Defence Against Disease Practice Questions

Name two physical barriers that prevent pathogens entering the human body.

The stomach produces hydrochloric acid.

Explain how hydrochloric acid helps to protect the body from disease.

Tears contain an enzyme called lysozyme.

Describe how lysozyme defends the eye against infection.

Explain how the waxy cuticle of a leaf helps to defend the plant against pathogens.

Plant cells have a cell wall made of cellulose. Explain how the cell wall acts as a defence even when a pathogen has entered the leaf.

Some plants produce chemicals that defend them against pests and pathogens. A few of these chemicals are used in human medicine.

Give one example of a plant chemical used as a human medicine and state what it is used for.

Explain why the skin usually prevents pathogens from entering the body.

The bacteria have antigens on their surface.

Explain how the student's specific immune system responds to these bacteria.

The antibodies made against these bacteria give the student no protection against a different species of bacteria.

Explain why.

Using Figure 1, describe two differences between the response after the second injection and the response after the first injection.

Explain why the response after the second injection is different from the response after the first injection.

The vaccine contains an inactive form of the pathogen. Explain why an inactive form is used rather than a living, active pathogen.

The lining of the trachea and bronchi contains goblet cells that make mucus and ciliated epithelial cells.

Explain how these two types of cell work together to protect the lungs from infection.

Some plants produce chemicals that kill or deter pests and pathogens.

Describe how these chemical defences work, and explain why some of these chemicals are useful to humans.

Give one other visible symptom, apart from spots on leaves, that could suggest a plant has a disease.

Before deciding that the rose bushes have a disease caused by a pathogen, the grower should eliminate possible environmental causes.

Give two environmental causes that could produce similar symptoms in the rose bushes.

The grower records which bushes in her rose bed are affected. All the affected bushes are in one corner of the bed, next to a hedge, and the rest of the bed is healthy.

Explain what this distribution suggests about the cause of the symptoms.

Describe one laboratory method the grower could use to confirm which pathogen is infecting the rose bushes.

Calculate the percentage decrease in the number of reported cases between 2000 and 2010.

Give your answer to 3 significant figures.

Explain the change in the number of reported cases between 2015 and 2020, using the idea of herd immunity.

Give one disadvantage of immunisation programmes.

Predict the shape of the anti-X antibody response after the injection on day 30 compared with the injection on day 0.

After the injection of protein Y on day 60, the concentration of anti-X antibody did not increase.

Explain why.

The response to protein Y on day 60 was slow and produced only a small amount of anti-Y antibody, even though the mouse's immune system was already active.

Explain why the response to Y was a primary response.

The plant clinic uses a test kit containing antibodies to identify the pathogen.

Explain how antibodies can be used to identify which pathogen is present.

The plant clinic also carries out DNA analysis on the leaf sample. Suggest one advantage of DNA analysis over identifying the disease from visible symptoms alone.

The gardener notices that only the plants along one wall of the greenhouse, where a watering pipe leaks, are affected.

Suggest two things the gardener should do next to find out whether the symptoms are caused by a pathogen or by the growing conditions.

Explain how vaccinating a high proportion of the population protects babies who cannot be vaccinated.

Some parents choose not to have their children vaccinated.

Evaluate the decision not to vaccinate a healthy child against this disease.