Unlabeled Diagram of Ribosome – Blank Sheet to Label

All 12 parts on the diagram

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Start here: 5 main parts 5

Large subunit The larger of the ribosome's two parts. It joins the amino acids into a chain.
Small subunit The smaller of the two parts. It holds the mRNA and reads its code.
mRNA Messenger RNA, the copy of a gene that the ribosome reads.
tRNA Transfer RNA, which brings the amino acid that matches each mRNA codon.
Polypeptide chain The chain of amino acids the ribosome is building. It will fold into a protein.

What it is made of: 2 2

Ribosomal RNA Ribosomal RNA, the RNA each subunit is built around. It does the actual chemistry of joining amino acids.
Ribosomal proteins The many proteins built into each subunit alongside the rRNA.

In the cell: 5 5

Nucleolus The region inside the nucleus where the rRNA is made. The subunits are put together here.
Free ribosomes Ribosomes floating in the cytoplasm. The proteins they make stay in the cell.
Bound ribosomes Ribosomes on the rough endoplasmic reticulum.
Rough ER Folded membranes, rough-looking because of the ribosomes on them. In full, the rough endoplasmic reticulum.
Polysome Several ribosomes moving along one mRNA at once. Each makes its own copy of the protein.

How this list was compiled: Read 2026-09-27. Wikipedia, Ribosome, https://en.wikipedia.org/wiki/Ribosome : the ribosome decodes codons in an mRNA and, with tRNA, joins amino acids into a polypeptide chain; a ribosome has a small and a large subunit, each of one or more ribosomal RNA molecules and many ribosomal proteins; ribosomes are free, floating in the cytoplasm (their proteins released into the cytosol), or membrane-bound, attached to the rough endoplasmic reticulum; a polysome of two or more ribosomes can move along one mRNA at a time; in eukaryotes they are assembled partly in the nucleolus. Licence: own work

The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

How it works

This unlabeled diagram of a ribosome is two drawings. Above, one ribosome cut open while it builds a protein. Below, a cell with its ribosomes drawn as dots. Twelve label lines want a name, seven above and five below.

Read the full guide

The twelve names for the blank ribosome structure

Seven go on the ribosome: large subunit, small subunit, ribosomal RNA, ribosomal proteins, mRNA, tRNA and polypeptide chain. Five go on the cell: nucleolus, free ribosomes, bound ribosomes, rough ER and polysome.

Which shape takes which name

The dome is the large subunit and the bowl under it the small one. The looping strands inside are ribosomal RNA, and the pale discs ribosomal proteins. The flat strip between the subunits is mRNA, the T standing on it tRNA, and the string of beads leaving the top the polypeptide chain. In the cell, the oval inside the nucleus is the nucleolus. Loose dots are free ribosomes, dots on the wavy bands bound ribosomes, the bands rough ER, and dots strung on one thread a polysome.

The bead on top of the T is an amino acid, and the circle round the nucleolus is the nucleus. Neither takes a name.
Strands and discs lie in both subunits. Each has one line, and both lines end in the large subunit.
A sheet that asks for the 60S and the 40S subunit means the large and the small one of a eukaryotic cell.

Questions and answers

Is a ribosome an organelle?

It is sometimes called one. The word organelle is often kept for parts of a cell that have a membrane, and a ribosome has none, so it may be described as a non-membranous organelle.

Do prokaryotic cells have ribosomes?

Yes. Ribosomes are found in all cells. A prokaryote has 70S ribosomes, with a 50S and a 30S subunit. The ribosomes in the cytosol of a eukaryotic cell are 80S, with a 60S and a 40S subunit.

Why do a 50S and a 30S subunit make a 70S ribosome?

Because S, the Svedberg unit, measures how fast a particle settles in a centrifuge and not its size. The figures of the two subunits therefore do not add up.

What does a ribosome look like under a microscope?

A dense granule: that is how ribosomes were first seen, in the mid-1950s, with an electron microscope. A bacterial ribosome is about 20 nanometers across and a eukaryotic one 25 to 30.