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Photosynthesis: an overview

Summary

Photosynthesis is how plants, algae and cyanobacteria capture the energy in sunlight and store it in sugars. They take in carbon dioxide and water and release oxygen. In plants it takes place in chloroplasts, mostly in the leaf's mesophyll cells, and gases pass in and out through pores called stomata. Almost every other organism depends on the sugars it makes.

Draft. License: CC BY 4.0 (this summary). Sources: [S1] OpenStax (Rice University), "Biology, 8.1 Overview of Photosynthesis" (CC BY 4.0).

Facts

• id: F1 claim: Photosynthesis is the only biological process that captures energy from sunlight and converts it into chemical compounds (carbohydrates) that organisms use for metabolism. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F2 claim: Only plants, algae and cyanobacteria perform photosynthesis; they are photoautotrophs, while animals, fungi and most other bacteria are heterotrophs. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F3 claim: Chemoautotrophs are bacteria that make sugars using energy from inorganic chemical compounds rather than sunlight. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F4 claim: The substrates are sunlight, carbon dioxide and water; the products are oxygen and the three-carbon sugar glyceraldehyde-3-phosphate (GA3P), which can be converted into glucose, sucrose and other sugars. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F5 claim: The overall equation is 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2. confidence: high date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F6 claim: In plants, photosynthesis mainly occurs in the mesophyll, the middle cell layer of leaves; CO2 and O2 move through stomata, whose opening is controlled by guard cells. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F7 claim: In autotrophic eukaryotes it occurs in chloroplasts; chlorophyll sits in the membranes of stacked thylakoids. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F8 claim: The textbook states that photosynthesis powers 99 percent of Earth's ecosystems, and that fossil fuels hold solar energy stored by ancient photosynthesis. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02

Caveats

• Introductory level; the light-dependent reactions and Calvin cycle are covered in later sections (8.2, 8.3).
• The newer Biology 2e edition carries a different (non-commercial) license; this note uses the CC BY 4.0 first edition.

Pointers

• id: P1 answers: Full details and updates where: https://openstax.org/books/biology/pages/8-1-overview-of-photosynthesis access: free, public web page

@misc{iil_note_bx9bj5gt,
  author = {{iinventedlight Library}},
  title = {{Photosynthesis: an overview}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-02},
  url = {https://iinventedlight.com/library/reference/us-gov/photosynthesis-overview/},
  note = {Permanent ID iil:note:bx9bj5gt. License: CC-BY-4.0. Summary of https://openstax.org/books/biology/pages/8-1-overview-of-photosynthesis.},
}

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