What causes rough endoplasmic reticulum to look "rough" under a microscope?

Question

Madeline Andrews · Accepted Answer

The ribosomes on the surface.

The rough endoplasmic reticulum (ER) is called 'rough' because it has organelles called ribosomes attached to the surface.

Ribosomes are the organelles that turn mRNA into proteins. These proteins are initially long strings of amino acids. This string has to be folded in the right way to form a functional protein. The rough ER helps with the folding of these amino acid-strings and at the same time prevents their degradation by enzymes in the cell.

Because of this cooperation, the ribosomes can be attached to the ER. The ribosomes can then synthesize the amino acid string straight into the ER, making the process safer and more efficient.

Gabriella Anderson · Answer

undefined The rough appearance of the endoplasmic reticulum (ER) under a microscope is due to the presence of ribosomes attached to its surface. These ribosomes are responsible for protein synthesis within the cell. The rough endoplasmic reticulum (RER) plays a crucial role in the synthesis, folding, and modification of proteins that are destined for secretion or insertion into cellular membranes. The ribosomes attached to the RER provide a site for protein synthesis, and as the newly synthesized proteins are produced, they pass into the lumen of the RER for further processing. The abundance of ribosomes on the surface of the RER gives it a rough or granular appearance when viewed under a microscope, distinguishing it from the smooth endoplasmic reticulum (SER), which lacks ribosomes and appears smooth.