OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What type of reaction is photosynthesis classified as?

1. Exothermic

2. Endothermic

3. Catalytic

4. Thermodynamic

The correct answer is: Endothermic

Photosynthesis is classified as an endothermic reaction because it requires energy input in the form of sunlight to occur. During photosynthesis, plants absorb light energy from the sun, which is then used to convert carbon dioxide and water into glucose and oxygen. This process involves the formation of chemical bonds that store energy in the glucose molecules, making it an energy-storing process. In contrast, exothermic reactions release energy, often in the form of heat, during the reaction. Catalytic reactions involve a catalyst to speed up the process without being consumed in the reaction, while thermodynamic refers to the study of energy and work in chemical processes, rather than classifying the reaction itself. Thus, photosynthesis distinctly fits into the category of endothermic reactions due to its energy absorption and conversion nature.