PT122.S3.P4.Q21 > Analytics

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Every culture that has adopted the cultivation of maize—also known as corn—has been radically changed by it. ███

intro topic · Influence of maize

explain significance · of maize

Contributed to development of agrarian and urban societies, and European population growth

hypothesis · Maize's influence is due to its productivity

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phenomenon · Productivity of maize

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Intro to hypothesis · Biochemistry provides the answer

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Context · Explanation of photosynthesis

Water splits into hydrogen and oxygen, hydrogen produces energy. Meanwhile, carbon dioxide builds sugars with help from enzyme (rubisco).

Problem · Too much oxygen interferes with photosynthesis

Enzyme supposed to work with carbon dioxide, but oxygen binds to enzyme instead, meaning less enzyme available to work with carbon dioxide

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Solution (hypothesis) · Different method of photosynthesis

Enzyme (rubisco) is kept separate from atmospheric gases (e.g., oxygen and carbon dioxide)

Complication with hypothesis · Carbon dioxide cannot reach enzyme as gas

Solution: Carbon dioxide becomes nongas molecule (C-4) in order to reach enzyme and drive photosynthesis

Strengthen hypothesis · Other highly productive crops use this method of photosynthesis

Passage Style

Phenomenon-hypothesis (RC)

Single position

21.

Which one of the following ████ ██████████ ██████ ███ ████ █████ ██ ███ ████████

Question Type

Main point

The main point of this Phenomenon-Hypothesis passage is the author’s explanation for why maize is so productive: it uses C-4 photosynthesis, which separates oxygen gas from the rubisco enzyme, thereby preventing oxygen from interfering with photosynthesis.

The greater productivity ██ ██████ ██ ████████ ████ ████ █████ ██████ ██ ███ ██ ███ ███ ██████████████ ████████ ██ █████ ███ █████████ ████ █████ ██████ ███ █████████ ████ ███ ███████ ██ ██████ ███████

This is an accurate summary of the main point. P2 introduces a constraint that most crops have (the reactions that build sugars are hindered by excess oxygen), and the author spends the rest of the passage explaining how the C-4 process allows maize to be more productive than those crops.

70%

Because of their ███████ ██ ███████ ███████ ██████████ ███ ██████ █████████ ██ ██████████ █████ ███████ █████████ ██████ ████ ███ █ ███ ██████████████ ███████ ████ ██████ ██ █████ ███ ███████████ ██ ████ █████ █████████

Unsupported. Although the author states that C-4 plants are more productive, she never suggests that their nutrients are of higher quality than any other plant’s.

12%

C-4 photosynthesis, which ██████ ██ ██████ ████████ █ ███████ ████████ ██ ████████ █████████ ████ █████ ████ █████████ ███ ██ █████████ ███████████ ████████ ████ ██ ██████████████ █████████ ██ ███████ ███████

Unsupported. C-4 photosynthesis makes more efficient use of the enzyme rubisco, not atmospheric hydrogen.

The presence of ███ ██████ ███████ ██ █ ███ ██████ ██ ███ ███████ ██ ███ ███████ █████████ ██████ ██ ██████████ ███ ████████ ███████ ██ █████ ████ ██ ██████ ██ ███ ██████████ ██ ██████ ██ ███████████████

Anti-supported. Rubisco isn’t what helps C-4 plants to circumvent any negative effects; rubisco is the target of those negative effects. Those negative effects are circumvented in C-4 plants by the process of separating rubisco from oxygen.

Some of the ███████ ████ ██████████ ████ ███████ █████████ ██████ ████ ███████ ████████ █████████ ██████████ ██ ███████ ███████████ █████ ████ █████ ████ █████████████ ██ ███████ ████ ████████ ███ ███████ ███████

This (inaccurately) describes how the mechanism works, but the main point isn’t simply that some productive crops have this mechanism—it’s that this mechanism is precisely what allows these crops to be so productive. And (E)’s description of the C-4 mechanism is wrong, anyway; atmospheric gases still enter the leaves. The oxygen within the leaf is just kept separate from rubisco.

13%

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PrepTest 122 - Section 3 - Passage 4 - Question 21

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PrepTest 122 - Section 3 - Passage 4 - Question 21

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