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

Answer: An antigen is a substance that triggers an immune response, typically a protein on the surface of pathogens, which stimulates the production of specific antibodies.

Question 2: Describe the main difference between non-specific and specific immune responses.

Answer: Non-specific responses are immediate and protect against all pathogens without recognition, whereas specific responses target particular pathogens through immune memory and antibody production.

Question 3: Explain how phagocytes contribute to defending the body against infection.

Answer: Phagocytes engulf and digest pathogens through phagocytosis, helping to remove invaders and present antigens to activate other immune cells.

Question 4: Fill in the blank: During the immune response, lymphocytes produce __________ that specifically target the pathogen's antigens.

Answer: antibodies

Question 5: Multiple choice: Which of the following is a feature of the secondary immune response? A) It occurs immediately after the first exposure to a pathogen. B) It involves the production of memory cells. C) It takes several weeks to develop. D) It does not produce antibodies.

Answer: B

Question 6: Calculate the number of antibodies produced if each plasma cell produces 10,000 antibodies per hour over a period of 24 hours, assuming 100 plasma cells are active. Show your working and give your answer in scientific notation.

Answer: 2.4 x 10^9

Question 7: Design a simple experiment to test the effectiveness of a vaccine in providing immunity against a specific pathogen. Describe the variables involved and safety precautions.

Answer: Students could vaccinate one group with the vaccine and keep a control group unvaccinated. Both groups are then exposed to the pathogen in a controlled environment. Variables include the vaccination status (independent variable) and infection rate (dependent variable). Safety precautions include using non-pathogenic strains or simulated exposure, wearing protective equipment, and ensuring ethical approval.

Question 8: Describe how memory cells contribute to long-term immunity after infection or vaccination.

Answer: Memory cells remain in the body after an infection or vaccination, enabling the immune system to respond rapidly and effectively if the same pathogen is encountered again.

Question 9: Explain the importance of herd immunity in controlling infectious diseases.

Answer: Herd immunity occurs when a large proportion of the population is immune, reducing the spread of disease and protecting those who are not immune.

Question 10: Identify two factors that can influence the success of vaccination programmes in a population.

Answer: Public acceptance and access to vaccines.

Question 11: Discuss how new technologies, such as mRNA vaccines, have improved the fight against infectious diseases.

Answer: mRNA vaccines allow rapid development and design of vaccines by instructing cells to produce specific pathogen proteins, leading to a strong immune response. They can be quickly adapted to emerging strains and have shown high efficacy, as seen in recent COVID-19 vaccines.