Photosynthesis

noun (uncountable)

/ˌfəʊtəʊˈsɪnθɪsɪs/

Photosynthesis is the biological process by which photoautotrophic organisms — primarily plants, algae, and cyanobacteria — convert light energy (solar radiation) into chemical energy stored in glucose, using carbon dioxide and water as reactants and releasing oxygen as a by-product: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. The process occurs in two stages: the light-dependent reactions (in thylakoid membranes) and the Calvin cycle (in the stroma of chloroplasts). Photosynthesis is the primary entry point of energy into virtually all food chains on Earth and is central to understanding carbon sequestration — a key dimension of India's Nationally Determined Contribution (NDC) under the Paris Agreement, which commits to creating an additional carbon sink of 2.5–3 billion tonnes of CO₂ equivalent through forest cover by 2030.

✍️ Usage in a UPSC answer

India's NDC commitment to sequester an additional 2.5–3 billion tonnes of CO₂ equivalent by 2030 is operationally contingent on expanding forest cover — the ecosystem-scale expression of photosynthesis — across degraded lands targeted by the Green India Mission.

Synonyms

carbon fixation (partial)photoautotrophic carbon assimilationsolar energy conversion

Antonyms

cellular respirationchemosynthesis (alternative energy source)oxidative decomposition

🌱 Word Family

photosynthesise/photosynthesize (verb), photosynthetic (adjective), photosynthetically (adverb), photoautotroph (noun)

🔡 Root

Greek phōs/phōtos = light + synthesis = putting together (from syn- = together + tithenai = to place)

📜 Etymology

The word was constructed from Greek phōs (genitive phōtos, light) and synthesis (a putting together, from syntithenai = to put together). It was first used in its modern scientific sense by German botanist Wilhelm Pfeffer in the late 19th century, though the process was systematically studied from the 18th century (van Helmont, Priestley, Ingenhousz). The combining form photo- (from Greek phōs) is widely productive in scientific vocabulary: photograph, photon, photosensitive.

🧠 Memory Hook

Photosynthesis = photo (light) + synthesis (put together) — plants use light to PUT TOGETHER glucose from CO₂ and water. Think of a solar panel factory: photo = solar energy input, synthesis = manufacturing output. Plants are biological solar factories.

⚗️ General Science 📖 Seen in: Human Body Systems — Organ Systems, Ph... 📋 Also in Key Terms

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