Overview
This lecture explains the process of photosynthesis in plants, detailing where it occurs, the chemical equation, and how plants use glucose produced.
Photosynthesis Process
- Photosynthesis occurs in the leaves of plants, specifically in chloroplasts.
- Chloroplasts contain chlorophyll, a pigment that absorbs light energy.
- Light energy is used to convert carbon dioxide and water into glucose and oxygen.
- The balanced chemical equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (with light energy).
- The process is endothermic, meaning it requires energy from the environment (light).
Reactants and Products in Photosynthesis
- Carbon dioxide enters leaves through the stomata by diffusion.
- Water is absorbed from the soil by roots and transported via xylem to leaves.
- Glucose is the main product; oxygen is released as a by-product.
Uses of Glucose in Plants
- Glucose is used in respiration to release energy.
- Glucose molecules combine to form cellulose, which strengthens plant cell walls.
- Excess glucose is stored as starch; starch is compact and insoluble for long-term storage.
- Glucose combines with nitrate ions from soil to make amino acids and then proteins.
- Glucose is also used to make oils and fats, stored mainly in seeds for future energy.
Factors Affecting Photosynthesis
- The rate of photosynthesis depends on light intensity, temperature, carbon dioxide concentration, and chlorophyll amount.
Key Terms & Definitions
- Chloroplast — Subcellular structure in plant cells where photosynthesis occurs.
- Chlorophyll — Green pigment in chloroplasts that absorbs light energy.
- Photosynthesis — Light-driven process converting CO₂ and H₂O into glucose and O₂.
- Endothermic reaction — A reaction that absorbs energy from its surroundings.
- Stomata — Pores on leaf surfaces that allow gas exchange.
- Xylem — Tissue that transports water from roots to leaves.
- Cellulose — Complex carbohydrate made from glucose, forms plant cell walls.
- Starch — Storage form of glucose in plants, insoluble and compact.
Action Items / Next Steps
- Review factors affecting the rate of photosynthesis: light, temperature, CO₂ concentration, and chlorophyll.
- Prepare for next lesson on how these factors influence photosynthesis rates.