Histadine

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Histadine

by ssgmatter » Thu May 13, 2010 6:46 am
A certain cultivated herb is one of a group of closely related plants that thrive in soil
with high concentrations of metals that are toxic to most other plants. Agronomists
studying the herb have discovered that it produces large amounts of histidine, an
amino acid that, in test-tube solutions, renders these metals chemically inert. Possibly,
therefore, the herb's high histidine production is what allows it to grow in metal-rich
soils, a hypothesis that would gain support if ______.
A. histidine is found in all parts of the plant-roots, stem, leaves, and flowers
B. the herb's high level of histidine production is found to be associated with an
unusually low level of production of other amino acids
C. others of the closely related group of plants are also found to produce histidine
in large quantities
D. cultivation of the herb in soil with high concentrations of the metals will, over
an extended period, make the soil suitable for plants to which the metals are
toxic
E. the concentration of histidine in the growing herb declines as the plant
approaches maturity

Guys please explain this one with some good reasons.....
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by Domnu » Thu May 13, 2010 6:52 am
IMO, [spoiler]C

A - out of scope... this might not have to be true for the plant to survive.
B - out of scope.
C - true... if other related plants which can survive in the soil have histidine in large quantities, we have reason to believe the hypothesis
D - not necessarily true... for this to hold, we would have to assume that the histidine spreads through the soil, which isn't stated anywhere.
E - not necessarily true... how do we know that the plant doesn't constantly produce histidine?
[/spoiler]
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by ssgmatter » Thu May 13, 2010 7:25 am
I am really confused in deciding between C and D here......Rest I can eliminate

Any thoughts?
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by paes » Thu May 13, 2010 9:35 pm
ssgmatter wrote:I am really confused in deciding between C and D here......Rest I can eliminate

Any thoughts?
IMO D

Conclusion : he herb’s high histidine production is what allows it to grow in metal-rich
soils

C does not link histidine to toxic metals.

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by kevincanspain » Fri May 14, 2010 2:55 am
ssgmatter wrote:A certain cultivated herb is one of a group of closely related plants that thrive in soil
with high concentrations of metals that are toxic to most other plants. Agronomists
studying the herb have discovered that it produces large amounts of histidine, an
amino acid that, in test-tube solutions, renders these metals chemically inert. Possibly,
therefore, the herb's high histidine production is what allows it to grow in metal-rich
soils, a hypothesis that would gain support if ______.
A. histidine is found in all parts of the plant-roots, stem, leaves, and flowers
B. the herb's high level of histidine production is found to be associated with an
unusually low level of production of other amino acids
C. others of the closely related group of plants are also found to produce histidine
in large quantities
D. cultivation of the herb in soil with high concentrations of the metals will, over
an extended period, make the soil suitable for plants to which the metals are
toxic
E. the concentration of histidine in the growing herb declines as the plant
approaches maturity

Guys please explain this one with some good reasons.....
If it neutralizes the toxic metals, other plants should be able to grow in this soil.
The existence of other plants with this property does nothing to support the claim that this property allows the plant to grow in this soil.

Answer D
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by Domnu » Fri May 14, 2010 4:33 am
Hi Kevin,

How do you know that the histidine doesn't stay contained within the plant, rendering the metals chemically inert?

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by bupbebeo » Sat May 15, 2010 2:52 am
kevincanspain wrote:
ssgmatter wrote:A certain cultivated herb is one of a group of closely related plants that thrive in soil
with high concentrations of metals that are toxic to most other plants. Agronomists
studying the herb have discovered that it produces large amounts of histidine, an
amino acid that, in test-tube solutions, renders these metals chemically inert. Possibly,
therefore, the herb's high histidine production is what allows it to grow in metal-rich
soils, a hypothesis that would gain support if ______.
A. histidine is found in all parts of the plant-roots, stem, leaves, and flowers
B. the herb's high level of histidine production is found to be associated with an
unusually low level of production of other amino acids
C. others of the closely related group of plants are also found to produce histidine
in large quantities
D. cultivation of the herb in soil with high concentrations of the metals will, over
an extended period, make the soil suitable for plants to which the metals are
toxic
E. the concentration of histidine in the growing herb declines as the plant
approaches maturity

Guys please explain this one with some good reasons.....
If it neutralizes the toxic metals, other plants should be able to grow in this soil.
The existence of other plants with this property does nothing to support the claim that this property allows the plant to grow in this soil.

Answer D

hey kevincanspain, answer D, show another reason why this herb can thrive in this region without secreting the chemical. therefore, it weakens the argument. How it can be a correct answer.


Please post OA, the poster.

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by bupbebeo » Sat May 15, 2010 3:02 am
what is the problem with my reasoning if i sasy

the herb thrives and secretes a chemical.

other plants also thrive and secretes the same chemical

therefore, the chemical seems to be the factor that helps the herb thrive.

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by mohit11 » Sat May 15, 2010 4:39 am
Hi Kevin,

Would request you to refer to https://www.beatthegmat.com/herb-t49523.html (reply by Eli Meyer, Kaplan GMAT Teacher). According to her answer should be C

This is her take on the Issue - "In this case, the possible cause is Histidine, leading to the effect of survival of the plant. But there is another key clue in this stimulus--that this herb is one of a family of herbs. That is a shift in scope, which indicates an assumption in the argument. The correct answer, we can predict, must therefore establish whether histidine is a possible explanation for not only the one herb but also its cousins, or whether something else about the family of plants aside from histidine is a likely cause.

For that reason, C will help us. If all of the family produces histidine, and all live in metal-rich soil, our explanation is highly plausible. However, if some of the species are living in the same toxic soil without histidine, the claim that this one plant requires the amino acid becomes suspect."


