SunlightThe energy that drives photosynthesis. Chlorophyll in the chloroplasts absorbs the light, and it powers the light-dependent reactions.
WaterTaken up by roots and carried up the stem to the leaves. In the chloroplast the light-dependent reactions split it, which gives off oxygen.
Carbon dioxideA gas from the air. It enters the leaf through tiny pores called stomata. In the chloroplast the Calvin cycle builds it into sugar.
OxygenGiven off when water is split in the light-dependent reactions. It leaves the leaf through the stomata.
GlucoseThe sugar the plant makes. It holds the energy taken from the light. The plant uses it to live and grow, or stores it as starch.
LeafThe main place photosynthesis happens. Its cells are packed with chloroplasts.
Inside the chloroplast: 10 5
ChloroplastThe part of a plant cell where photosynthesis happens. Both stages take place inside it.
Light-dependent reactionsThe first stage, on the thylakoid membranes. Light energy splits water, giving off oxygen, and charges up ATP and NADPH.
Calvin cycleThe second stage, in the stroma. It spends ATP and NADPH to build carbon dioxide into sugar. It is also called the light-independent reactions.
ATP and NADPHThe energy carriers made by the light-dependent reactions. The Calvin cycle spends them.
ADP and NADP+The spent carriers, handed back to be charged again. They go from the Calvin cycle to the light-dependent reactions.
How this list was compiled: Read 2026-09-27. (1) Wikipedia, Photosynthesis, https://en.wikipedia.org/wiki/Photosynthesis : light-dependent reactions split water, giving off oxygen, and make NADPH and ATP; the light-independent reactions, the Calvin cycle, build carbon dioxide into sugars using that ATP and NADPH; sugars such as glucose, stored as starch; plants close their stomata to save water; the chloroplast's thylakoid membranes and stroma. (2) OpenStax Biology 2e, 8.1 Overview of Photosynthesis, https://openstax.org/books/biology-2e/pages/8-1-overview-of-photosynthesis (used to check, nothing copied): carbon dioxide and water in, sugar and oxygen out; the leaf and its stomata; the two stages in the chloroplast, with ATP and NADPH going to the Calvin cycle and ADP and NADP+ coming back. Licence: own work
The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work
How it works
A photosynthesis diagram labeled twice: a plant with what goes in and out, then a chloroplast with the two stages. Start with the plant's 6 parts; the arrows light up in both views.
Read the full guide
On the plant
Light reaches the leaf, water comes up from the roots, and carbon dioxide enters from the air. The leaf gives off oxygen and makes glucose, a sugar the plant uses to live and grow.
In the chloroplast
The light-dependent reactions on the stacked thylakoids use light to split water, giving off oxygen and charging ATP and NADPH. The Calvin cycle in the stroma spends them to build carbon dioxide into sugar, and hands ADP and NADP+ back.
Match the arrows: every arrow into or out of the plant has a twin on the chloroplast, so the two views tell one story.
Questions and answers
What is the equation for photosynthesis?
Six carbon dioxide plus six water, with light, make one glucose plus six oxygen: 6CO2 + 6H2O → C6H12O6 + 6O2.
What are the two stages of photosynthesis?
The light-dependent reactions, on the thylakoid membranes, and the Calvin cycle, also called the light-independent reactions, in the stroma. The first makes ATP and NADPH; the second spends them to make sugar.
Where does the oxygen come from?
From water. The light-dependent reactions split water molecules, and the oxygen is given off as a by-product through the leaf's stomata.