Microbiology and Disease — Biology Unit 10 practice.
This unit covers bacteria and viruses, immune response and infectious diseases — essential concepts for Biology. Use our interactive study games to test your understanding, or review questions in traditional format below.
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This unit covers bacteria and viruses, immune response and infectious diseases — essential concepts for Biology. Use our interactive study games to test your understanding, or review questions in traditional format below.
Key Concepts Breakdown
1 Bacteria And Viruses
Students must know the structural and functional differences between bacteria (prokaryotes) and viruses (non-living particles). Bacteria are single-celled organisms that can reproduce independently, while viruses require a host cell to replicate. Understanding how antibiotics target bacteria but not viruses is essential for exam questions.
Key Points
- Bacteria are prokaryotic: no membrane-bound nucleus, have cell wall, ribosomes, and can reproduce by binary fission
- Viruses are not cells: composed of genetic material (DNA or RNA) enclosed in a protein coat (capsid); some have a lipid envelope
- Antibiotics disrupt bacterial cell walls or ribosomes — they have NO effect on viruses
- Viruses replicate by injecting genetic material into a host cell and hijacking its machinery (lytic vs. lysogenic cycles)
A patient has a sore throat. The doctor determines it is caused by Streptococcus bacteria. Which treatment is appropriate — antibiotics or antivirals? Explain why the same treatment would NOT work if the cause were influenza virus.
Antibiotics are appropriate because Streptococcus is a bacterium; antibiotics can target its cell wall or protein synthesis. Influenza is a virus and lacks the bacterial structures antibiotics act on, so antibiotics would be ineffective. An antiviral or supportive care would be needed for the viral infection instead.
2 Immune Response
Students must distinguish between the non-specific (innate) immune response and the specific (adaptive) immune response. The adaptive response involves B cells producing antibodies and T cells attacking infected cells, and it produces immunological memory. Vaccination works by triggering this memory response without causing disease.
Key Points
- Non-specific defenses include skin, mucus, fever, and phagocytes (neutrophils, macrophages) — they respond to any pathogen
- Specific immune response: B lymphocytes produce antibodies (humoral immunity); T lymphocytes destroy infected cells (cell-mediated immunity)
- Antigens are markers on pathogens; antibodies are proteins that bind to specific antigens and neutralize or flag pathogens for destruction
- Memory B and T cells persist after infection, allowing a faster, stronger response upon re-exposure (basis of vaccination)
A person is exposed to chickenpox (varicella virus) for the first time and becomes ill. Years later, they are exposed again but do not get sick. Using your knowledge of the immune system, explain why.
During the first infection, the adaptive immune system produced antibodies and memory B and T cells specific to the varicella virus antigens. Upon second exposure, these memory cells rapidly recognized the antigen and mounted a faster, stronger immune response. The virus was neutralized before it could replicate enough to cause symptoms.
3 Infectious Diseases
Students must understand how infectious diseases are transmitted, how pathogens cause harm, and how the spread of disease can be controlled at the individual and population level. Knowing the difference between epidemic, pandemic, and endemic is commonly tested. Students should also understand the role of herd immunity.
Key Points
- Pathogens include bacteria, viruses, fungi, protists, and parasites — each requires different treatments
- Transmission routes: direct contact, droplets, airborne, vector-borne (e.g., mosquitoes), contaminated food/water
- Herd immunity occurs when enough of a population is immune (through vaccination or prior infection) to prevent widespread transmission, protecting those who cannot be vaccinated
- An epidemic is a disease outbreak in a region; a pandemic is a global epidemic; endemic means the disease is consistently present at baseline levels in a population
In a school of 500 students, 80% are vaccinated against measles. An unvaccinated student contracts measles. Will the disease likely spread through the school? Explain using the concept of herd immunity.
Measles requires approximately 95% vaccination coverage to achieve herd immunity, so at 80% the population is below the threshold. This means there are enough susceptible individuals for the disease to potentially spread from person to person. The unvaccinated student poses a risk not only to other unvaccinated students but also to immunocompromised individuals who cannot receive vaccines.
Questions, answered.
What is Microbiology and Disease?
Microbiology and Disease is Unit 10 of Biology, covering bacteria and viruses, immune response and infectious diseases.
How to study for Biology Unit 10?
Start with the Quick Summary above, review the Key Concepts, then test yourself with our interactive study games. Aim for 80%+ accuracy before moving on.
How many questions are in this unit?
This unit has 27+ review questions across 5 different game modes.