Questions from Achiever 1

Shinpe · Jul 30, 2009

So I have a couple of things in the survey of natural sciences I couldn't figure out from Achiever's test 1 solutions:

1. In question 6's solution it says that osteoblasts deposit Ca2+ in response to Calcitonin's presence. I know Calcitonin lowers blood calcium but I thought it does so by reducing osteoclast activity, confirmed by wikipedia. But does anyone have other resources confirming what Achiever is claiming?

2. In quesiton 38, it's asking "The maximum number of chromosome combinations among the gametes of a diploid organism (2n =10) is"

and then in the answer it says since the haploid has 5 chromosomes, it's 2^5. Can some one explain this quesiton? I don't get the question, yet alone the answer lol.

3. In OC question 72, it is asking which compound is not aromatic. There are two possibilities I think. One is the cyclooctene (8-C ring with 4 pi bonds), which is anti-arommatic and I agree. But another option is a three-C ring cation. Where there is a double bond between two of the carbons and the third has a positive charge. Then it says it passes Huckel's rule, so it's arommatic, but isn't the other requirements for aromaticity that it is planar and all carbons have a pair of pi-electrons on them? I don't feel like that is satisfied here. Any thoughts?

4. In 82, it's adding HBr to an alkene in presence of hv and says that it is anti-mark since a free radical would form. I get it that radicals add anti-mark, but don't u need Br2 instead of HBr? I mean wouldnt HBr dissociate completely in water anywayz (well it doesn't say what the solvent is, but anywayz) or wouldn't the bond be too polar for an equal split?

Thanks in advance for answers.

Shinpe · Jul 30, 2009

Any comments???

Sepx · Jul 30, 2009

1. In question 6's solution it says that osteoblasts deposit Ca2+ in response to Calcitonin's presence. I know Calcitonin lowers blood calcium but I thought it does so by reducing osteoclast activity, confirmed by wikipedia. But does anyone have other resources confirming what Achiever is claiming?

I don't have achiever, i don't understand your other questions, except the bio one and a ochem one.
The stimulus is the raising of Ca in the blood, then thyroid hormone secretes calcitonin. NOW, calicitonin lowers the Ca in two ways, one by increasing deposition of Ca on to bones. Ca deposition on to bones ("making bones") is done by osteoblast, therefore increase osteoblast activity.
Another thing calcinotin does is REDUCING Ca uptake in kidney.

If you have campbell, got to endocrine chapter, look for figure about controling blodd calcium: PTH vs Calcitonin. they are antogonistic.

4. In 82, it's adding HBr to an alkene in presence of hv and says that it is anti-mark since a free radical would form. I get it that radicals add anti-mark, but don't u need Br2 instead of HBr? I mean wouldnt HBr dissociate completely in water anywayz (well it doesn't say what the solvent is, but anywayz) or wouldn't the bond be too polar for an equal split?

You need to hit the text book on this one, you getting rxns confused. Study the mechanism for both, they are diffrent.
They are both electrophilic addition rxns though and there is no carobocation rearengement in either one! (but if you additng HBr w/o peroxide, there could be rearengement, always check!)

>addition of HBr w/ peroxide is anti mark addition of Br radical to alkene.

>but addition of Br2 (or Cl2), adds two bromide (chloride) to the alkene.
>also Addition of Br2 with presensence of water results in formation of Halohyrine (alcohol with a halogen).

Sepx · Jul 30, 2009

oops i meant thyroid gland*

Sepx · Jul 30, 2009

also meant halohydrine..sorry about the typos...

Shinpe · Jul 30, 2009

Yeah I just had read somewhere (I think kaplan and forsure wiki) that Calcitonin lowers blood Calcium but LOWERING Osteoclast activity (bone resorption) as opposed to increasing bone deposition by osteoblasts. I guess Campbell does say in the figure "stimulates calcium deposition in bones" which I guess must be done by osteoblasts, but it never mentions it in the text of the chapter, weird.

For that second one, I looked, and I guess you need trace concentrations of HBr, usually delieverd by NBS, to be able to do the radical electrophilic addition, but I guess I should have just taken the hv hint and gone with radical.

Here are the pictures for the other Orgo question. One is cyclooctatetraene, which is anti-aromatic, and the other is the carbocation of cyclopropene. Take the second figure and add a positive charge to the carbon on top.

cyclooctatetraene
http://upload.wikimedia.org/wikipedia/commons/2/2a/Cyclooctatetraene.png

Cyclopropene (add a + charge to the top C)
http://upload.wikimedia.org/wikipedia/commons/e/eb/Cyclopropene-2D-skeletal.png

Shinpe · Jul 30, 2009

And question number 2 is word for word out of Achiever, I really don't have any idea WTF it's talking about.

pauly11235 · Jul 30, 2009

3. the cyclopropene is aromatic because it does not have any sp3 carbons and it follows the 4n +2 rule where n is equal to zero. Aromatic must NOT have any sp3 carbons and by putting a + charge on the top carbon it signifies that it is rather sp2.

Shinpe · Jul 30, 2009

So having a pair of pi electrons is not a definite requirement? although I guess I could see that drawing resonance structures will put that double bond on each bond so it is really shared with all of them.

