Q24

[zhangstagangsta]

This was a tough passage, and for this question, I was stuck between B and D. Could someone explain why D is the right answer is B is the wrong one?

[ManhattanPrepLSAT1]

I agree that this is a tough science passage, and the tricky thing is that during the first paragraph, we aren't given a clue to the technical information that is awaiting us in paragraphs two and three.

The easy answer to why answer choice (B) is incorrect is that answer choice (B) claims that the passage asserts that other atmospheric gases other than oxygen interfere with photosynthesis. Unfortunately, no where in the passage does the author ever discuss other gases interfering with the photosynthesis process. The passage does mention that other gases are brought in to the plant, but go back and read paragraph two where the author talks about the interference of photosynthesis in lines (30-35). Only oxygen is mentioned.

Between lines (45-47) the author mentions that oxygen and other atmospheric gases are held away from the enzyme Rubisco, and this is why C-4 plants are able to avoid the troubles mentioned towards the end of paragraph two, and why C-4 plants are so successful.

Hope this helps.

[cyruswhittaker]

So is D right because of the mechanism at play? The gases are excluded from the cells, so in order to enter the cells (50-54), carbon dioxide turn into an intermediary, nongas C-4 molecule that can enter the cells, allowing for the production of sugargs.

[interestedintacos]

By mentioning all atmospheric gases, and not just oxygen, which is all that was mentioned up to this point, the author is helping us understand why, as we learn later, carbon dioxide turns into a nongas molecule, and how this is part of the C-4 process (and where it derives its name).

You have to think about it this way. Up until that point we were only talking about oxygen. So why would it be relevant to mention that all other atmospheric gases are excluded as well? That information isn't relevant to the oxygen issue, so the author's reference to it seems merely like extra/unnecessary info. But then when we learn that carbon dioxide has to convert into a nongas molecule it should be obvious that the information was included to help explain why this fundamental part of the C-4 process happens.

[ManhattanPrepLSAT1]

nice work interestedintacos! A bit like forshadowing, right? Otherwise why talk about "atmospheric gasses?"

We could also think about the following analogy: The guards were standing at the gate. So upon arrival the investigators pulled out there identification badges.

If you think about the role of the claim that "The guards were standing at the gate," it's there to explain why the investigators did what they did - took out their badges. It's something that we know to be true, that might help explain how/why something else we observed happened.

What do you think?