What biomolecules would notably be synthesized in the rough endoplasmic reticulum?

The rough endoplasmic reticulum (RER) is primarily involved in the synthesis of proteins. This organelle is studded with ribosomes on its cytoplasmic surface, which gives it the "rough" appearance. These ribosomes are the sites where mRNA is translated into polypeptide chains, which are then threaded into the lumen of the RER. Within this lumen, proteins can undergo proper folding and post-translational modifications, such as glycosylation.

The proteins synthesized in the RER include those destined for secretion, incorporation into the cell membrane, or for use in lysosomes. This process is crucial for the production of various types of proteins, including enzymes, hormones, and antibodies, all fundamental for cellular functions and overall health.

In contrast, carbohydrates, fatty acids, and nucleotides are not synthesized in the RER. Carbohydrate metabolism mainly occurs in the cytoplasm and the Golgi apparatus, while fatty acid synthesis typically takes place in the cytoplasm and mitochondria. Nucleotides are synthesized in the cell's nucleoplasm and cytoplasm. This specialization of function illustrates the diverse capabilities of eukaryotic cells and the importance of compartmentalization in cellular processes.