What cell organelle is responsible for protein synthesis?

Ribosomes are the cell organelles specifically responsible for protein synthesis. They are made up of ribosomal RNA and proteins and can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum, forming what is known as rough ER. During protein synthesis, ribosomes read the sequence of messenger RNA (mRNA) and translate it into a specific amino acid sequence to form proteins. This process is essential for cell function and growth, as proteins play numerous roles within the cell, including acting as enzymes, structural components, and signaling molecules.

The nucleus, while crucial for storing and transmitting genetic information, is not directly involved in the assembly of proteins, rather it facilitates the expression of genes which eventually leads to protein synthesis. Mitochondria are primarily known for energy production through ATP synthesis, and chloroplasts are involved in photosynthesis in plant cells, neither of which is related to the direct synthesis of proteins.