Answer
The Rough Endoplasmic Reticulum is associated with translation of proteins. It is rough because it has ribosomes in it, which makes it easy to remember the protein function.
The Smooth Endoplasmic Reticulum is associated with the production and metabolism of fats/lipids. The SER does not have ribosomes in it, therefore it is smooth.
Work Step by Step
Page 100-101: Endoplasmic Reticulum Headline; Figure 3.28