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General Science

Photosynthesis

Biological process to convert light into chemical energy

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Overview

Photosynthesis is a system of biological processes by which photopigment-bearing autotrophic organisms, such as most plants, algae and cyanobacteria, convert light energy—typically from sunlight—into the chemical energy necessary to fuel their metabolism. The term photosynthesis usually refers to oxygenic photosynthesis, a process that releases oxygen as a byproduct of water splitting. Photosynthetic organisms store the converted chemical energy within the bonds of intracellular organic compounds, typically carbohydrates like sugars, starches, phytoglycogen and cellulose. When needing to use this stored energy, an organism's cells then metabolize the organic compounds through cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth.

Source: Wikipedia — Photosynthesis (CC BY-SA)

Key concepts

How Photosynthesis connects to the ideas, people and events around it.

  1. Chlorophyll

    uses

    Chlorophyll is the green pigment found in the chloroplasts of photosynthetic organisms. It absorbs light most efficiently in the blue and red wavelengths, driving the light-dependent reactions.

  2. Thylakoid

    occurs in

    The thylakoid membrane is a lipid bilayer inside chloroplasts that houses the photosystems and electron transport chain. Its stacked structures, called grana, are the site of the light-dependent reactions.

  3. Photosystem

    includes

    Light-dependent reactions capture photons to split water and generate ATP and NADPH. These reactions take place within the thylakoid membranes of chloroplasts.

  4. Calvin cycle

    includes

    The Calvin cycle, also known as the carbon fixation pathway, uses ATP and NADPH to convert carbon dioxide into glucose. It occurs in the stroma of chloroplasts after the light-dependent reactions.

  5. Oxygen

    produces

    Oxygen is released as a byproduct when water molecules are split during the light-dependent reactions. The accumulation of atmospheric oxygen enabled the evolution of aerobic life.

  6. Jan Ingenhousz

    studied by

    Jan Ingenhousz was an 18th‑century Dutch physician who demonstrated that plants produce oxygen only in the presence of light. His experiments confirmed the role of sunlight in photosynthesis.

  7. Biological carbon fixation

    involves

    Carbon fixation is the process of converting inorganic carbon dioxide into organic compounds. In photosynthesis, this step is carried out by the Calvin cycle.

  8. Viridiplantae

    performed by

    Green plants are the primary organisms that perform oxygenic photosynthesis on Earth. Their chloroplasts contain chlorophyll and the necessary machinery for converting light into chemical energy.

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Questions about Photosynthesis

What is Photosynthesis?

Photosynthesis is a system of biological processes by which photopigment-bearing autotrophic organisms, such as most plants, algae and cyanobacteria, convert light energy—typically from sunlight—into the chemical energy necessary to fuel their metabolism. The term photosynthesis usually refers to oxygenic photosynthesis, a process that releases oxygen as a byproduct of water splitting.

What are the key concepts related to Photosynthesis?

The main concepts connected to Photosynthesis include Chlorophyll, Thylakoid, Photosystem, Calvin cycle, Oxygen, Jan Ingenhousz, Biological carbon fixation, Viridiplantae. Each is linked on the map above with its own summary.

Which exams cover Photosynthesis?

Photosynthesis is part of General Science, which appears in the syllabus of UPSC CAPF, NDA, CDS, AFCAT, SSC CGL, SSC CHSL and 18 more exams.