To which structure inside a bacterium does tetracycline bind?

It binds to the 30S subunit of the bacterial 70S ribosome.

Explain how tetracycline brings protein synthesis to a halt.

By occupying the site on the small ribosomal subunit where the next transfer RNA must dock, it prevents the arrival of any further amino acid, so the growing polypeptide chain cannot be extended.

Describe the cell wall of a Gram positive bacterium.

A Gram positive bacterium has a single very thick layer of peptidoglycan, strengthened by teichoic acids and lying exposed at the outer surface of the cell.

Eduqas A-Level Biology A400QS

Biological Molecules

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Immunology and Disease: Antibiotics

Tetracycline and the Gram negative barrier

3 things to know
Component 3

Overview

How tetracycline brings protein synthesis to a halt, cell wall of a Gram positive bacterium and cell wall of a Gram negative bacterium.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why is tetracycline bacteriostatic rather than bactericidal?

Key term

Why does tetracycline not stop protein synthesis in the cytoplasm of a human cell?

Key term

Suggest why a long course of tetracycline can still cause side effects in human tissues.

Questions from this subtopic

Each one with the model answer underneath.

1
To which structure inside a bacterium does tetracycline bind?
Model answer
It binds to the 30S subunit of the bacterial 70S ribosome.
2
Explain how tetracycline brings protein synthesis to a halt.
Model answer
By occupying the site on the small ribosomal subunit where the next transfer RNA must dock, it prevents the arrival of any further amino acid, so the growing polypeptide chain cannot be extended.
3
Why is tetracycline bacteriostatic rather than bactericidal?
Model answer
The proteins already made continue to work and the cell stays alive, but with no new protein it cannot grow or divide, so the population is held steady rather than destroyed.
4
Why does tetracycline not stop protein synthesis in the cytoplasm of a human cell?
Model answer
Cytoplasmic ribosomes in a human cell are 80S and are built from subunits of a different size and shape, so tetracycline does not bind to them.
5
Suggest why a long course of tetracycline can still cause side effects in human tissues.
Model answer
Mitochondria contain their own 70S ribosomes, which resemble the bacterial ones closely enough for the drug to interfere with them if it accumulates.
6
Describe the cell wall of a Gram positive bacterium.
Model answer
A Gram positive bacterium has a single very thick layer of peptidoglycan, strengthened by teichoic acids and lying exposed at the outer surface of the cell.

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