Question 1: Define a virus and explain how it differs from bacteria.

Answer: A virus is a tiny infectious agent that requires a host cell to reproduce, unlike bacteria which can grow and reproduce independently.

Question 2: Describe the basic structure of a virus, including its main components.

Answer: A virus generally consists of genetic material (DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an outer lipid envelope.

Question 3: Explain how viruses infect host cells and reproduce.

Answer: Viruses attach to specific receptors on a host cell, inject their genetic material, and hijack the cell's machinery to produce new virus particles, which then infect other cells.

Question 4: What is the role of the lipid envelope in some viruses?

Answer: The lipid envelope helps the virus enter host cells more easily and can help it evade the host's immune system.

Question 5: Describe a method used by scientists to prevent the spread of viruses.

Answer: Practicing good hygiene, such as hand washing, vaccination, and using protective barriers like masks, helps prevent virus spread.

Question 1: If a virus population doubles every 30 minutes, how many viruses will there be after 3 hours if starting with 1,000 viruses? (Use the formula: N = N0 * 2^(t / d), where N0 = initial number, t = time in minutes, d = doubling time in minutes.)

Answer: N = 1000 * 2^(180 / 30) = 1000 * 2^6 = 1000 * 64 = 64,000 viruses

Question 2: A vaccine is 95% effective. If 200 people are vaccinated, how many are expected to be protected against the virus?

Answer: Number protected = 200 * 0.95 = 190 people

Question 1: Design a simple experiment to test the effectiveness of handwashing in removing viruses from the skin. Include variables and safety precautions.

Answer: Students can contaminate their hands with a safe, non-pathogenic virus or fluorescent dye, then wash hands using different methods (e.g., soap and water, sanitizer). Variables include type of handwashing method (independent) and the amount of virus remaining (dependent). Safety precautions include wearing gloves, avoiding ingestion or contact with harmful substances, and sanitizing all materials afterward.

Question 2: Identify three variables that should be controlled in an experiment testing the effect of a new antiviral drug.

Answer: Variables to control include the virus strain used, the dosage of the drug, and the duration of exposure.

Question 1: A study shows that after administering a vaccine, the number of infected individuals decreases from 150 to 30 over a month. Describe what this data suggests about the vaccine's effectiveness.

Answer: The significant reduction in infection numbers suggests that the vaccine is highly effective in preventing the virus infection among the population studied.

Question 1: Explain the process by which a virus can cause disease in a human host, including the steps from entry to symptom development. (6 marks)

Answer: Viruses infect humans by attaching to specific receptors on host cells, injecting their genetic material, and hijacking the cell's machinery to produce new viruses. The replication process damages or destroys host cells, leading to symptoms such as fever and fatigue. The immune response to viral invasion also contributes to symptoms.

Question 1: Describe how mRNA vaccines, like those used for COVID-19, work to protect individuals from viral infection.

Answer: mRNA vaccines deliver genetic instructions to cells to produce a viral protein, which triggers an immune response. This prepares the immune system to recognize and fight the actual virus if exposed.

Question 2: Discuss the importance of vaccination programs in controlling viral outbreaks in communities.

Answer: Vaccination programs help develop herd immunity, reducing the spread of viruses. They protect vulnerable populations and prevent outbreaks, saving lives and reducing healthcare costs.