze142]

4) A soluble form of Pb2+ can be carefully added to a solution to sequentially precipitate and separate anions present in the solution. When Pb2+ is added, in what order will the following anions be precipitated?

-In the passage, it shows that precipitation occurs in the order of PbSO4, PbI2, and PbCO3. The answer is Co32- and then I-. I really can't figure this question out. If PbSO4 precipitates first, then isn't it the least soluble?

 

[sjrosen9]

.

 

[moto_za]

.

...

 

[yoyohomieg5432]

Hi, There are a few components of the first passage in the physical sciences section I could use help with.
1) In question 1, I know that the reactants are HCl and PbCO3. i eliminated 2 of them because the reactants were wrong and C because the equation wasn't balanced. I'm trying to figure out how to derive the equation in answer A. I know that since HCl is a strong acid it will dissociate to H+ and Cl-. On the other hand I have no idea what to do with PbCO3. How am I suposed to know that PbCO3 will break down into Pb2+ and CO3 2-? (Does Pb not form a covalent bond with CO3?) (How do I determine the charge on Pb? I imagined the lewis structure for CO3 and reasoned it was -2 so Pb must be +2. is there a better way?) does Pb always have a +2 charge?

2) question 2 talks about the identity of compound A (described in reaction 1). Again, how am i supposed to know that Pb(NO3)2 will breakdown into Pb 2+ + 2NO3-? Does Pb not covalently bond? Why would it just dissociate. Also given is Na2SO4. In this case Na+ is an ionic bond right? (Does Na ever covalently bond?) I deduced that it decomposed to 2Na(+) + SO4(2-). From that I just combined the + charge Pb from the first molecule with the - charge of the other molecule. to get PbSO4. This seems kind of shallow way to do it, is there a more accurate approach?

 

[marcherie]

why arent carbons 2 and 7 stereocenters? is it because of the double bonds?

Please see attachment!

 

[TX500]

why arent carbons 2 and 7 stereocenters? is it because of the double bonds?

Please see attachment!

Yes. You need four unique groups.

 

[BryanNextStep]

1)How am I suposed to know that PbCO3 will break down into Pb2+ and CO3 2-? does Pb always have a +2 charge?

2) how am i supposed to know that Pb(NO3)2 will breakdown into Pb 2+ + 2NO3-?

1. The test is going to expect you to be familiar with common complex ions. They'll expect you to know off the top of your head the structure and charges, for example, of carbonate, sulfate, sulfite, nitrate, nitrite, perchlorate, chlorate, chlorite, hypochlorite, and others.

There are a couple of ways to deal with this - the most common, of course, is to pick up a set of review books from a prep company and just memorize whatever ions they have listed in their gen chem chapter on solution chemistry.

You could also go back to your old textbook (if you still have it) from Chem 101 and find a list there of common complex ions.

Finally, you could just work your way through all the AAMC tests and the practice tests from some other company (I typically recommend the 10 gold standard tests to my tutoring students) and every time you come to a complex ion you don't know, make a flashcard for it.

Lead, like most metals, has several different possible oxidation states, although the +2 is by far the most common and probably the only one you'll encounter on the MCAT

2. Again, you'll be expected to know the nitrate ion walking into the test.

Good luck! 🙂

 

[marcherie]

Yes. You need four unique groups.

Yes but doesnt the double bond make it an alkene, and alkenes with*two different substituents*at each end of the C=C can exist as stereocenters. Carbon 2 has two diff substituents 😕

 

[stephster416]

BS section:

vacuum filtration passage in the BS section. So the question read, which of the following experimental modifications would most improve the degree of separation between limonene an (+)-Carvone?

The correct answer is slow the heating rate, that makes sense to me since slowing the heating rate would cause slower boiling and more evaporation/condensation cycles on the glass beads in the fractional column, right? But, what I dont understand is why increasing the pressure would make the boiling points between the two differ even more (i.e. if the boiling points are being raised due to increasing pressure in the column, then the boiling point of each compound is becoming even more different from the other one making the separation better), whereas decreasing the pressure would have the opposite effect (decrease BP, and make the BP range b/w the two compounds even more narrow making it a bad separation).

sorry if someone already asked this, just didnt have the time to look for it lol. Thanks!

Bump. Anyone know the answer to this? I also didn't understand the part in the answer key's explanation that stated lowering pressure would not only lower the BP of each liquid, but narrow the difference between their BPs. Thanks!

 

[sp808]

For PS, Q#27 how is the period of the waveform in 1c equal to the period of the first harmonic (solid line)? The period is visibly and significantly shorter, no?

