⚡ Quick Revision: Photosynthesis
Photosynthesis is the process by which green plants prepare their own food (glucose) using carbon dioxide and water in the presence of sunlight and chlorophyll.
The Chemical Equation
Requirements for Photosynthesis
- 1 Chlorophyll: Green pigment in chloroplasts that traps solar energy.
- 2 Sunlight: The ultimate source of energy for the process.
- 3 Carbon Dioxide: Enters the leaf through stomata from the atmosphere.
- 4 Water: Absorbed by roots from the soil and transported via xylem.
⚡ Quick Revision: Factors and Leaf Adaptations
The rate of photosynthesis is not constant; it changes based on environmental conditions and the structural efficiency of the leaf.
External Factors Affecting the Rate
- ✔ Light Intensity: Rate increases with light intensity up to a certain point.
- ✔ CO₂ Concentration: Higher CO₂ levels generally increase the rate of food production.
- ✔ Temperature: Optimum temperature is usually between 25°C to 35°C. Extremely high temperatures can damage enzymes.
Leaf Adaptations
Leaves are often called the "Food Factories" of the plant because of these features:
- ✔ Large Surface Area: To absorb maximum sunlight.
- ✔ Stomata: Numerous tiny pores on the lower surface for gas exchange.
- ✔ Thinness: Reduces the distance CO₂ has to travel to reach the cells.
⚡ Quick Revision: Respiration in Plants
Respiration is a chemical process where glucose is broken down to release energy (ATP). Unlike photosynthesis, respiration occurs 24 hours a day in all living cells.
Aerobic vs. Anaerobic Respiration
| Feature | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen | Occurs in presence of O₂. | Occurs in absence of O₂. |
| Energy | High energy (38 ATP). | Low energy (2 ATP). |
| Products | CO₂, Water, Energy. | Ethanol/Lactic acid, CO₂, Energy. |
The Aerobic Equation
Plants breathe through Stomata (leaves), Lenticels (old woody stems), and General Surface (roots).
⚡ Quick Revision: Photosynthesis vs. Respiration
These two processes are opposite in nature. While photosynthesis stores energy in the form of food, respiration releases that energy for the plant's use.
Comparison Table
| Feature | Photosynthesis | Respiration |
|---|---|---|
| Function | Food synthesis (Anabolic). | Food breakdown (Catabolic). |
| Time | Only in daylight. | All the time (Day & Night). |
| Location | Only in cells with Chlorophyll. | In all living cells. |
| Gas Exchange | Takes CO₂, Releases O₂. | Takes O₂, Releases CO₂. |
| Energy | Energy is stored. | Energy is released (as ATP). |
During the day, the rate of photosynthesis is much higher than respiration, so plants give out more oxygen. At night, since photosynthesis stops, they only release carbon dioxide.