Final answer:
A cell with numerous ribosomes is primarily engaged in the synthesis of proteins, as ribosomes are the cellular structures that translate mRNA to build proteins.
Step-by-step explanation:
If a cell had many ribosomes, it is likely busy making proteins. Ribosomes are essential cellular structures that are involved in the process called protein synthesis. They translate the genetic instructions from messenger RNA (mRNA) into amino acid sequences to build proteins. Ribosomes consist of two subunits, each comprising proteins and ribosomal RNA (rRNA), which function together to form polypeptides that eventually become proteins.
Ribosomes can either be found floating freely in the cytoplasm or attached to the cytoplasmic side of the endoplasmic reticulum (ER). This formation is known as the rough endoplasmic reticulum (RER) due to the ribosomes' dot-like appearance. While ribosomes themselves are involved in protein synthesis, the smooth endoplasmic reticulum (SER) is associated with lipid production, but without the presence of ribosomes. Accordingly, a high number of ribosomes in a cell suggests that the cell is extensively engaged in synthesizing proteins.