Concept:The rough appearance of Rough Endoplasmic Reticulum (RER) under a microscope is due to the presence of ribosomes attached to its outer surface.
Explanation:Ribosomes are small organelles composed of rRNA and proteins.
They exist in two forms: free ribosomes in the cytoplasm and bound ribosomes attached to the RER.
Bound ribosomes translate mRNA into polypeptide chains, giving the RER its characteristic rough texture.
The RER is mainly involved in the synthesis, modification, and folding of proteins destined for secretion, membrane incorporation, or lysosomes.
Proteins are modified within the RER lumen and then transported to the Golgi apparatus for further processing.
Other organelles do not contribute to the rough appearance:
Centrosome organizes microtubules during cell division.
Lysosome contains digestive enzymes for waste breakdown.
Peroxisome breaks down fatty acids and detoxifies harmful substances.
The ribosomes attached to the RER are 80S in eukaryotes, and their discovery by George Palade won the Nobel Prize in 1974.
Thus, the only particle responsible for the rough look is the ribosome.
Answer:Ribosome (Option B).