BRAINCAKE70S Ribosomes
Ribosomes are the sites of protein synthesis (translation). They are made of ribosomal RNA (rRNA) and protein, and each ribosome has two subunits, one large and one small. Ribosomes are not surrounded by a membrane.
Prokaryotic cells have 70S ribosomes, made of a large 50S subunit and a small 30S subunit. The ribosomes in the cytoplasm of eukaryotic cells are larger, 80S, made of 60S and 40S subunits. In bacteria the ribosomes are free in the cytoplasm, because there is no endoplasmic reticulum.
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Key terms in this lesson
- endosymbiotic theory
- The theory that mitochondria and chloroplasts evolved from free-living prokaryotes engulfed by, and made mutually dependent with, an early eukaryotic cell.
More in Prokaryotic Cells
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- Cell Surface Membrane
- Plasmids
- Nucleoid
- Gram-Staining
- Antibiotics
- Alternative Classification of Bacteria
- Viruses
All 31 lessons in Prokaryotic Cells · All Edexcel AS-level Biology topics