Eukaryotic Cells

There are large non-membranous RNA protein complexes which are necessary for protein synthesis. There are dense granules of to $200\,?? diameter (as revealed by electron microscope) and found either in free state or attached to the outside of cytoplasmic membrane just like that of ER or nuclear membrane, etc through ribophorins.

Pits are formed on the cell wall is due to lack of secondary wall material. Pits appear circular, oval or angular in surface view and are of two types-simple and bordered. The simple pits are the areas with only primary wall without any secondary thickening and have uniform with of the pit chamber or cavity. The bordered pits are, however, more complicated as the secondary wall partially outgrows the pit to form a dome-shaped structure with a tiny perforation in the middle.

Lysosomes are also known as suicide bags. They are small vesicles that contain a mixture of powerful lytic enzymes. It is important that the membrane of lysosomes remains intact because if the enzymes leak out they could destroy the whole cell.