--- title: "Light-Dependent Reactions in the Thylakoid Membrane" description: "Thylakoid membranes hold the pigments that trap light, and the trapped energy splits water, reduces NADP and makes ATP. Those two products are the input to the reactions that fix carbon." canonical: https://lightmysky.com/learn/science/light-dependent-reactions-in-the-thylakoid-membrane-mt_3Ooq3BfmpX source: https://lightmysky.com/learn/science/light-dependent-reactions-in-the-thylakoid-membrane-mt_3Ooq3BfmpX.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Light-Dependent Reactions in the Thylakoid Membrane Thylakoid membranes hold the pigments that trap light, and the trapped energy splits water, reduces NADP and makes ATP. Those two products are the input to the reactions that fix carbon. Subject: Science · Area: Organisms & Life Processes · Ages 16 to 17 Page: https://lightmysky.com/learn/science/light-dependent-reactions-in-the-thylakoid-membrane-mt_3Ooq3BfmpX ## Ready when they can - Places the light-dependent reactions in the thylakoid membrane and says why they happen there. - Names what water is split into and where each product goes. - Lists the two products that carry energy and reducing power onward. ## Lesson: Catching light in the thylakoid The light-dependent reactions run in the thylakoid membranes of the chloroplast. Chlorophyll in the photosystems traps photons there, which is exactly why this stage needs membranes packed with pigment. Its whole job is to stock two carriers, ATP and reduced NADP, that the next stage spends to build sugar. With no light the stocks drain, so sugar making stalls. Trapped light energy splits water into oxygen, protons and electrons. Oxygen drifts away as a byproduct of the split. The protons pile up inside the thylakoid space while the electrons travel down a transport chain. **Example.** The chain spends its energy in two ways. It pumps yet more protons across the membrane, and ATP synthase lets them flow back to build ATP. At the end of the line, NADP picks up electrons and hydrogen to become reduced NADP. Picture two batteries charged for later: ATP and reduced NADP. **Tip.** Sugar itself is built in the stroma, not here. If a question asks where carbon is fixed, leave the thylakoid and head for the stroma. **Recap.** In the thylakoid membrane, light splits water and charges ATP and reduced NADP for the next stage. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Photosynthesis and Limiting Factors](https://lightmysky.com/learn/science/photosynthesis-and-limiting-factors-mt_PDn831oIih) ## Opens up - [The Calvin Cycle and Carbon Fixation](https://lightmysky.com/learn/science/the-calvin-cycle-and-carbon-fixation-mt_zGOCx9mNrx)