Describe photosynthesis as the process by which plants synthesise carbohydrates from raw materials using energy from light

Sourav PanNovember 14, 2024

Answered step-by-step

Photosynthesis is a vital biological process through which plants, algae, and some bacteria synthesize carbohydrates from raw materials, utilizing energy derived from sunlight. This process is essential for life on Earth, as it not only provides food for the plants themselves but also produces oxygen and serves as the foundation of the food chain for other organisms.

Overview of Photosynthesis

1. Raw Materials:
   • Carbon Dioxide (CO₂): Plants absorb carbon dioxide from the atmosphere through small openings in their leaves called stomata.
   • Water (H₂O): Water is taken up by plant roots from the soil and transported to the leaves through specialized vascular tissues known as xylem.
2. Energy Source:
   • Light Energy: The energy required for photosynthesis is derived from sunlight. Chlorophyll, the green pigment found in chloroplasts of plant cells, captures this light energy.

The Process of Photosynthesis

Photosynthesis can be summarized in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).

1. Light-Dependent Reactions

• Location: These reactions occur in the thylakoid membranes of chloroplasts.
• Process:
  • When chlorophyll absorbs light energy, it excites electrons, leading to a series of reactions that produce energy-rich molecules.
  • Water molecules are split (photolysis) to release oxygen gas (O₂) as a byproduct.
  • The energy captured is stored in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are used in the next stage of photosynthesis.

2. Light-Independent Reactions (Calvin Cycle)

• Location: These reactions take place in the stroma of chloroplasts.
• Process:
  • ATP and NADPH generated during the light-dependent reactions are utilized to convert carbon dioxide into glucose through a series of enzymatic reactions.
  • The Calvin cycle involves three main steps: carbon fixation, reduction phase, and regeneration of ribulose bisphosphate (RuBP).
  • Ultimately, glucose (C₆H₁₂O₆) is produced, which can be used by the plant for energy or converted into other carbohydrates like starch for storage.