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

What are the main stages of photosynthesis?

1. Oxygen production followed by nutrient synthesis

2. Light absorption, water splitting, and glucose formation

3. Carbon fixation followed by oxygen release

4. Glucose synthesis and respiration

The correct answer is: Light absorption, water splitting, and glucose formation

The main stages of photosynthesis include light absorption, water splitting, and glucose formation. In the first stage, plants use chlorophyll to absorb light energy, primarily from the sun. This energy is essential for driving the subsequent reactions. The second stage involves splitting water molecules (a process called photolysis), which not only helps to release oxygen as a byproduct but also provides electrons and protons needed for the synthesis of glucose. Lastly, during the light-independent reactions, often referred to as the Calvin cycle, carbon dioxide is fixed and converted into glucose using the energy from ATP and NADPH generated in the first stage. This comprehensive process allows plants to convert light energy into chemical energy stored in sugars, which are crucial for their growth and energy needs.