Group Study Thread and Other Micellaneous Posts

[SDN]

This thread is for students to ask and answer each other's questions for the MCAT, DAT, OAT, and PCAT subjects. All posts from the other Q & A threads that are not either students' questions or moderators' replies will be moved to this thread. Students, please post your own answers to other students' questions here in this thread--or else in the main MCAT forum--rather than in the regular Q & A threads.

If you are a pre-health (MCAT, PCAT, DAT, OAT) test prep instructor, or you have a graduate-level background in one of the MCAT subjects, or you are a senior undergrad who scored well on the MCAT, and you would like to help answer questions for one of the regular Q & A threads, please PM Shrike or QofQuimica and let them know. Again, all undergrad students who are currently studying for any of these tests should NOT post answers to other students' questions in any of the regular Q & A threads. Thanks to everyone for your cooperation..

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[liverotcod]

Cool. I'll bet Shrike also proposed credential requirements for anyone answering questions.

 

[Nutmeg]

Cool. I'll bet Shrike also proposed credential requirements for anyone answering questions.

I finally realized what your moniker is.

 

[sunnyjohn]

Yeah! Let the learning begin!

 

[Shrike]

Cool. I'll bet Shrike also proposed credential requirements for anyone answering questions.

I did.

But... I am happy to have help from anyone whose answers are (1) correct; (2) clear; and (3) constructed to help people do better on MCAT problems. Clarity and consiseness may occasionally be necessary victims of the inherent complexity of the subject matter, but appropriatness for the MCAT, never.

I will be moderating the physics thread, or perhaps co-moderating physical sciences with Q -- this is still be discussed. Anyone wishing to post one, or one hundred, answers to physics questions, please PM me.

 

[Shrike]

Two excellent users, Shrike and QofQuimica, have proposed setting up a Q&A subforum within the MCAT forum. They will make themselves available to answer questions for those studying for the MCAT.

This forum will operate differently than the standard forum. Only posts asking specific questions or providing direct answers will be allowed. Other discussions about the MCAT will be moved to the main MCAT forum.

Thank you, Lee (and everyone else who helped), for giving us this opportunity. Now we've just got to prove it was worth the trouble.

 

[liverotcod]

I am happy to have help from anyone whose answers are (1) correct; (2) clear; (3) concise; and (4) constructed to help people do better on MCAT problems. Celerity and conciseness may occasionally be necessary victims of the inherent complexity of the subject matter, but appropriatness for the MCAT, never.

Oh, I agree! But you must admit to being, from time to time, rather shrill on this point.

As for myself, even though I fared reasonably well on the MCAT, I would not consider myself an expert on any topic. I found it to be much less a test of knowledge and more an exercise in reading comprehension and application of basic principles.

 

[QofQuimica]

Cool. I'll bet Shrike also proposed credential requirements for anyone answering questions.

I think we've agreed that this should not be a requirement, or if it is, it should be loosened from what was originally suggested.

 

[Shrike]

Oh, I agree! But you must admit to being, from time to time, rather shrill on this point.

I do so admit, though I might have chosen a different (albeit no less friendly) adjective.

Your help will be welcome. Everyone's help will be welcome, if it meets the requirements (which are really just common sense).

 

[Shrike]

I think we've agreed that this should not be a requirement, or if it is, it should be loosened from what was originally suggested.

As I've shown in the stickified thread, I believe we should pass the mantle for granting imprimaturs to the individual thread moderators. In turn, those mods will realize, as I and I'm sure you already do, that the more help we accept, the more reasonable our task will be.

 

[liverotcod]

I think that there will be a lot of repeat questions, so hopefully they won't get too long because a lot of people will find that their questions have already been answered. What do you (or anyone else) think?

Unfortunately, I think you may be overestimating many SDNers' willingness to look for answers themselves by reading over existing threads. One thought would be to create a solutions library of various problem types--didn't you suggest a FAQ in a previous message?--and then link the stock answer in for incoming questions.

 

[Shrike]

Thank you for setting up our sub-forum, Lee. Shrike, I had another thought. Since we have a single sub-forum, maybe what we could do would be to organize threads by subtopics? That way, if someone is looking for help with optics, say, there would be a single optics thread for them to read through. But a magnetism question or a density question would each go to its own thread, not mixed in with the optics. The individual threads might get long and cumbersome eventually, but I think that there will be a lot of repeat questions, so hopefully they won't get too long because a lot of people will find that their questions have already been answered. What do you (or anyone else) think?

