LIFE SCIENCE

Detailed explanation-1: -Proteins are assembled at organelles called ribosomes. When proteins are destined to be part of the cell membrane or exported from the cell, the ribosomes assembling them attach to the endoplasmic reticulum, giving it a rough appearance.

Detailed explanation-2: -The answer is the presence of ribosomes on the surface. The rough endoplasmic reticulum contains ribosomes on the surface whereas the smooth endoplasmic reticulum does not. Ribosomes are another type of organelle that are made of ribosomal RNA and protein. Their main function in the cell is to produce protein.

Detailed explanation-3: -Rough ER contains two integral membrane proteins, ribophorins I and II, that have molecular masses of 65 kDa and 63 kDa, respectively. These proteins remain attached to ribosomes when the ER membrane is dissolved with detergent and they can be crosslinked to ribosomes by chemical reagents.