Level of life
Cell
The smallest unit that can live on its own. Every living thing is made of one or more cells.
Chloroplasts
Capture light energy to make sugar by photosynthesis.Source: OpenStax, 2018Source: Archibald, 2015Source: Bar-On & Milo, 2019
Step 2 of 7ReadingStructure
Inside the cell: chloroplasts
Chloroplasts are where plants make their own food. They capture energy from sunlight and use it to turn carbon dioxide and water into sugar, releasing oxygen.
Inside chloroplasts, stacks of thylakoid membranes hold chlorophyll that absorbs light. The light reactions make ATP and NADPH and split water, releasing oxygen. The Calvin cycle in the surrounding stroma uses them to fix carbon dioxide into sugar.
Like mitochondria, chloroplasts have their own DNA and descend from an endosymbiotic bacterium, in this case a cyanobacterium. The enzyme rubisco fixes CO₂ in the stroma; a 2019 estimate put rubisco's total mass on Earth at about 0.7 gigatonnes, most of it in land plant leaves.
- Structure
Double outer membrane, internal thylakoid membranes stacked into grana, and fluid stroma containing DNA and ribosomes.
- Key molecules
- Chlorophyll
- Rubisco
- ATP synthase
- NADPH
- Chloroplast DNA
How Chloroplasts connects
Chloroplasts is part of
Chloroplasts is the site of
Process
Photosynthesis
Using light energy to turn carbon dioxide and water into sugar, releasing oxygen.
Chloroplasts evolved from
Organism or group
Bacteria
Small single-celled organisms without a nucleus, found almost everywhere on Earth. Most bacteria in the human body are harmless, and some are helpful.
Chloroplasts is described by
Idea or model
Endosymbiosis
Mitochondria and chloroplasts descend from bacteria that came to live inside other cells long ago.
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Sources & further reading
The explanations on this page are our own summaries of these sources. Follow a link to read the original; if anything here disagrees with it, the original wins. How we choose and check sources.
Biology 2e (opens the original in a new tab)
OpenStax (2018). OpenStax, Rice University.
Free introductory college textbook.
TextbookEducationalLicence: CC BY-NC-SA 4.0 (linked, not reused)
Endosymbiosis and eukaryotic cell evolution (opens the original in a new tab)
Archibald JM (2015). Current Biology 25:R911-R921.
Peer-reviewedReviewThe global mass and average rate of rubisco (opens the original in a new tab)
Bar-On YM, Milo R (2019). Proceedings of the National Academy of Sciences 116:4738-4743.
Estimates about 0.7 gigatonnes of rubisco on Earth, mostly in land plant leaves.
Peer-reviewedPrimary researchThe path of carbon in photosynthesis (opens the original in a new tab)
Bassham JA, Benson AA, Calvin M (1950). Journal of Biological Chemistry 185:781-787.
Historical paperPrimary research