Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What is the main purpose of chloroplasts within leaf cells?

1. Photosynthesis

2. Storage

3. Gas exchange

4. Support

The correct answer is: Photosynthesis

Chloroplasts are organelles found in the cells of green plants and some algae, and their primary function is photosynthesis. During this process, chloroplasts capture light energy, usually from the sun, and convert it into chemical energy stored in glucose. This is crucial for the plant's ability to produce its own food, which also provides energy for other organisms in the ecosystem when they consume the plant. While chloroplasts play a central role in photosynthesis, other options pertain to different functions within the plant. For instance, storage typically refers to organelles like vacuoles, which store nutrients, waste products, and other substances. Gas exchange is facilitated by structures such as stomata, which allow for the intake of carbon dioxide and the release of oxygen, but this does not involve chloroplasts directly. Support functions in plants are primarily handled by cell walls and structures like xylem and phloem rather than chloroplasts. Therefore, the main purpose of chloroplasts is indeed to carry out photosynthesis, making it the most accurate choice.