Chloroplast Labeled Diagram – 10 Parts, Envelope to Granum

All 10 parts on the diagram

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Envelope (double membrane) The chloroplast's covering of two membranes, an outer and an inner one. A narrow space lies between them.
Stroma The fluid that fills the chloroplast round the thylakoids. Sugars are made here in the second stage of photosynthesis.
Thylakoid A flat, disc-shaped sac of membrane. The light-catching stage of photosynthesis happens in its membrane.
Thylakoid lumen The space enclosed by a thylakoid's membrane.
Granum A stack of thylakoids, like a pile of coins. The plural is grana.
Stroma lamellae Flat, unstacked thylakoids that join one granum to the next.
Starch granule Grains of starch, the store for the sugar the chloroplast makes.
Plastoglobuli Small droplets of fat and protein floating in the stroma. They are attached to the thylakoids.
Chloroplast DNA The chloroplast's own DNA, separate from the DNA in the cell's nucleus.
Ribosomes The chloroplast's own ribosomes, which make some of its proteins.

How this list was compiled: Read 2026-09-27. (1) Wikipedia, Chloroplast, https://en.wikipedia.org/wiki/Chloroplast : the envelope of an outer and an inner membrane; the stroma, in which float nucleoids of chloroplast DNA, chloroplast ribosomes, the thylakoid system with plastoglobuli, and starch granules; thylakoids arranged in grana stacks joined by stromal thylakoids (lamellae); chloroplasts contain their own DNA separate from the nucleus. (2) OpenStax Biology 2e, 8.1 Overview of Photosynthesis, https://openstax.org/books/biology-2e/pages/8-1-overview-of-photosynthesis (used to check the names only, nothing copied): a double membrane envelope of an outer and an inner membrane; stacked, disc-shaped thylakoids; a stack of thylakoids called a granum; the stroma round them; the thylakoid lumen inside the thylakoid membrane. 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 chloroplast labeled diagram: the organelle where plants make food by photosynthesis, cut open and stood upright to show its membranes, its stacks of thylakoids and what floats in the stroma.

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Membranes and stacks

The envelope is two membranes round the outside. Inside, flat thylakoids are stacked into grana, with the lumen inside each thylakoid, and stroma lamellae join one granum to the next. The light-catching stage of photosynthesis happens in the thylakoid membranes.

In the stroma

The stroma fills the rest of the chloroplast; sugars are made here. Starch granules store them, and plastoglobuli, the chloroplast's own DNA and its ribosomes float in the stroma too.

Stroma and stoma are different words: the stroma is inside a chloroplast; a stoma is a pore in a leaf.

Questions and answers

What is the difference between a thylakoid and a granum?

A thylakoid is one flat, disc-shaped sac of membrane. A granum is a stack of thylakoids; the plural is grana.

Where does photosynthesis happen in a chloroplast?

The light-dependent stage happens in the thylakoid membranes, and the sugar-making stage in the stroma round them.

Why does a chloroplast have its own DNA?

Chloroplasts are thought to come from free-living cyanobacteria taken in by an ancient cell, so they still carry some of their own DNA and ribosomes.