Photosynthesis
Subject: Science (Biology) | Topic: Photosynthesis
For TLT, ECT, PST, JEST & All Competitive Exams
All living things need energy to survive, and while animals get this energy by eating food, green plants make their own food using sunlight. This process is called Photosynthesis, and it is the foundation of almost all life on Earth, since it is the source of both food and oxygen for most living organisms. This topic is a core, frequently tested area of Biology in TLT, ECT, PST, and JEST exams.
What is Photosynthesis?
Photosynthesis is the process by which green plants, algae, and some bacteria make their own food (glucose) using carbon dioxide, water, and sunlight, with the help of a green pigment called chlorophyll. It takes place mainly in the leaves of plants, inside cell organelles called chloroplasts.
The Photosynthesis Equation
The overall chemical reaction of photosynthesis can be written as:
(Carbon Dioxide + Water + Sunlight → Glucose + Oxygen)
Photosynthesis Process
Raw Materials Needed for Photosynthesis
| Raw Material | Source |
|---|---|
| Carbon Dioxide (CO₂) | Absorbed from air through tiny pores called stomata |
| Water (H₂O) | Absorbed from soil through roots |
| Sunlight | Captured by chlorophyll in the leaves |
| Chlorophyll | Green pigment present in chloroplasts of leaf cells |
Products of Photosynthesis
- Glucose (C₆H₁₂O₆): Used by the plant as food/energy, and stored as starch.
- Oxygen (O₂): Released into the air through stomata, which is essential for the respiration of most living organisms, including humans.
Factors Affecting the Rate of Photosynthesis
- Light Intensity: More light generally increases the rate, up to a certain limit.
- Carbon Dioxide Concentration: Higher CO₂ levels can increase the rate, up to a certain limit.
- Temperature: Photosynthesis works best within a moderate temperature range; too high or too low slows it down.
- Water Availability: Insufficient water reduces the plant's ability to photosynthesize.
Why This Topic Matters
Photosynthesis is the basis of the food chain, since almost all life depends directly or indirectly on the food and oxygen produced by plants. It also connects to topics like respiration, the carbon cycle, and plant structure, making it one of the most important and frequently repeated Biology topics in TLT, ECT, PST, and JEST exams.
Practice MCQs
1. What is the green pigment responsible for absorbing sunlight in photosynthesis?
a) Hemoglobin b) Chlorophyll c) Melanin d) Carotene
2. Which gas is released as a byproduct of photosynthesis?
a) Carbon Dioxide b) Nitrogen c) Oxygen d) Hydrogen
3. Where does photosynthesis mainly take place in a plant cell?
a) Nucleus b) Mitochondria c) Chloroplast d) Cell wall
4. Which raw material for photosynthesis is absorbed by the roots?
a) Oxygen b) Water c) Carbon Dioxide d) Glucose
5. What is the main food product formed during photosynthesis?
a) Starch only b) Protein c) Glucose d) Fat
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