 

[yoyohomieg5432]

1. The test is going to expect you to be familiar with common complex ions. They'll expect you to know off the top of your head the structure and charges, for example, of carbonate, sulfate, sulfite, nitrate, nitrite, perchlorate, chlorate, chlorite, hypochlorite, and others.

There are a couple of ways to deal with this - the most common, of course, is to pick up a set of review books from a prep company and just memorize whatever ions they have listed in their gen chem chapter on solution chemistry.

You could also go back to your old textbook (if you still have it) from Chem 101 and find a list there of common complex ions.

Finally, you could just work your way through all the AAMC tests and the practice tests from some other company (I typically recommend the 10 gold standard tests to my tutoring students) and every time you come to a complex ion you don't know, make a flashcard for it.

Lead, like most metals, has several different possible oxidation states, although the +2 is by far the most common and probably the only one you'll encounter on the MCAT

2. Again, you'll be expected to know the nitrate ion walking into the test.

Good luck! 🙂

I guess my question was more along the lines of this: is PbCO3 not a covalent bond? (i.e. Pb isn't covalent bonded to C?) If not, do you know that this is an ionic interaction simply because CO3- is a complex ion?

It seems like I could counter argue that like this: in H2O, both hydrogens are covalently bonded to oxygen, but OH- is a complex ion. So by the logic I stated above I would reason that H-OH is an ionic interaction when it really isn't.

Also: I'm confused with question 4 of the same passage (passage 1 of physical sciences). I understand that So4 precipitates, then I, then CO3. In there explanation they then say that this shows that PbCo3 is less soluble than PbI2 which is less soluble than PbSO4. How did they figure that out?

 

[yoyohomieg5432]

For PS, Q#27 how is the period of the waveform in 1c equal to the period of the first harmonic (solid line)? The period is visibly and significantly shorter, no?

trace the zero crossings from the first harmonic down to 1c, they are at the same locations, so the period must be the same

 

[AFLATPEG]

why arent carbons 2 and 7 stereocenters? is it because of the double bonds?

Please see attachment!

you need atleast 4 different "things" attached to that carbon in order for it to be sterocenters. those carbons have only 3 things bonded to them bcus of the double bonds, yes.

 

[AFLATPEG]

I have a question about question #163 in the Biological Sciences section.

The question states : Glucose is labeled with C14 and traced as it's metabolized to CO2, H2O and ATP. When will the label first be detectable in heptacytes.

The correct answer is : D.) First in the cytoplasm then in the mitochondria.

I picked A because PDH complex is in the mitochondria, which oxidizes pyruvate to acetyl-CoA and CO2. In the cytoplasm, glucose is oxidized to pyruvate, which is then reduced to lactic acid using NADH, regenerating NAD+. There is no release of CO2 in the cytoplasm.

Unless I'm missing from the question stem, I don't see how you would be able to detect the label in the cytoplasm.

This is my difference between a 14 and a 15 🙁

yeah, it basically asks you to TRACE the 14C throughout its process. i chose mito initially, but then re-read the question. it can be traced from glycolysis (cytoplasm) all the way to ETC.

 

[AFLATPEG]

Hi!

For #35, it asks us to find the solution with the lowest freezing point. Crotionic has a MP of 71.6 and Oxalic has 101. I think from AAMC#10 it said that freezing point is the same thing as the melting point (which kinda made sense to me intuitively), so I chose Crotionic. The answer was Oxalic acid.

Why does oxalic acid have the lower freezing point when its melting point is higher?

this is basically asking you if you know your colligative properties. it says they are in (aq) solution, meaning they're in water & they've probably dissociated. you know T=kim and i is the number of ions it dissociates to. the greater the number of ions it dissociates to, the greater the temperature depression. Oxalic acid has 2 -OH groups and Crotionic has only 1.

 

[Hirwipi]

Can someone please explain #47 in layman's terms? The MCAT AAMC explanation is a bit too heavy for me... Also -- is there a good website/forum/book for content review on this? My Kaplan "Gen Chem Review Notes" book isn't too helpful...

Here is the question:
Which of the following species has the smallest concentration in 98% H2SO4?
a. SO4 [2-] -- correct answer
b. H2SO4
c. H30 [+]
d. HSO4 [-]

Thank you!

 

[Hirwipi]

Can someone please explain #47 in layman's terms? The MCAT AAMC explanation is a bit too heavy for me... Also -- is there a good website/forum/book for content review on this? My Kaplan "Gen Chem Review Notes" book isn't too helpful...

Here is the question:
Which of the following species has the smallest concentration in 98% H2SO4?
a. SO4 [2-] -- correct answer
b. H2SO4
c. H30 [+]
d. HSO4 [-]

Thank you!

