Small bumps located on portions of the endoplasmic reticulum are called

Ribosomes

Explanation:

Small bumps on endoplasmic reticulum are the ribosomes which give a rough appearance to the endoplasmic reticulum and therefore called Rough endoplasmic reticulum. These ribosomes on RER are required for protein synthesis. Protein is synthesised on ribosomes by translation and transported by endoplasmic reticulum to the cell