I think this is a goal at which we can aim, but we won't be hitting it for a while. Why don't we keep each subject together for now, and consider splitting the threads later?

I do think a FAQ list at the top of each thread will eventually be the most valuable contribution we make.

Now that we have our own forum (thank you again!), do you want to co-moderate Physical Sciences with me, or have your own Chemistry thread(s)?

 

[liverotcod]

I do so admit, though I might have chosen a different (albeit no less friendly) adjective.

Ah, but shrill was just irresistable, given your alter-ego. Listen!

 

[Shrike]

Ah, but shrill was just irresistable, given your alter-ego. Listen!

Wow, you're good -- most people don't even know what a shrike is.

The call is rather dull, but the song is interesting. And that of the Northen Shrike, a species about which you won't find much information (and of which I couldn't fnd a decent avatar picture) is better.

I'd have PMed you about this, but that capability seems to have gotten disabled when I got moderating privileges. I'll take that trade.

 

[mshheaddoc]

Glad to see this finally came to be. I'm sure I will be using this for next April! Good luck with the forum Shrike and Q

 

[QofQuimica]

Unfortunately, I think you may be overestimating many SDNers' willingness to look for answers themselves by reading over existing threads. One thought would be to create a solutions library of various problem types--didn't you suggest a FAQ in a previous message?--and then link the stock answer in for incoming questions.

Ok, that makes sense. We'll answer questions and have a FAQ thread for each subject, and then when the questions come up again, we can link people to the answer post in the FAQ thread.

Shrike, I am willing to go either way, whichever your physicness prefers. I guess if we go with individual FAQ threads, we should decide how we will handle questions that are interdisciplinary. Or, alternatively, we could split the difference, and do both: ex. have a gen chem FAQ, a physics FAQ, and a physical science FAQ. Ditto for BS, and then separate ones for VR, WS, and strategy? If we go this way, it's a lot of threads (9 total: 3 for BS, 3 for PS, 1 for VR, 1 for WS, and 1 for strategy), but then we could assign moderating duties to each FAQ thread. (ex. you could do physics, I could do gen chem, and we could both do physical sciences.) What do you think?

 

[Shrike]

Shrike, I am willing to go either way, whichever your physicness prefers. I guess if we go with individual FAQ threads, we should decide how we will handle questions that are interdisciplinary. Or, alternatively, we could split the difference, and do both: ex. have a gen chem FAQ, a physics FAQ, and a physical science FAQ. Ditto for BS, and then separate ones for VR, WS, and strategy? If we go this way, it's a lot of threads (9 total: 3 for BS, 3 for PS, 1 for VR, 1 for WS, and 1 for strategy), but then we could assign moderating duties to each FAQ thread. (ex. you could do physics, I could do gen chem, and we could both do physical sciences.) What do you think?

I propose we use the six-thread model (do we need a separate thread for WS?), and we'll deal with interdisciplinary issues when and if they arise. I think that people will have an easier time finding information if we track, roughly, the subject divisions they see in the reference material (and courses) that most of them are using. Boring, but effective.

So if you agree, I'll just take physics for now; chemistry's yours. Not that I don't like the idea of co-moderating with you, you understand.

 

[jeepgirl]

Hey y'all,
I just wanted to say thanks for this! It's a great idea . I know I'll be back once my MCAT prep gets kicked into serious gear.

Again, much thanks .

 

[QofQuimica]

I propose we use the six-thread model (do we need a separate thread for WS?), and we'll deal with interdisciplinary issues when and if they arise. I think that people will have an easier time finding information if we track, roughly, the subject divisions they see in the reference material (and courses) that most of them are using. Boring, but effective.

So if you agree, I'll just take physics for now; chemistry's yours. Not that I don't like the idea of co-moderating with you, you understand.

I don't know if we need a WS one or not. I guess people don't ask many questions about WS, but if there were a thread, maybe they would? Ok, so let's go with your six (physics, gen chem, organic, bio, VR/WS and strategy/general) for now.

I DO think that you don't want to moderate with me. But I guess I'll survive.

Ok, everyone, feel free to ask away.

 

[Shrike]

I DO think that you don't want to moderate with me. But I guess I'll survive.

Hey, baby, wanna moderate together?

(See, I don't think it quite captures the mood.)

 

[SDN]

Wow, you're good -- most people don't even know what a shrike is.

The call is rather dull, but the song is interesting. And that of the Northen Shrike, a species about which you won't find much information (and of which I couldn't fnd a decent avatar picture) is better.

