What is meant by a pathogen in the context of disease?
Microorganism
Includes bacteria, viruses, fungi and protoctists that cause disease.
How are pathogens commonly transmitted between individuals?
Direct and indirect transmission
Direct = contact; indirect = vectors, air, water or surfaces.
What type of transmission occurs when pathogens spread via droplets in the air?
Airbone transmission
e.g. coughing or sneezing releases infectious droplets.
What is the role of a vector in disease transmission?
Carrier organism
Often an insect that transfers pathogens between hosts.
True or False:
Pathogens can only enter the body through ingestion.
False
Entry routes include inhalation, skin breaks and mucous membranes.
What physical barrier prevents many pathogens from entering the body?
Skin
Acts as a mechanical barrier and produces antimicrobial secretions.
What substance in tears and saliva helps destroy bacteria?
Lysozyme
Breaks down bacterial cell walls.
Describe the first step of phagocytosis by a white blood cell.
Recognition and binding
Phagocyte identifies foreign antigens on pathogen surface.
What happens after a pathogen is engulfed during phagocytosis?
Phagosome formation
The pathogen is enclosed in a vesicle inside the cell.
How is a pathogen destroyed inside a phagocyte?
Lysosomal enzymes
Lysosomes release enzymes that digest the pathogen.
Fill in the blanks:
The display of pathogen antigens on a phagocyte surface is called _____ _____.
antigen presentation
Links innate and adaptive immune responses.
What type of lymphocyte is responsible for producing antibodies?
B cell
Differentiates into plasma cells to secrete antibodies.
Outline the process of clonal expansion in immune response.
Rapid cell division
Specific lymphocytes replicate after antigen recognition.
What is the function of antibodies in defending against pathogens?
Bind antigens
Leads to neutralisation, agglutination or marking for destruction.
True or False:
Memory cells enable a faster secondary immune response.
True
They remain in the body after initial infection.
Why is the secondary immune response more effective than the primary response?
Faster and greater antibody production
Due to memory cells recognising the antigen quickly.
Describe how vaccination leads to immunity.
Exposure to antigens
Stimulates memory cell formation without causing disease.
What is herd immunity and how does it reduce disease spread?
- Population-level protection
- High vaccination rates limit transmission opportunities.
Explain step-by-step how a virus infects a host cell.
Attachment → entry → replication → assembly → release
Viruses hijack host machinery to reproduce.
Why are antibiotics ineffective against viruses?
Viruses lack cellular targets for antibiotics.
They don’t have metabolic processes that antibiotics target.
True or False:
Inflammation is part of the specific immune response.
False
It is a non-specific (innate) response.
How does antigen variability in pathogens impact disease control?
It evades immune recognition.
This complicates vaccine development.
What is the significance of cell signalling in immune responses?
Activates immune cells
Coordinates defence mechanisms across the body.
Describe how barriers, phagocytes, and lymphocytes work together in defense.
They form a layered defense system:
- Barriers: prevent entry
- Phagocytes: act quickly (innate response)
- Lymphocytes: provide specific response (adaptive response).
Physical barriers prevent entry, innate response acts quickly, adaptive response is specific.
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1: Biological Molecules138
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1: Enzymes & Digestion16
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1: Cells & Ultrastructure52
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1: Transport Across Membranes20
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1: Cell Division20
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2: Exchange & Transport Systems76
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2: Plant Transport20
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2: Immune System36
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3: DNA & Protein Synthesis27
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3: Genetic Diversity14
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3: Biodiversity & Classification32
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3: Investigating Diversity12
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4: Natural Selection & Evolution42
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4: Populations & Ecosystems24
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4: Energy Transfer in Ecosystems35
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5: Photosynthesis23
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5: Respiration17
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5: ATP & Energy Transfer11
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6: Homeostasis57
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6: Nervous Coordination53
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6: Stimuli & Response62
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6: Muscles14
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7: Inheritance12
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7: Populations (Hardy–Weinberg)15
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8: Gene Mutations & Expression58
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8: Gene Technologies & Genomics46
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8: Disease24
