Priority 1: The equation

carbon dioxide + water → glucose + oxygen (light energy absorbed by chlorophyll). Know this in words and balanced symbols: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Remember: this is an endothermic reaction: light energy is converted to chemical energy stored in glucose.

Priority 2: Limiting factors

Three factors can limit the rate of photosynthesis: light intensity, CO₂ concentration, and temperature. On a graph, the rate increases with the factor until a plateau: at the plateau, another factor has become limiting. Be able to identify which factor is limiting from a graph and suggest what it might be.

Priority 3: Leaf adaptations

Know the structure of a leaf cross-section: upper epidermis, palisade mesophyll (tightly packed, many chloroplasts: main site of photosynthesis), spongy mesophyll (air spaces for gas exchange), lower epidermis with stomata (allow CO₂ in and O₂ out), guard cells (control stomatal opening).

Priority 4: Uses of glucose

Plants use glucose for: respiration (energy release), conversion to starch (storage), conversion to cellulose (cell walls), making amino acids (with nitrate ions) for protein synthesis, making fats and oils (lipids for storage).