Which cellular structure makes proteins for the cell?

Which cellular structure makes proteins for the cell?

• A. Ribosomes
• B. Mitochondria
• C. Nucleolus
• D. Chloroplasts

Answer: (A)

Proteins are built at ribosomes, the cellular machines that translate genetic instructions into amino acid chains. Messenger RNA carries the code from DNA to the ribosome, and transfer RNA brings the correct amino acids to match each codon. The ribosome links these amino acids together, forming a polypeptide that then folds into a functional protein. Some ribosomes float freely in the cytoplasm to make cytosolic proteins, while others are bound to the rough endoplasmic reticulum to produce proteins destined for secretion or membranes. Mitochondria are mainly energy producers and have their own ribosomes for a small subset of proteins, but they aren’t the primary site of general protein synthesis. The nucleolus is where ribosomal RNA is made and ribosome subunits are assembled, not where proteins are actively synthesized. Chloroplasts perform photosynthesis and also contain ribosomes, but their role is specialized to plant cells. Thus, ribosomes are the main site of protein production in the cell.

Proteins are built at ribosomes, the cellular machines that translate genetic instructions into amino acid chains. Messenger RNA carries the code from DNA to the ribosome, and transfer RNA brings the correct amino acids to match each codon. The ribosome links these amino acids together, forming a polypeptide that then folds into a functional protein. Some ribosomes float freely in the cytoplasm to make cytosolic proteins, while others are bound to the rough endoplasmic reticulum to produce proteins destined for secretion or membranes.

Mitochondria are mainly energy producers and have their own ribosomes for a small subset of proteins, but they aren’t the primary site of general protein synthesis. The nucleolus is where ribosomal RNA is made and ribosome subunits are assembled, not where proteins are actively synthesized. Chloroplasts perform photosynthesis and also contain ribosomes, but their role is specialized to plant cells. Thus, ribosomes are the main site of protein production in the cell.