A toxin, usually a protein, secreted by living bacterial cells.

What is an endotoxin?

A lipopolysaccharide in the cell wall of some bacteria, released when the cell dies and breaks down.

When is endotoxin released?

When the bacterial cell dies and breaks open (lyses).

Why can an exotoxin cause symptoms far from the infection?

It is secreted and carried in the blood to other tissues.

What does M. tuberculosis do to the lungs?

It invades and multiplies in lung tissue, destroying it and forming tubercles and cavities.

Give two symptoms of TB.

Persistent cough, blood in sputum, weight loss or night sweats.

Why can killing Salmonella briefly increase endotoxin?

The dead cells break open and release the endotoxin from their cell walls.

An organism that causes disease.

Bacteria as pathogensEdexcel A-Level Biology B: Flashcards

Card 1 of 120 of 12 known

Question

Name the two main ways bacteria cause harm to a host.

Tap or press Space to reveal

Tap card or press Space to flip

See all 12 cards

Name the two main ways bacteria cause harm to a host.: By invading and destroying host tissue, and by producing toxins.
What is an exotoxin?: A toxin, usually a protein, secreted by living bacterial cells.
What is an endotoxin?: A lipopolysaccharide in the cell wall of some bacteria, released when the cell dies and breaks down.
Which bacterium is the exotoxin example in the specification?: Staphylococcus (S. aureus).
Which bacterium is the endotoxin example?: Salmonella.
Which bacterium is the example of invasion of host tissue?: Mycobacterium tuberculosis.
When is endotoxin released?: When the bacterial cell dies and breaks open (lyses).
Why can an exotoxin cause symptoms far from the infection?: It is secreted and carried in the blood to other tissues.
What does M. tuberculosis do to the lungs?: It invades and multiplies in lung tissue, destroying it and forming tubercles and cavities.
Give two symptoms of TB.: Persistent cough, blood in sputum, weight loss or night sweats.
Why can killing Salmonella briefly increase endotoxin?: The dead cells break open and release the endotoxin from their cell walls.
What is a pathogen?: An organism that causes disease.

Exam questions on Bacteria as pathogens

A patient develops a red, swollen surgical wound. Swabs taken from the wound grow Staphylococcus aureus, and the bacteria are found only in the wound. Over the next day the patient develops a high fever, a rash and a fall in blood pressure. Blood tests find a toxin made by S. aureus circulating in the blood, but no bacterial cells.
The bacteria were found only in the wound. Explain why the patient has symptoms in tissues far from the wound.2 marks
Several students became ill 12 hours after a barbecue, with fever, vomiting and diarrhoea. Salmonella was cultured from undercooked chicken that they had eaten. A doctor explained that part of their symptoms was caused by a component of the Salmonella cell wall that is released when the bacteria die and break open.
A student suggests that killing large numbers of Salmonella in the gut could briefly make the symptoms worse. Explain why this is plausible.2 marks
A 34-year-old man has had a cough for eight weeks, with blood in his sputum, night sweats and weight loss. A chest scan shows several small rounded lesions in his lungs and areas where lung tissue has been destroyed, leaving cavities. Mycobacterium tuberculosis is cultured from his sputum. Unlike Staphylococcus aureus, M. tuberculosis does not make a powerful toxin.
Explain how M. tuberculosis causes the lung damage seen in this patient.3 marks

See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).