What is photosynthesis? Explain it with a balanced equation, and describe how stomata open and close.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define in one line. Photosynthesis is the process by which green plants make carbohydrate from carbon dioxide and water, using light absorbed by chlorophyll, and give out oxygen.
2 · Write the balanced equation. 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O, with sunlight and chlorophyll written over the arrow.
3 · List the three events.
Chlorophyll absorbs light energy.
Light energy becomes chemical energy; water splits into hydrogen and oxygen.
Carbon dioxide is reduced to carbohydrate, stored as starch.
4 · Explain stomata. Guard cells swell when water enters, so the pore opens; they shrink when water leaves, so the pore closes.
5 · Draw open and closed stomata. [Diagram: guard cells, stomatal pore, chloroplasts, nucleus, epidermal cells]
6 · Link to daily life. All the food we eat, from rice to vegetables, comes from photosynthesis, which also refills the oxygen in the air.
7 · Close in one line. So photosynthesis turns light energy into the chemical energy stored in food.
Scoring tip: Write the equation exactly, with the conditions over the arrow. The balanced equation and a labelled stoma each earn a mark.
