Overview
This lecture explains the process of photosynthesis in plants, its chemical equation, where it occurs, and how plants use glucose produced from photosynthesis.
Photosynthesis Process
- Photosynthesis enables plants to convert carbon dioxide and water into glucose and oxygen using light energy.
- This process occurs in the leaves, specifically in chloroplasts containing the pigment chlorophyll.
- Chlorophyll absorbs light energy, which drives the reaction that forms glucose and oxygen.
- The chemical equation for photosynthesis is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (with light energy above the arrow).
- Photosynthesis is an endothermic reaction, meaning it absorbs energy from the environment.
Reactants and Their Sources
- Carbon dioxide enters leaves via stomata by diffusion.
- Water is absorbed from soil by roots and transported to leaves through xylem vessels.
- Light provides the necessary energy for the reaction.
Products and Uses of Glucose
- Main useful product for plants is glucose; oxygen produced is often a byproduct.
- Glucose is used in cellular respiration to release energy for plant cells.
- Glucose molecules combine to form cellulose (for cell walls) and starch (for energy storage).
- Starch is a compact, insoluble form suitable for long-term storage in cells.
- Glucose combines with nitrate ions from the soil to make amino acids, which build proteins.
- Glucose is also converted into oils and fats for future energy needs, especially in seeds.
Photosynthesis and Plant Growth
- Plant growth rate depends on the rate of photosynthesis.
- Factors affecting the rate include light intensity, temperature, carbon dioxide concentration, and chlorophyll amount.
Key Terms & Definitions
- Photosynthesis — Process where plants make glucose and oxygen from carbon dioxide and water using light energy.
- Chloroplasts — Subcellular structures in plant leaves where photosynthesis occurs.
- Chlorophyll — Pigment in chloroplasts that absorbs light energy for photosynthesis.
- Endothermic Reaction — A reaction that absorbs energy from the surroundings.
- Cellulose — Complex carbohydrate forming plant cell walls.
- Starch — Storage form of glucose in plants, compact and insoluble.
- Amino Acids — Building blocks of proteins, made from glucose and nitrate ions.
Action Items / Next Steps
- Review the factors affecting the rate of photosynthesis.
- Prepare for questions on the uses of glucose in plants.