Question 4·Easy·Rhetorical Synthesis
While researching a topic, a student has taken the following notes:
- Passive transport moves substances across cell membranes without energy input.
- Passive transport moves substances down their concentration gradients.
- Active transport requires cellular energy (ATP).
- Active transport can move substances against their concentration gradients.
The student wants to contrast passive and active transport. Which choice most effectively uses relevant information from the notes to accomplish this goal?
For rhetorical synthesis questions using notes, first underline the task word (here, “contrast”) to know what relationship you must show. Then quickly list the key points from the notes for each item (e.g., passive vs. active transport) and identify the most important differences or similarities. Next, scan the answer choices and immediately eliminate any that: (1) ignore one side of the contrast, (2) leave out a crucial idea from the notes, or (3) add information not supported by the notes. Choose the sentence that uses multiple relevant details and clearly matches the required relationship (contrast, cause-effect, etc.) in a single, clear statement.
Hints
Focus on the word "contrast"
The question asks for a sentence that contrasts passive and active transport. Look for an option that clearly shows how the two are different, not just that they both exist.
Use the notes to find the main differences
From the notes, identify two ways passive and active transport differ. Think about what the notes say about energy and about concentration gradients for each type.
Check that both sides are covered
Eliminate any choice that talks about only one type of transport or that fails to mention the main differences you found in the notes. The best choice should describe both processes and highlight how they differ in both key ways.
Step-by-step Explanation
Identify the task: contrast the two processes
The question says the student wants to contrast passive and active transport.
That means the best sentence must:
- Mention both passive and active transport, and
- Clearly show how they are different, not just that they both exist or are used by cells.
Pull out the key contrasting details from the notes
Look at what the notes say about passive transport:
- It moves substances across cell membranes without energy input.
- It moves substances down their concentration gradients.
Now look at what the notes say about active transport:
- It requires cellular energy (ATP).
- It can move substances against their concentration gradients.
So there are two main differences:
- Whether or not energy is used.
- Whether substances move down or against their concentration gradients.
Decide what a good contrasting sentence must include
A strong contrasting sentence should:
- Include both passive and active transport in one sentence.
- Use both key differences from the notes: energy use and direction of movement along the concentration gradient.
- Use contrasting language (such as “whereas” or similar) to make the difference clear.
Keep this checklist in mind as you evaluate the answer choices.
Check each answer against the checklist
Now compare each option to what we need:
- A) Mentions both types but only says cells rely on them. It does not explain how they differ (no mention of energy or gradients), so it does not truly contrast them.
- B) Gives one fact about active transport (needs energy) and one fact about passive transport (down their gradients), but it leaves out that passive uses no energy and that active can go against gradients. The contrast is incomplete.
- D) Only talks about passive transport. It doesn’t mention active transport at all, so there is no contrast.
C is the only choice that:
- Mentions both passive and active transport,
- States that passive transport moves substances down their concentration gradients without energy, and
- States that active transport uses energy to move substances against gradients,
- And uses “whereas” to show the contrast.
Therefore, the correct answer is:
C) Passive transport moves substances down their concentration gradients without energy, whereas active transport uses energy to move substances against gradients.