In this video, we're going to introduce ribosomes. Ribosomes are sometimes referred to as nonmembranous organelles, meaning they are not made up of membranes. This is important to keep in mind because most of the organelles we will discuss moving forward are made up of membranes, but ribosomes are not. It's crucial to remember that ribosomes are nonmembranous organelles, as both textbooks and professors often refer to them simply as organelles.

Now, we have mentioned this term "ribosomes" a few times in our previous lesson videos, but what exactly are these ribosomes, and what do they do for a cell? Well, you can think of ribosomes as tiny molecular machines inside of cells that build proteins. Ribosomes are found in all living cells, regardless of whether those cells are prokaryotic or eukaryotic, or whether they are animal or plant cells. The process conducted by ribosomes that builds proteins is specifically named "translation."

Translation is the scientific term for the process conducted by ribosomes to build proteins. Later in our course, we will discuss this process in much more detail. For now, you should know that ribosomes build proteins by conducting this process called translation. It's also important to note that ribosomes can either be free ribosomes, which are free-floating in the cytoplasm, or attached ribosomes, which are not free and instead are attached to another organelle inside the cell, such as the rough endoplasmic reticulum (ER). We will talk more about the endoplasmic reticulum later in our course. But for now, let's take a look at this image we have here to better understand ribosomes.

Notice in the representation of a eukaryotic animal cell, these little tiny blue circles scattered throughout are ribosomes. If we zoom into one of these ribosomes, you will notice that some of them are free ribosomes, meaning they are just free-floating in the cytoplasm of the cell. The cytoplasm is the space inside the cell, in between organelles, and inside the cell membrane. However, whether they are free or attached ribosomes, their main function is to build proteins. This little blue ribosome we are zooming into is building a chain of amino acids which represents the protein being built.

Some of the ribosomes are attached ribosomes and are attached to another organelle such as the rough ER. If we zoom into this image, you'll see that the rough ER is this blue structure surrounding the nucleus. Attached to the rough ER are these tiny little blue dots, which are ribosomes specifically attached ribosomes. Free ribosomes make proteins that end up floating in the cytoplasm, but when the attached ribosomes make proteins, those proteins end up on the inside of the rough ER.

This concludes our introduction to ribosomes as machines that build proteins. We will apply some of these concepts moving forward in our course. I'll see you all in our next video.