The cytosol is basically the cytoplasm minus all the structures and organelles. So if we take out all the organelles between the cell membrane and the nucleus, we are simply left with the fluid region. And the fluid is known as the cytosol. And the cytosol contains these free ribosomes that basically move about this entire fluid region. Now let's move on to the mitochondria. The mitochondria is a very important structure in the eukaryotic cell.