Which organelle is primarily responsible for synthesizing proteins and repairing the plasma membrane?

The rough endoplasmic reticulum (Rough ER) is primarily responsible for synthesizing proteins. It is characterized by the presence of ribosomes on its cytoplasmic surface, which gives it a "rough" appearance under a microscope. These ribosomes play a crucial role in translating messenger RNA into polypeptide chains, effectively synthesizing proteins.

In addition to protein synthesis, the rough ER is also involved in the processing and modification of these proteins, preparing them for their specific functions within the cell or for secretion outside the cell. Additionally, the rough ER contributes to the repair and maintenance of the plasma membrane by synthesizing membrane proteins and ensuring the proper incorporation of these proteins into the membrane structure.

The role of the rough ER in protein synthesis connects seamlessly to its function in maintaining and repairing the plasma membrane, as many proteins are integral to the membrane's structure and functionality.

Other organelles like lysosomes, peroxisomes, and centrioles have specialized functions that do not directly involve the synthesis of proteins or the direct repair of the plasma membrane. Lysosomes are primarily involved in digestion and waste processing; peroxisomes focus on oxidation reactions and detoxification; and centrioles play a key role in cell division rather than protein synthesis