Ribosomes
Ribosomes are vital cellular structures responsible for protein synthesis, observed first by George Palade in 1953. They consist of ribonucleic acid (RNA) and proteins and lack a surrounding membrane. In eukaryotic cells, ribosomes are classified as 80S ribosomes, while in prokaryotic cells, they are referred to as 70S ribosomes. Each ribosome comprises two subunits - a larger subunit and a smaller subunit.
Key Points:
- Eukaryotic Ribosomes: Composed of 60S and 40S subunits, totaling 80S.
- Prokaryotic Ribosomes: Composed of 50S and 30S subunits, totaling 70S.
- The sedimentation coefficient (S) indicates the density and size of the ribosomal units.
- Ribosomes are essential for translating mRNA into proteins, contributing to various cellular functions.
- They can exist freely in the cytoplasm or be associated with the rough endoplasmic reticulum (ER).
Understanding ribosomes is crucial as they serve as the site of protein synthesis, which is essential for cellular activities and function.