Key Stage 3 (KS3) General Knowledge Test 2025 – 400 Free Practice Questions to Pass the Exam

The process by which plants make their food is called photosynthesis. During photosynthesis, plants use sunlight, carbon dioxide from the air, and water from the soil to produce glucose, a type of sugar that serves as food for the plant. This process occurs mainly in the leaves, where chlorophyll (the green pigment) captures light energy. The overall chemical reaction can be summarized as:

6CO₂ (carbon dioxide) + 6H₂O (water) + light energy → C₆H₁₂O₆ (glucose) + 6O₂ (oxygen).

Photosynthesis not only provides nourishment for the plants themselves but also releases oxygen into the atmosphere, which is essential for the survival of most living organisms on Earth.

In contrast, respiration is a process that organisms (including plants) use to convert glucose into energy, and fermentation is a different metabolic process that occurs in the absence of oxygen. Digestion is a process that takes place primarily in animals, breaking down food into smaller molecules for absorption. Thus, photosynthesis is unique to plants and crucial for their energy production.