Photosynthesis:
- Plants make their own food by photosynthesis.
- Photosynthesis is the process by which plants synthesise carbohydrates from raw materials using energy from sunlight.
- The raw materials required for photosynthesis are carbon dioxide and water, where carbon dioxide is taken in by the leaves and water is taken in through the roots to the leaves.
- During this process, glucose and oxygen are produced in the presence of sunlight and chlorophyll(found in leaves).
  - Glucose produced is used by plants in various ways.
  - Oxygen is released into the surrounding area through the leaves.
Word equation for photosynthesis:
- Carbon dioxide + Water → Glucose + Oxygen in the presence of light and chlorophyll

Balanced chemical equation for photosynthesis:
- 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Chlorophyll:
- Chlorophyll is a green pigment found in the chloroplast present in plant cells.
- It is used to absorb light energy from the sun.
- Chlorophyll transfers light energy into chemical energy in molecules, for the synthesis of carbohydrates (glucose).

Subsequent use and storage of the carbohydrates made in photosynthesis:
- Starch as an energy store:
  - Excess glucose is converted to sucrose, which is further converted to starch.
  - Hence, glucose is stored in the plant as starch.
- Cellulose to build cell walls:
  - Glucose is also used for the synthesis of cellulose cell walls.
- Glucose used in respiration to provide energy:
  - Glucose is used by plant cells in respiration to provide energy for cellular activities.
- Sucrose for transport in the phloem:
  - Excess glucose is converted into sucrose.
  - Sucrose is transported through the phloem to storage organs, for example, seeds, stems and roots.
- Nectar to attract insects for pollination:
  - Glucose can also be converted into nectar in flowers.
  - Nectar is the sweet flower juice produced by nectaries present in flowers to attract insects for pollination.
- Proteins to form protoplasm:
  - Glucose in the leaves reacts with nitrates to form amino acids.
  - These amino acids combine to form proteins, which can be converted into new protoplasm within the cells.
- Fats for cellular respiration:
  - Glucose can also be converted and stored as fats.
  - Fats may be used in cellular respiration or as a component of the cell surface membrane.

13.02 - Photosynthesis

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