I'd have PMed you about this, but that capability seems to have gotten disabled when I got moderating privileges. I'll take that trade.

Fixed the PM problem!

 

[Shrike]

Fixed the PM problem!

Thank you.

 

[QofQuimica]

Hey, baby, wanna moderate together?

(See, I don't think it quite captures the mood.)

Hey, you stick to physics! *I* get to make the chemistry.

 

[QofQuimica]

This thread is for students to ask and answer each other's questions for the MCAT, DAT, OAT, and PCAT subjects. All posts from the other Q & A threads that are not either students' questions or moderators' replies will be moved to this thread. Students, please post your own answers to other students' questions here in this thread--or else in the main MCAT forum--rather than in the regular Q & A threads.

If you are a pre-health (MCAT, PCAT, DAT, OAT) test prep instructor, or you have a graduate-level background in one of the MCAT subjects, or you are a senior undergrad who scored well on the MCAT, and you would like to help answer questions for one of the regular Q & A threads, please PM Shrike or me and let us know. Again, all undergrad students who are currently studying for any of these tests should NOT post answers to other students' questions in any of the regular Q & A threads. Thanks to everyone for your cooperation..

 

[liverotcod]

In other words, I would like a sticky for current useful links to important threads. This might eliminate many of the over excessive threads which ask the same question every other day.

Ummmm... you mean like this stickied thread?

(sorry! )

 

[EvoDevo]

Thanks!!!! Didn't realize it was updated. I know there used to be one last summer, but it didn't have much links.

I guess EvoDevo updated it. Now if only people would look at it before posting 5 threads a day on the very same topic.

You're asking way too much of people. Most can't be bothered to actually look info up before blathering on.

 

[bananaface]

One more thing I would like to propose:

Not for MCAT, but for Preallo.......

I would recommend bringing up PA related propositions in PA, so as not to take away from the discussion here. Q&S need to hammer out the Q&A.

 

[Shrike]

Hey, you stick to physics! *I* get to make the chemistry.

Just catalyzin', darling. Activation energy and all. Doesn't change the end result, of course.

 

[Shrike]

Q&S need to hammer out the Q&A.

... and then get to QC.

Thanks for your help, bananaface.

 

[Kussemek]

Thanks for this forum, for those that might be retaking the exam and who have done the reading that a TPR or Kaplan course might require...how do you think one should approach studying this time around?

 

[Shrike]

Thanks for this forum, for those that might be retaking the exam and who have done the reading that a TPR or Kaplan course might require...how do you think one should approach studying this time around?

Go ahead and put this question in the "general questions" thread, when it appears. Perfect grist for the mill.

 

[sglacal]

How do i get density of a certain gas using PV=nRT ?

PV = nRT --> n / V = P / RT
D = m/V = n*MM / V = P*MM / RT
(MM: molar mass of the gas)

 

[Shrike]

Yes.

 

[deuist]

With all of this talent on the MCAT floating around here, I wonder why the various posters don't get together and create an SDN Guide to the MCAT.

 

[Shrike]

With all of this talent on the MCAT floating around here, I wonder why the various posters don't get together and create an SDN Guide to the MCAT.

I think that's kind of what we're doing now.

QofQuimica: lol, we've discussed doing it. But actually, a forum is better; this will be a kind of a living, evolving SDN Guide to the MCAT.

 

[gotgame83]

Just wanted to thank everyone that is contributing to this forum. The explanations that are being provided are amazing. Without a doubt this will be a great asset to all those taking the mcat.

 

[goldfish85]

This mnemonic comes to us courtesy of Turkeyman.

So you have uncle Ben(Benzene), and he's a lazy leech.
If you lend him money to go party(electron donating), he'll love you, and want you sit across or next to him at the dinner table (ortho/para).
If you don't lend him any money, he'll hate you and want at least 1 person between you and him (meta).

One exception is that Uncle Ben respected Uncle Hal (halides) even if he didnt give Ben any electrons, because of his character. So, in effect, he would always let Uncle Hal sit across or next to him at the dinner table.

Actually, this mnemonic is from EK's Audio Osmosis

 

[Dave_D]

Several people have pointed out common spelling and grammar mistakes. It's always a good idea to try and correct these in your writing. However, it's important to know that the MCAT Writing Sample IS NOT a spelling or grammar test. Your score is based on how well you fulfill the three tasks and write a unified essay.

