Biology Regents Practice Exam

In photosynthesis, plants convert carbon dioxide and water into which substance?

1. Glucose

2. Oxygen

3. Starch

4. Cellulose

The correct answer is: Glucose

During photosynthesis, plants use sunlight to convert carbon dioxide and water into glucose, a simple sugar that serves as an essential source of energy for the plant. The process occurs primarily in the chloroplasts, where chlorophyll captures sunlight and initiates the conversion of these raw materials. The overall chemical reaction can be summarized as: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 In this equation, glucose (C6H12O6) is the primary product, while oxygen (O2) is released as a byproduct. Glucose is crucial for the plant, as it can be used immediately for energy or stored as starch for later use. It is also a fundamental building block for other organic molecules and compounds in plants, playing a key role in growth and metabolism. While starch and cellulose are important substances derived from glucose, they are not the direct products of photosynthesis. They represent forms of stored energy or structural components, respectively, but glucose itself is the main substance synthesized during this vital biological process.