Which organisms have 70S ribosomes?

Which organisms have 70S ribosomes?

• A. Eukaryotes
• B. Prokaryotes
• C. Both
• D. Neither

Answer: (B)

Ribosome sedimentation rate distinguishes prokaryotes from eukaryotes in how they make proteins. Prokaryotes have 70S ribosomes, made of a 50S large subunit and a 30S small subunit. In contrast, eukaryotes have 80S ribosomes in the cytosol and on the rough endoplasmic reticulum, built from a 60S large subunit and a 40S small subunit. Because of this, the organisms with 70S ribosomes are prokaryotes. (Note: mitochondria and chloroplasts in eukaryotes also contain 70S ribosomes due to their bacterial origin, but the general distinction for whole organisms remains: prokaryotes have 70S.) This difference also explains why many antibiotics target bacterial 70S ribosomes without affecting human 80S ribosomes.

Ribosome sedimentation rate distinguishes prokaryotes from eukaryotes in how they make proteins. Prokaryotes have 70S ribosomes, made of a 50S large subunit and a 30S small subunit. In contrast, eukaryotes have 80S ribosomes in the cytosol and on the rough endoplasmic reticulum, built from a 60S large subunit and a 40S small subunit. Because of this, the organisms with 70S ribosomes are prokaryotes. (Note: mitochondria and chloroplasts in eukaryotes also contain 70S ribosomes due to their bacterial origin, but the general distinction for whole organisms remains: prokaryotes have 70S.) This difference also explains why many antibiotics target bacterial 70S ribosomes without affecting human 80S ribosomes.