I don't know if I'd agree with that. Maybe in general it's true but I still think in my case it's not. I took the MCAT in April 05 and got an M. As far as I'm concerned I completed the 3 tasks (As per Kaplan) and also had unity.(So I was expecting at least an O. Hell, I still remember the prompt for at least one and my take on it for anybody that cares. Then again I might be breaking copyright law by revealing the prompt even if a paraphrase it.) Actually I would describe my essays as blatantly doing the tasks. The only thing that I can think of would be maybe it was my handwriting, which is so bad people kept telling me I wrote like a doctor when I was a kid. If that's why I got the grade I did I'd understand, otherwise my score is yet another WS anomaly.

 

[blankguy]

Aaaarrrrggggghhhhhh! Sorry I just felt like doing that. It really is frustrating trying to get the sense of what the author is saying in the passages. I have resorted to writing key ideas for each paragraph and I got a 4
I am trying to get a sense of the author's tone. I felt like I was making progress in the EK material but it is so...frustrating.

 

[Neurolemma]

That said, here's what I personally did. I would read the passage through, reading critically but not taking a huge amount of time to figure out details I didn't understand. I did make sure that I understood the overall argument and thrust of the passage though. Then I read the questions, answered the ones I knew, and referred back to the passage for the few that I didn't.

I never skipped passages, because for me it was more trouble than it was worth to remember what I had to come back to.

Again, my strategy was what personally worked for me. I'm a fast reader (I did always finish ahead of time), I'm good at grasping arguments, and I had a double engineering/humanities major so I was somewhat used to reading humanities passages. (The art ones were the worst for me.) And I'm not used to marking up textbooks so it never really occurred to me to mark up the passages, though I did occasionally underline or star things that I knew I was coming back to.

In general, I think it's a good idea to read the passage first, because if you can get a handle on the argument (as I described upthread) you will be able to answer several of the questions very quickly, and know where things are when you need to refer back. Whether to underline or make notes is up to you - I essentially mapped the passage in my head, but I think most people do better with some actual marks on the page.

Skipping passages, again, is a personal thing, but I'd recommend only doing it if you come to a passage that's making you freak out for whatever reason. If you're going to be wasting time hyperventilating, go on to the next one, but as long as you can stay calm and tackle the passages one by one I think steaming ahead is probably the best way to go.

This is exactly how I, too, prefer to take the test. I think the retention factor is more beneficial in the long run - in terms of time - than immediatly jumping to the questions, and then scanning the passage for answers. The only downside to such an approach is that the paragraphs tend to be written with a lot of "..." interspersed between the sentences. I don't know why they do that. No med textbook is written like that. Hopefully... I'll.... get...... used.....to...... that...... way...... of....... reading.

 

[Neurolemma]

That just shows where they've removed content while editing the passages to be suitable for the MCAT. They take out stuff that's irrelevant or too difficult, but also they cut down on transitions and repetitions, making it more challenging to read.

I suppose I'm like you in that I grasp the main point of an argument fairly quickly, so I won't easily be thrown off by the condensed format. I think thats also part psychology. You kinda "feel" the author. But the use of .... slows down my reading speed more than anything else. I'm simply not used to reading that way. You know how when you're normally reading, and the ... comes up, you automatically slow down. Thats what it is here. The effect isn't that dramatic; I'm managing around a 12 on the practice tests, with a little bit of time to spare, on a fairly consistent basis. Wouldn't mind bringing it up 2 points, however. Every point counts.

 

[hdu]

Yes, it can and is, and for exactly the reason you state. Before the fat is metabolized in the Citric Acid Cycle, it must be converted to Acetyl CoA. This is done by beta oxidation, which produces FADH2 and NADH while consuming one ATP per pair, which gives another 4 ATP per pair of carbon molecules. The total then is 4 from beta oxidation plus 12 from Krebs cycle for a net of 16 ATP per two carbons, or about 8 ATP per carbon.

Hi!
I am sorry. I did not understand the question or the comments.
I think that a "fair" or more appropriate question would be about comparing the number of ATP produced during the total oxidation of a glucose molecule, and the total oxidation of a 6 carbon fatty acid, not a triglyceride or glycerol.
Oxidation of a 6 carbon fatty acid:
We spend 2 ATP for activation
Fatty acid +ATP+CoA ----------- Acyl CoA + AMP +2P

Number of acetyl CoA produced: 3 (# carbons/2 =6/2 = 3)

#of rounds to convert the fatty acid in Acetyl Co A = 2 (number of acetyl CoA -1)

( Or you can see it better:

C-C-C-C-C-C

1st. round: C-C-C-C + C-C

 

[hdu]

Yes, it can and is, and for exactly the reason you state. Before the fat is metabolized in the Citric Acid Cycle, it must be converted to Acetyl CoA. This is done by beta oxidation, which produces FADH2 and NADH while consuming one ATP per pair, which gives another 4 ATP per pair of carbon molecules. The total then is 4 from beta oxidation plus 12 from Krebs cycle for a net of 16 ATP per two carbons, or about 8 ATP per carbon.

