Ribosomes, endoplasmic reticulum, & Golgi Apparatus

Ribosomes:

Ribosomes are small, dark staining granules composed of proteins and a variety of RNA called ribosomal RNA. Ribosomes are sites of protein synthesis.

Endoplasmic Reticulum:

The ER is an extensive system of interconnected tubes and parallel membranes enclosing fluid filled cavities(cisternae)that coils and twists through the cytosol. The two varieties of the ER are the rough ER and smooth ER. The ROUGH ER is studded with ribosomes. It's ribosomes manufacture all proteins secreted from cells, integral proteins and phospholipids that form part of all cellular membranes are manufacture there, and the enzymes needed to catalyze lipid synthesis have their active sites in the external face if the ER, where the needed substrates are readily available. The smooth ER is a continuation of the rough ER and consists of tubules arranged in a looping network. It's enzymes do not play a role in protein synthesis; instead, they catalyze reactions involved in multiple processes.

Golgi Apparatus:

It consists of stacked and flattened membranous sacs,associated with swarms of tiny membranous vesicles. It's major function is to modify, concentrate, and package the proteins and lipids made at the rough ER. The transport vesicles that bud off from the rough ER move to and fuse with the receiving side of the Golgi apparatus.