Question 1: Define bacteria and describe their basic structure.

Answer: Bacteria are single-celled microorganisms with a simple cell structure, including a cell wall, plasma membrane, cytoplasm, and genetic material, often lacking a nucleus.

Question 2: Explain the process of binary fission in bacterial reproduction.

Answer: Binary fission is a form of asexual reproduction where a bacterial cell divides into two identical daughter cells after replicating its genetic material.

Question 3: Calculate the number of bacteria after 4 hours, if a single bacterium divides every 30 minutes. Show your working. (Initial count = 1 bacteria)

Answer: Number of divisions = 4 hours / 0.5 hours = 8 divisions; total bacteria = 2^8 = 256.

Question 4: If a bacterial culture starts with 100 bacteria and doubles every 20 minutes, how many bacteria will there be after 2 hours? Show your working.

Answer: Number of doubling periods = 2 hours / 0.33 hours ≈ 6; total bacteria = 100 × 2^6 = 100 × 64 = 6400.

Question 5: Identify two factors that affect the rate of bacterial growth in a culture.

Answer: Temperature and nutrient availability.

Question 6: What safety precautions should be taken when handling bacterial cultures in a laboratory setting?

Answer: Wearing gloves and lab coats, sterilising equipment, working in a sterile environment, and proper disposal of cultures.

Question 7: A bacterial population grows from 50 to 800 in 3 hours. Assuming exponential growth, estimate the doubling time.

Answer: Using doubling formula: 50 × 2^n = 800; 2^n = 16; n = 4; total time = 3 hours; doubling time = 3 hours / 4 = 0.75 hours or 45 minutes.

Question 8: Describe an experiment to determine the effect of temperature on bacterial growth.

Answer: Set up identical bacterial cultures in nutrient broth and incubate them at different temperatures (e.g., 10°C, 25°C, 37°C, 50°C). Measure bacterial growth by optical density or colony count after a fixed period. Record and compare the growth rates to determine the optimal temperature for bacterial reproduction.

Question 9: In an industrial setting, how can knowledge of bacterial growth be utilised to improve fermentation processes?

Answer: By controlling temperature, pH, and nutrient supply to optimise bacterial growth rates, thus increasing efficiency and yield of fermentation products such as antibiotics, enzymes, or food products.

Question 10: Explain why bacteria are considered both beneficial and harmful to humans.

Answer: Beneficial bacteria are involved in processes like digestion, production of antibiotics, and environmental nutrient cycling. Harmful bacteria can cause diseases such as tuberculosis, food poisoning, and infections, posing health risks.