NVM, I actually figured it out (a basic oxidation number question hidden in a bunch of extra words!)

 

[AFLATPEG]

Regarding AAMC 3, Question 27: The period of the waveform shown in Figure 1c is the:

A. same as the period of the first harmonic <-- ANSWER
B. same as the period of the second harmonic

The answer states that the waveform repeats at zero displacement for the first harmonic, but this appears to be true for the 2nd harmonic as well. Why would you choose the 1st over 2nd harmonic?

If you look at Figure 1c, the time it takes to finish 1 cycle (period) is the same time as the first harmonic in Figure 1a.

the 2nd harmonic in Fig 1a's Period is half the time of the 1st harmonic.

 

[ihatebluescrubs]

In PS #15 you have a rectangle 4m wide by 3m long, one force of 4N parallel to the 4m at the corner and another force of 3N pointing parallel to the 3m side. They ask you to find the force on a uknown vector to ensure translational equilibrium.

The answer explanation didn't take into consideration the distance of the 3N and 4N vector from the center (where the unknown vector originates from) Why is that? Don't we have to determine the energy lost by placing the force vectors far on the edge of the rectangle?

 

[Synapsis]

If you look at Figure 1c, the time it takes to finish 1 cycle (period) is the same time as the first harmonic in Figure 1a.

the 2nd harmonic in Fig 1a's Period is half the time of the 1st harmonic.

I actually liked that question. Reminded me that when I get something I'm not completely sure of, I need to check the passage again, including graphs and such.

 

[ifonlyifonly]

For verbal #55, Roman number 2 says "fewer law enforcement officials would be retained" What does "retained" mean? They'd be fired? Or would they be reassigned?

 

[bmoredoc]

For #77 on the R version of the test it asks about how much work is done to lift a 4 kg weight 5 m off the ground by using a pulley system. The pulley system has 2 ropes which support the pulley which holds the weight. Because the weight bearing pulley has 2 ropes, its mechanical advantage is equal to the weight of the mass (i.e. 40 N) divided by 2. This means that the force applied to the non-weight bearing pulley must be 20 N in order to lift the weight. This to me seems to indicate that the work being done is equal to 20 N (5 m) = 100 NM
However, the kaplan solutions provided on chris mcat stuff says that the work done is actually 40 N (5 m) = 200 NM. Am I missing something here or did kaplan fug up?

 

[FeinMS]

For number 30, it asks..
2 identical voltage sources are connected in parallel. Compared to voltage generated by a single source, how will the new voltage differ?
The answer is that the voltage is the same.
How does batteries in parallel have the same voltage as one? Is there a formula for equivalence voltage in parallel?

 

[Temperature101]

For #77 on the R version of the test it asks about how much work is done to lift a 4 kg weight 5 m off the ground by using a pulley system. The pulley system has 2 ropes which support the pulley which holds the weight. Because the weight bearing pulley has 2 ropes, its mechanical advantage is equal to the weight of the mass (i.e. 40 N) divided by 2. This means that the force applied to the non-weight bearing pulley must be 20 N in order to lift the weight. This to me seems to indicate that the work being done is equal to 20 N (5 m) = 100 NM
However, the kaplan solutions provided on chris mcat stuff says that the work done is actually 40 N (5 m) = 200 NM. Am I missing something here or did kaplan fug up?

Work done is just the energy spent to lift the object... E = mgh...= 4x10x5 = 200 J

 

[monkeyvokes]

For #77 on the R version of the test it asks about how much work is done to lift a 4 kg weight 5 m off the ground by using a pulley system. The pulley system has 2 ropes which support the pulley which holds the weight. Because the weight bearing pulley has 2 ropes, its mechanical advantage is equal to the weight of the mass (i.e. 40 N) divided by 2. This means that the force applied to the non-weight bearing pulley must be 20 N in order to lift the weight. This to me seems to indicate that the work being done is equal to 20 N (5 m) = 100 NM
However, the kaplan solutions provided on chris mcat stuff says that the work done is actually 40 N (5 m) = 200 NM. Am I missing something here or did kaplan fug up?

Kaplan's correct. If you are using a pulley system with two ropes then you will lift the weight half as fast if you lifted it directly up. Simple machines don't change the amount of work done, but they can change the force.
Think about it, both ropes are applying 20 newtons to lift the 40 newton weight. When you apply this force for a given time you will only lift the weight half as high if you were applying all 40 newtons from a single rope (this one isn't easy for me to explain clearly so i apologize).

check out the simple machines section on the hyperphysics website or try viewing some gifs of pulleys to see what I mean