Question 1: Define the term 'antigen' and explain its role in the immune response.

Answer: An antigen is a substance, often a protein on the surface of a pathogen, that triggers an immune response by stimulating the production of antibodies.

Question 2: Describe the process by which a white blood cell recognises and responds to a pathogen.

Answer: White blood cells recognise antigens on pathogens through specific receptors. They then activate mechanisms such as phagocytosis or stimulating antibody production to neutralise or destroy the pathogen.

Question 3: What is the primary function of memory cells in the immune system?

Answer: Memory cells recognise pathogens more quickly upon re-infection, enabling a faster and stronger immune response during subsequent exposures.

Question 4: Calculate the amount of antibody produced if a single B cell produces 10,000 antibodies per hour over a 24-hour period.

Answer: Answer: 240,000 antibodies. (Calculation: 10,000 antibodies/hour × 24 hours = 240,000 antibodies)

Question 5: Propose a simple experimental method to test the effectiveness of a vaccine in preventing infection.

Answer: A possible method involves dividing a suitable sample of volunteers into two groups: one receiving the vaccine and the other receiving a placebo. Both groups are then exposed to the pathogen under controlled conditions. The effectiveness is assessed by comparing the infection rates between the two groups, ensuring safety protocols are followed throughout.

Question 6: Identify the variable that is being tested in the experiment described above.

Answer: The variable being tested is the presence or absence of the vaccine.

Question 7: Explain why it is important to include a control group in vaccine effectiveness experiments.

Answer: A control group is essential to compare outcomes and determine whether the vaccine has a real effect in preventing infection, ruling out other factors or placebo effects.

Question 8: Describe one safety precaution that must be considered when conducting experiments involving pathogens.

Answer: Safety precautions include working in a sterile environment, using protective clothing, and following proper disposal procedures for infectious materials.

Question 9: Describe how herd immunity can protect a population from infectious diseases.

Answer: Herd immunity occurs when a high proportion of the population is immune to a disease, reducing its spread and providing protection to individuals who cannot be vaccinated.

Question 10: Explain why antibiotics are ineffective against viruses and how this influences treatment options.

Answer: Antibiotics target specific bacterial structures or functions, which viruses lack. Since viruses do not have cell walls or metabolic pathways that antibiotics affect, these drugs are ineffective. Therefore, antiviral drugs or vaccines are used to treat viral infections.