I think that the real comparition would be glucose vs 6 carbon fatty acid:

6 carbon fatty acid yields 3 acetyl Co A in 2 rounds of beta-oxidation

3x12 = 36
Each round 5 ATP (1 NADH +1FADH2) 2x5 =10

Minus 2 ATP used for activation of the fatty acid (1 ATP ---AMP + 2P)

Total 44 ATP > 36 ATP

 

[Nutmeg]

I think that the real comparition would be glucose vs 6 carbon fatty acid:

6 carbon fatty acid yields 3 acetyl Co A in 2 rounds of beta-oxidation

3x12 = 36
Each round 5 ATP (1 NADH +1FADH2) 2x5 =10

Minus 2 ATP used for activation of the fatty acid (1 ATP ---AMP + 2P)

Total 44 ATP > 36 ATP

The question regarded the metabolism of the fatty acid chains of trigyceride.

The beta oxidation mentioned is the part of fatty acid metabolism that provides the additional ATP/carbon that makes fats store more energy.

 

[Lindyhopper]

The beta oxidation mentioned is the part of fatty acid metabolism that provides the additional ATP/carbon that makes fats store more energy.

It often is stated that one sequalae of type I diabetes is ketoacidosis. I'm just speculating, but it would seem like the inability of insulin to get glucuse into the cell results in the hydro. of fatty acids. This in turn results in the release of ketone bodies, which, apparently, results in lowing plasma pH below the optimal range.
If anyone can confirm or correct I'd apprecriate.
Oh, the MCAT level issue. It would seem that this discussion began squarely within the scope of the test. I don't want to break the rules of the thread, but it seems like the natural developement the discussion may now be going beyond that scope. It's your call Nutmeg.

 

[gotgame83]

It often is stated that one sequalae of type I diabetes is ketoacidosis. I'm just speculating, but it would seem like the inability of insulin to get glucuse into the cell results in the hydro. of fatty acids. This in turn results in the release of ketone bodies, which, apparently, results in lowing plasma pH below the optimal range.
If anyone can confirm or correct I'd apprecriate.
Oh.

Im not really sure what you are asking to confirm but yes if insulin is not doing its job either from type 1 or type 2 then beta oxidation occurs. acetyl coa and glycerol go to liver and produces keto bodies primarily for the brain. Ketones are acidic thus lower your pH, this is why some diabetics have something called keto strips. You piss on them and it detects ketones present in your urine.

 

[blankguy]

The B cell mediated involves antibodies specific to an antigen. Once the antigen is bound by the antibody it is eliminated by either having a white cell destroy it by phagocytosis or by a series of reactions with blood proteins destroying it.

The T-cell doesn't involve antibodies instead a T-lymphocyte has antibody like protein on its membrane. It becomes either helper T cells, memory T cells, suppressor T cells and killer T cells. Killer T cells destroy the antigen once it matches with the protein on its membrane. Suppressor T cells wind down the immune response.

To sum it up the B cell method is the "antibody method"
T-cell is the "brute force cell destroys antigen method" Sort of like a cell eating up and destroying its prey.

Secondary response is when the antigen is remembered by the T or B memory cells from previous instrusion. Instead of going through the whole process of "trying to find the antibody from scratch that matches" it already has memory cells that "remember" the antigen hence all they need to do is "crank out from the memory cells specific to that antigen the antibodies or the killer T cellls.

 

[Lindyhopper]

The B-cell doesn't involve antibodies . . .

Wha? I love this thread. I really hope it remains a helpful high quality discussion.

 

[blankguy]

Sorry my mistake. Typo. B cells make atnibodies. T cells don't.
Dam this biology

Typo corrected.

 

[captaintripps]

T cells recognize antigen that has been processed and presented in the context of a major histocompatability complex. CD8 T cells bind Ag/MHC class I and CD4 T cells bind Ag/MHC class II. This interaction activates the T cells to respond by direct cytotoxic action (CD8) or by expression of cytokines to effect the adaptive response (CD4).