Previous Year Questions (2016-19) - Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. It is a vital process for the existence of life on Earth as it provides oxygen and a source of energy-rich organic molecules.

Importance of Photosynthesis
- Oxygen Production: Photosynthesis is responsible for approximately half of the oxygen production on Earth, which is essential for the survival of aerobic organisms.
- Food Production: The glucose produced during photosynthesis serves as the primary source of energy for plants and is also a fundamental component of the food chain.
- Carbon Dioxide Regulation: Photosynthesis helps in regulating the levels of carbon dioxide in the atmosphere, mitigating the effects of global warming.

Process of Photosynthesis
1. Light Reactions:
- Light Absorption: Chlorophyll pigments in the chloroplasts absorb light energy from the sun.
- Electron Transfer: The absorbed energy is used to excite electrons in the chlorophyll molecules, which are then transferred to electron carriers.
- ATP Production: The excited electrons are passed along a series of electron carriers, generating ATP (adenosine triphosphate), a high-energy molecule.
- Oxygen Release: Water molecules are split into oxygen, hydrogen ions, and electrons. The released oxygen is a byproduct of photosynthesis.

2. Calvin Cycle (Dark Reactions):
- Carbon Fixation: Carbon dioxide from the atmosphere is incorporated into organic molecules, primarily through the enzyme RuBisCO.
- Sugar Synthesis: The fixed carbon dioxide is converted into glucose and other sugars using ATP and NADPH (Nicotinamide adenine dinucleotide phosphate) produced in the light reactions.
- Regeneration: Some molecules produced during the Calvin cycle are used to regenerate the initial molecule required for carbon fixation.

Mock Test Questions
1. What is the primary product of photosynthesis?
2. Which pigment is responsible for absorbing light energy in photosynthesis?
3. What are the two main stages of photosynthesis?
4. Name the enzyme involved in carbon fixation during the Calvin cycle.
5. How does photosynthesis contribute to oxygen production on Earth?

Remember to always refer to reliable sources and practice a wide range of questions to enhance your understanding of photosynthesis. Good luck with your preparation!

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