Thanks

Shinpe · Jul 30, 2009

Sepx said:
1. In question 6's solution it says that osteoblasts deposit Ca2+ in response to Calcitonin's presence. I know Calcitonin lowers blood calcium but I thought it does so by reducing osteoclast activity, confirmed by wikipedia. But does anyone have other resources confirming what Achiever is claiming?

I don't have achiever, i don't understand your other questions, except the bio one and a ochem one.
The stimulus is the raising of Ca in the blood, then thyroid hormone secretes calcitonin. NOW, calicitonin lowers the Ca in two ways, one by increasing deposition of Ca on to bones. Ca deposition on to bones ("making bones") is done by osteoblast, therefore increase osteoblast activity.
Another thing calcinotin does is REDUCING Ca uptake in kidney.

If you have campbell, got to endocrine chapter, look for figure about controling blodd calcium: PTH vs Calcitonin. they are antogonistic.

Ok so this was on my nerve. I found 5-6 places online that said calcitonin decrease blood calcium by inhibiting bone resorption by lowering osteoclast activity. I also went through my old physiology book and it says the same thing. So I'm pretty sure it lowers blood calcium by lowering osteoclast activity. Since bone is constantly being deposited and resorbed, this has the same net effect as depositing calcium from blood onto bones. The Campbell book doesn't say anything about osteoblasts/osteoclasts, just says "calcium deposited onto bone" due to calcitonin, so maybe they just didn't wanna go through that much detail. Well afterall, the exact opposite effect of PTH would be to decrease osteoclast activity, not increase osteoblast activity, per se. Anywayz, I'm kinda convinced that it lowers osteoclast activity, unless you guys have any other resources that say otherwise???

Am I being too anal??? lol

And I guess no one has an answer for that second question yet? I really have zero clue ......

Orgolover · Jul 31, 2009

question 2 solution.
well the question first i guess, cause it was a worded a little funny.

They want to know if 2n = 10, how many different combination of chromosomes can you have in a gamete cell. This is kind of QR related, but not too bad. So if 2n = 10 that means that there are 5 pairs of homologous chromosomes, and when they align, each member of the 5 pairs can go either way; right or left yielding 2 options. since 5 pairs have 2 options each, there are 5^2 possible gamete combinations.

hope this helps.

Shinpe · Jul 31, 2009

Orgolover said:
question 2 solution.
well the question first i guess, cause it was a worded a little funny.

They want to know if 2n = 10, how many different combination of chromosomes can you have in a gamete cell. This is kind of QR related, but not too bad. So if 2n = 10 that means that there are 5 pairs of homologous chromosomes, and when they align, each member of the 5 pairs can go either way; right or left yielding 2 options. since 5 pairs have 2 options each, there are 5^2 possible gamete combinations.

hope this helps.

I trust you meant 2^5 in your last statement, but here comes another question then, wouldn't there be crossing over and all those good stuff happening at prophase I? The 4 chromatids resulting from each chromosome are all different, right? So at the end you have really 4 options for each chromosome, shouldn't that make it 4^5 possible ways???

Orgolover · Jul 31, 2009

Agreed. it is 2^5 ( ... and also 1 am in the morn- forgive me).

I believe there would be crossing over, but it seems that this question seems to ignore that. I thought of it as how many combinations of chromosomes coming from the dad and mom are there. Perhaps its better to think of them like that. So even though there is crossing over, they treat the ones from dad the same, and the ones from mom the same.

ALSO. I recall thinking the same thing and realizing that 32 is the largest option choice they offer. ... so no brainer. Although I do agree with you, crossing over is fun stuff. First time i heard it, i thought of that old show on upn, "crossing over" guy tells over messages to relatives of dead people.
yes. all this goes through my head during topscore exam ! ! !

txchexmex · Jul 31, 2009

For what its worth, Destroyer also says that calcitonin lowers osteoclast activity

Shinpe · Jul 31, 2009

Orgolover said:
Agreed. it is 2^5 ( ... and also 1 am in the morn- forgive me).

I believe there would be crossing over, but it seems that this question seems to ignore that. I thought of it as how many combinations of chromosomes coming from the dad and mom are there. Perhaps its better to think of them like that. So even though there is crossing over, they treat the ones from dad the same, and the ones from mom the same.

ALSO. I recall thinking the same thing and realizing that 32 is the largest option choice they offer. ... so no brainer. Although I do agree with you, crossing over is fun stuff. First time i heard it, i thought of that old show on upn, "crossing over" guy tells over messages to relatives of dead people.
yes. all this goes through my head during topscore exam ! ! !

How I guessed was that it has to have something to do with the haploid number (5) and the only thing out of 2,4,8,16,32 that has anything to do with 5 is 32. I hope actual DAT questions are this easy to guess lol.

But yea I think if a question like this came up on the test, it should really be 4^5, crossing over doesn't like to be taken lightly ;p

Shinpe · Jul 31, 2009

txchexmex said:
For what its worth, Destroyer also says that calcitonin lowers osteoclast activity

So that's where else I had seen it lol. I also asked my friend and she looked it up in her endocrinology book and confirmed this, that's why it's used as a drug against osteoporosis.

Orgolover · Sep 4, 2009

girls are icky... don't trust them.

Questions from Achiever 1

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