ACT (Enhanced)ReadingEasy
Read the following excerpt from a science textbook: "Photosynthesis, the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll, is fundamental to most life on Earth. It converts light energy into chemical energy, which is then stored in organic compounds like glucose. This complex biochemical pathway involves two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). During the light-dependent reactions, water is split, releasing oxygen, and energy-carrying molecules (ATP and NADPH) are produced. These molecules then power the light-independent reactions, where carbon dioxide is fixed into sugars." Which of the following best describes the primary function of chlorophyll in photosynthesis?
- ATo store chemical energy in organic compounds.
- BTo convert carbon dioxide into sugars.
- CTo split water molecules, releasing oxygen.
- DTo absorb light energy for the synthesis of food.
Show answer & explanationAnswer & explanation
Correct answer: D. To absorb light energy for the synthesis of food.
The text explicitly states that photosynthesis uses sunlight to synthesize foods 'with the help of chlorophyll.' It further clarifies that the process 'converts light energy into chemical energy.' Therefore, chlorophyll's primary role is light absorption.
Why the other options are wrong
- A. Storing chemical energy in organic compounds like glucose is the ultimate outcome of photosynthesis, not the primary function of chlorophyll.
- B. Converting carbon dioxide into sugars occurs during the light-independent reactions (Calvin cycle) and is powered by ATP and NADPH, not directly by chlorophyll.
- C. Splitting water molecules is a part of the light-dependent reactions, but it is not the primary function of chlorophyll itself.
Primary Function
The main or most important role or purpose of a component, process, or concept as described in a text.
- Identifies the central task or contribution.
- Often stated directly or strongly implied early in the description.
- Distinguishes core purpose from secondary effects or related steps.
Memory trick: Focus on the 'why' and 'what it does first' to find the primary function.