Final answer:
The rough endoplasmic reticulum (RER) contains ribosomes, which are responsible for protein synthesis and assembly. The RER looks 'rough' due to these ribosomes and is also involved in phospholipid production for cell membranes.
Step-by-step explanation:
The section of the endoplasmic reticulum that contains ribosomes is the rough endoplasmic reticulum (RER). The RER is so named because its membrane is dotted with ribosomes, which are the organelles responsible for protein synthesis. The ribosomes on the RER translate proteins directly into the lumen, where they undergo modifications such as folding and the addition of sugars.
Ribosomes are composed of two ribosomal RNA subunits and their primary function is to synthesize proteins by wrapping around mRNA to start the translation process. The newly synthesized proteins are transported into the rough ER and may eventually be sent to the Golgi apparatus. Furthermore, the RER is also involved in the production of phospholipids for cell membranes.