Final answer:
The smooth endoplasmic reticulum (smooth ER) is not involved in protein synthesis, as it's responsible for lipid synthesis, carbohydrate metabolism, and detoxification, whereas the rough ER, ribosomes, Golgi complex, and nucleus all play roles in protein synthesis.
Step-by-step explanation:
The component not involved in protein synthesis is D) smooth ER:
In the context of protein synthesis, the smooth endoplasmic reticulum (smooth ER) is not directly involved. The smooth ER is primarily responsible for the synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions. During protein synthesis, ribosomes are the molecular machines that use mRNA as a template to assemble proteins from amino acids.
The rough ER is studded with ribosomes and is involved in the synthesis of proteins that are destined to be exported from the cell or inserted into the cell membrane. The Golgi complex is involved in the modification, sorting, and packaging of proteins for secretion. Finally, the nucleus is where mRNA is transcribed from DNA before it goes to the ribosomes for translation into protein.