AQA GCSE Combined Science: Biology: Infection and Response

When a person is infected by a pathogen for the first time, it can take several days before they recover. After vaccination against the same pathogen, the person usually does not become ill at all if they later meet it.

Explain how vaccination protects a person against a disease. In your answer you should refer to the role of white blood cells and antibodies. (6 marks)

A new drug to lower blood pressure was tested in a clinical trial. Patients were split into two groups: one group received the new drug and the other received a placebo (a pill containing no drug). The mean fall in blood pressure was recorded.

Group	Number of patients	Mean fall in blood pressure / mmHg
New drug	500	18
Placebo	500	4

(a) Calculate how many times greater the mean fall in blood pressure was for the new-drug group compared with the placebo group. Show your working. (2 marks)

(b) Explain why a placebo group was included in this trial. (2 marks)

Pathogens can be bacteria, viruses, fungi or protists.

(a) Name the type of pathogen that causes measles, and state one way measles is spread. (2 marks)

(b) Malaria is caused by a protist. Name the organism that acts as a vector, spreading the malarial protist from person to person. (1 mark)

Antibiotics, such as penicillin, have greatly reduced deaths from bacterial diseases.

(a) Explain why a doctor would not prescribe an antibiotic to treat a patient who has a viral disease such as influenza (flu). (2 marks)

(b) Give one reason why doctors are worried about the rise of antibiotic-resistant strains of bacteria. (1 mark)

The skin is part of the body's non-specific first line of defence against pathogens.

State two ways the human body defends itself against pathogens entering through the breathing system (airways). (2 marks)

Painkillers such as paracetamol are often given to people who are ill.

State what painkillers do for a patient who has an infectious disease. (1 mark)