Ribosome

Definition

Ribosomes are molecular machines within cells that facilitate the translation of mRNA into proteins. They consist of rRNA and proteins, forming two subunits that join during protein synthesis.

5 Must Know Facts For Your Next Test

1. Ribosomes can be found in both prokaryotic and eukaryotic cells, though they differ slightly in size and composition.
2. They have two subunits: a larger one and a smaller one, which come together during translation.
3. Ribosomes read mRNA sequences and translate them into polypeptide chains by linking amino acids in the order specified by the mRNA.
4. In prokaryotes, ribosomes are 70S (composed of 50S and 30S subunits), while in eukaryotes, they are 80S (composed of 60S and 40S subunits).
5. Ribosomes can be free-floating in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER.

Review Questions

• What are the main components of ribosomes?
• How do ribosomal subunits differ between prokaryotic and eukaryotic cells?
• What is the primary function of ribosomes during protein synthesis?

Related terms

mRNA:

Messenger RNA that carries genetic information from DNA to ribosomes for protein synthesis.

tRNA:

Transfer RNA that brings amino acids to ribosomes during translation.

Polypeptide Chain: A sequence of amino acids linked together by peptide bonds, formed as a result of translation at the ribosome.