Ribosomes are a type of organelle that is found in all cell types, including both plant-like and animal-like cells, and they have one of the most important jobs.

Ribosomes are very small molecules whose function is to assist the cell in making proteins. Even under a microscope, ribosomes appear as tiny dots, floating around a cell as well as some that are attached to organelles.

In almost every place that you look in a cell, you will find ribosomes. In plant and animal cells they are attached to the organelles of the nucleus and the endoplasmic reticulum.

Even in bacteria cells you can look in the cytoplasm and see them free floating.

The origins of the ribosomes can be found in a part of the cell nucleus called the nucleolus. Ribosomes are made rRNA, a specific material that contains two parts called the “small subunit” and the “large subunit,” and each plays a role in making proteins.

Both of these subunits are made of RNA and come together when the ribosome is ready to create new proteins.


The large subunit is the location where the new protein bonds are made. In prokaryotic cells its called “50S” and in eukaryotic cells it’s called “60S.”

The small subunit is really just slightly smaller than the large subunit. Its job is to control the information flow during protein synthesis. In prokaryotic cells it’s called “50S” and in eukaryotic cells it’s called “40S.”

The “S” in the names of the subunits is for the Svedberg Unit which is a unit of measure.

The Protein Synthesis process of Ribosomes

Protein manufacturing in a cell is critical for its survival. Ribosomes work with a variety of other cell parts, including the nucleus, to make proteins.

They use a complicated process called “translation” for protein making, and this involves creating the protein with amino acids.

Amino acids have been compared to “small building blocks” and the ribosomes put these building blocks in the correct order so that the finished products are proteins.

Ribosomes have the ability to read and then translate the instructions so that the put the amino acid building blocks together correctly to make the mRNA protein. mRNA proteins are called the “messenger” proteins that carry the coding sequences to the cells.

Explaining Translation

There are different steps that ribosomes take in the “translation” process so that they can make proteins.  If you know anything about computer programming, you will see that we use the same kind of file “start and stop” coding that the ribosomes use.

  • The messenger RNA join together with the two subunits.
  • The ribosome locates the “codon” on the RNA which is the starting point.
  • Moving down the RNA, the ribosome reads the instructions for which amino acids to attach to the proteins, noting that a new amino acid is represented on the RNA with every 3 letters.
  • The ribosome builds up the protein by attaching amino acids.
  • When it perceives the RNA “stop code”, it stops building the protein and it sends a message that the protein is finished and ready.

Fun Ribosome Facts

  • The number of ribosomes in each cell is astounding. One of your cells contains about 10 million ribosomes.
  • Most cell organelles are surrounded by a membrane to protect it. Ribsomes are different because they are an organelle, but don’t have a protective membrane.
  • 3 Scientists discovered the ribosome in 1974 and won a Nobel Prize for the discovery: Christian de Duve, Albert Claude, and George Emil Palada.
  • Ribosomes are made in the nucleus in an area called the nucleolus. When they are completed they are ejected out of the nucleus through the membrane’s small pores.
  • Many scientific words are created based on their meaning or purpose. The “rib” portion of the word ribosome is from the RNA (ribonucleic acid) that gives the protein making instructions.
  • Ribosomes are found in both free float as well as clinging to some of the organelles.

Interesting Facts about Biology

  • The intestines is the largest internal organ in the human body.
  • Some plants use chemicals to defend themselves against other plants trying to take over their territory.
  • More men are color blind than women. Only 1% of women are color blind, but nearing 8% of men are color blind.
  • Fern leaves are called “fronds.”
  • Humans have a blind spot in our eyes at the location where the retina and optical nerve connects.
  • The image that our retina sees is really upside down. Our brain changes it so that it is right side up.

Ribosomes Quiz

Now let's test what you have learned!