Anyways, C was my choice too for the same reasons outlined above. Would love to hear your take on this one.


PS: I Googled this question, OA given in various forums is neither C nor D . OA is E :)

Reasons why E is correct : "Yes, strengthens the argument. It implies that the plant has been producing histidine for a long time, to nullify the metallic affect, and hence as the plant reaches maturity, the plant's production of histidine has decreased.

If histidine weren't the cause for nullifying metallic affect, the plant would still be capable of producing large amount of histidine even when it is mature"

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by harshavardhanc » Sat May 15, 2010 4:42 am
Domnu wrote:Hi Kevin,

How do you know that the histidine doesn't stay contained within the plant, rendering the metals chemically inert?

Domnu
agree with Domnu. The stimulus gives us no clues about the place where reactions, similar to those in labs, occur in plants. If they're outside plants, then D may support. But, in this case, nothing can be said for sure.

However, the conclusion is that Histidine allows the plant to grow in such conditions.

the stimulus says that this herb is one of many plants which grow in such soils. So, if the total group produces Histidine, then the conclusion gets a support that it is Histidine which is helping them to survive.


IMO C.
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by harshavardhanc » Sat May 15, 2010 4:51 am
mohit11 wrote:
Reasons why E is correct : "Yes, strengthens the argument. It implies that the plant has been producing histidine for a long time, to nullify the metallic affect, and hence as the plant reaches maturity, the plant's production of histidine has decreased.

If histidine weren't the cause for nullifying metallic affect, the plant would still be capable of producing large amount of histidine even when it is mature"
the stimulus doesn't tell that a plant comes with a fixed bundle of Histidine. So, I don't think E can be the correct one....

i may be wrong, but still .....
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by mohit11 » Sat May 15, 2010 4:56 am
harshavardhanc wrote:
mohit11 wrote:
Reasons why E is correct : "Yes, strengthens the argument. It implies that the plant has been producing histidine for a long time, to nullify the metallic affect, and hence as the plant reaches maturity, the plant's production of histidine has decreased.

If histidine weren't the cause for nullifying metallic affect, the plant would still be capable of producing large amount of histidine even when it is mature"
the stimulus doesn't tell that a plant comes with a fixed bundle of Histidine. So, I don't think E can be the correct one....

i may be wrong, but still .....
I am with you on C. I was just trying to find the correct answer. So was presenting different point of views. Apparently, the OA is E.

It would be great if the original poster can tell us the source of the question.

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by kevincanspain » Sat May 15, 2010 8:02 am
Here's why I would not choose C

We are told that these herbs are closely related, so it seems likely that they all produce histidine. Thus C seems to give us more of the same evidence.

Imagine that non-feeling creatures from outer space saw that the Spanish Earthlings they observed have emotions as well as hearts and often refer to their emotional state by using expressions that include the word 'heart'. Their hypothesis that human emotions are caused by the heart would not be substantially supported by further evidence that all humans have hearts and emotions, but of course, their hypothesis would be suspect if there were heartless feeling people.

Here's why I would not choose E. Maturity does not equal death, at least I hope not! Many plants (trees for example) live many years beyond maturity. So will a certain GMAT instructor...

D seems to be a logical consequence of the hypothesis if it were indeed true. If the plants secrete an enzyme that 'kills' the metal in a test tube and this is the mechanism that allows them to thrive in a field, then other plants should be able to grow after the metal in a field has been 'killed' by histidine. This shows that the plant actually neutralizes the metal; it is not just a question of immunity. We also see that the what happened in the test tube actually happens in real life! What happens in a test tube does not always predict what happens in real life, nor we were given information about the quantity or concentration of histidine used in the test tube in which the metal was rendered inert (i.e. non-reactive)

If we could genetically engineer other plants to produce histidine, then they should be able to survive in such fields. D doesn't say that, of course, but if these other plants are given the benefits that come with histidine production regarding this metal, it make sense that they should live. If they didn't, I would not believe the hypothesis
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by harshavardhanc » Sat May 15, 2010 12:36 pm
kevincanspain wrote: We are told that these herbs are closely related, so it seems likely that they all produce histidine. Thus C seems to give us more of the same evidence.
Assumption 1: "closely related " stretched too much.

Humans and chimps are closely related. Do we put all our limbs on the ground while walking? Similarly, it cannot be assumed that resemblance MUST be on the histidine front.
kevincanspain wrote: D seems to be a logical consequence of the hypothesis if it were indeed true. If the plants secrete an enzyme that 'kills' the metal in a test tube and
Assumption 2: Stimulus says that these plants produce histidine. it never says that they secret this enzyme.

Humans too produce enzymes, but will it be logical to conclude that humans secret all the enzymes after production?

I'm still with C

Phil, can we have the OA now?
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by kevincanspain » Sat May 15, 2010 1:45 pm
Note as well that C says others, not all others.

Does the plant survive by producing a chemical that renders the metal inert? Can we extrapolate what happens in a test tube to an actual field? Was the amount of histidine added to the test tube realistic? If so, D should be true.

D, if true, provides evidence that the mechanism by which this plant survives is by rendering the metal inert. It's not that the metal has no effect on the plant: the plant actually produces a chemical that deprives the metal of its destructive properties. I think that the hypothesis would lose credibility if D were not true.

C would be MUCH more convincing if it said that plants outside this group that cannot survive do not produce histidine. If the plants are closely related, I don't find it far-fetched to suspect that many of them produce histidine.

I fear we will never get an offical answer for this question, as no one has ever said that it is from GMATPrep or an OG or even a test-prep company
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