Final answer:
S cells are coated with a polysaccharide capsule giving them a smooth appearance and pathogenic qualities, while R cells lack this capsule and appear rough, making them non-pathogenic. These terms should not be confused with smooth and rough ER or smooth muscle cells.
Step-by-step explanation:
The difference between Smooth (S) type cells and R type cells specifically refers to strains of bacteria, such as pneumococcus (S. pneumoniae), where S type cells are coated with a polysaccharide (mucus) capsule that makes them appear smooth on petri dishes, and R type cells lack this capsule, resulting in a rough appearance. The presence of this capsule in S cells enables them to evade immune responses, making them pathogenic, while R cells are non-pathogenic. These cells should not be confused with the smooth and rough endoplasmic reticulum found inside eukaryotic cells, or with smooth muscle cells, which are types of cells or organelles found in higher organisms that serve different functions.