Which organelle is responsible for protein synthesis in a cell?

Ribosomes are the organelles primarily responsible for protein synthesis within a cell. They can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum, forming what is known as the rough ER. During protein synthesis, ribosomes translate messenger RNA (mRNA) sequences into polypeptide chains, which then fold into functional proteins. This process is crucial for cell function and overall organism health, as proteins play essential roles in nearly all biological processes.

The other organelles mentioned have distinct and important roles. Lysosomes are involved in digestion and waste removal within the cell, the Golgi apparatus is responsible for modifying, sorting, and packaging proteins for secretion or delivery to other organelles, and mitochondria are known as the powerhouses of the cell, providing energy through ATP production. However, none of these organelles are directly involved in the synthesis of proteins, which is why ribosomes are the correct choice for this question.