Photosynthesis happens in the chloroplasts of plant and algal cells, mainly in the leaf cells’ mesophyll layer. Inside each chloroplast, it specifically takes place in the thylakoid membranes (light reactions) and the stroma (Calvin cycle).

Quick Scoop

  • In eukaryotic cells, photosynthesis takes place in chloroplasts, organelles that contain the green pigment chlorophyll.
  • The light-dependent reactions happen in the thylakoid membranes, where chlorophyll absorbs light and converts it to chemical energy (ATP and NADPH).
  • The light-independent reactions (Calvin cycle, often called “dark reactions”) occur in the stroma, the fluid-filled space around the thylakoids, where CO₂ is used to build sugars.
  • In a whole plant, most chloroplasts are in mesophyll cells in the leaves, so that is where most photosynthesis occurs.

Tiny story version

Imagine a plant cell as a city and the chloroplasts as little solar factories. These factories pack stacks of “solar panels” (thylakoids) where light is captured, and a “workshop floor” (stroma) where that energy is used to assemble sugar molecules from carbon dioxide and water.

TL;DR: When someone asks “where does photosynthesis happen in the cell,” the precise answer is: in the chloroplasts—on the thylakoid membranes for light reactions and in the stroma for the Calvin cycle.

Information gathered from public forums or data available on the internet and portrayed here.