3.5 Helicobacter, Ebola and the virus life cycle
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Name the pathogen that causes stomach ulcers, and give the type of pathogen it is.
Mark scheme
- Helicobacter (pylori) (1)
- bacterium (1)
Model answer
Stomach ulcers are caused by Helicobacter pylori, which is a bacterium.
Ebola is spread through body fluids.
Suggest two ways health workers can reduce its spread during an outbreak.
Mark scheme
Any two from:
- isolate patients (1)
- wear protective clothing / gloves / masks (1)
- safe burial of the dead (1)
- trace contacts (1)
- vaccination (1)
Model answer
Isolate the patients, and wear full protective clothing when caring for them.
Describe the lytic pathway of a virus.
Mark scheme
- virus attaches to the host cell (1)
- injects its genetic material / DNA / RNA (1)
- host cell makes new viral genetic material and proteins / new viruses assembled (1)
- cell bursts / lyses, releasing the new viruses (1)
Model answer
The virus attaches to a host cell and injects its genetic material. The cell uses it to make new viral genetic material and proteins, which are assembled into new viruses. The cell then bursts, releasing the viruses to infect other cells.
Give two differences between the lytic and lysogenic pathways.
Mark scheme
Any two from:
- lysogenic: viral DNA inserted into host DNA; lytic: not inserted (1)
- lytic: new viruses made straight away; lysogenic: dormant / no new viruses at first (1)
- lytic: cell bursts; lysogenic: cell not destroyed / divides normally (1)
Model answer
In the lysogenic pathway the viral DNA is inserted into the host DNA, and no new viruses are made at first. In the lytic pathway new viruses are made straight away and the cell bursts.
In the lysogenic pathway, the virus causes no symptoms for a long time.
Explain why.
Mark scheme
- viral DNA is dormant / inserted in host DNA (1)
- no new viruses made / cells not destroyed (until it enters the lytic pathway) (1)
Model answer
The viral DNA sits inside the host DNA and is just copied when the cell divides. No new viruses are made and no cells are destroyed until a trigger switches it to the lytic pathway.
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