A-level biology OCR > 4.1.1 Communicable diseases, disease prevention and the immune system > Flashcards

4.1.1 Communicable diseases, disease prevention and the immune system Flashcards

(159 cards)

Study These Flashcards
1
Q

What is a disease?

A

An illness or disorder of the body or mind that leads to poor health.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a communicable disease?

A

A disease caused by a pathogen that is transmissible between individuals in a population.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a non-infectious disease?

A

A long-term disease not caused by pathogens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

List the four main groups of pathogens.

A

Bacteria, viruses, fungi, protoctists.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define pathogen transmission.

A

The transfer of pathogens from an infected host to an uninfected host.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

List common modes of plant pathogen transmission.

A

Leaf-to-leaf contact, spores via wind/water, human handling, contaminated tools/soil.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

List common modes of animal pathogen transmission.

A

Direct contact, droplet infection, vectors, contaminated food or water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a vector?

A

An organism that transfers a pathogen from an infected individual to an uninfected individual.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the role of callose in plant defence?

A

Deposited in plasmodesmata and sieve plates to block pathogen spread.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is systemic acquired resistance in plants?

A

Long-term protection activated by chemical signalling in uninfected areas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is ethylene’s role in plant defence?

A

Acts as a volatile signalling molecule to trigger defences in nearby tissues or plants.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

List three physical plant defences.

A

Waxy cuticle, cellulose cell walls, bark.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is necrosis in plants?

A

Rapid death of tissue around infection site to deprive pathogens of nutrients.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are tyloses?

A

Growth of material into xylem vessels to block pathogen movement.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are passive plant defences?

A

Barriers and chemicals always present before infection.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are active plant defences?

A

Responses triggered by pathogen attack, such as callose deposition and antimicrobial compound release.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

List four primary non-specific defences in animals.

A

Skin, mucous membranes, expulsive reflexes, chemical secretions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does skin defend against pathogens?

A

Acts as a barrier; produces antimicrobial secretions; creates inhospitable environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do mucous membranes defend against pathogens?

A

Trap particles and pathogens in mucus moved by cilia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is an expulsive reflex?

A

A sneeze or cough that ejects irritants and pathogens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the role of lysozyme?

A

Enzyme that breaks down bacterial cell walls.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does stomach acid act as a defence?

A

Creates a low pH that kills ingested pathogens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are commensal microorganisms?

A

Harmless microbes that compete with pathogens for nutrients and space.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What triggers the second line of defence?

A

Pathogen entry past the first physical and chemical barriers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
List four second-line defences.
Blood clotting, inflammation, wound repair, phagocytosis.
26
Briefly describe blood clotting.
Platelets release clotting factors, fibrin forms a mesh to trap cells and seal wounds.
27
What is histamine's role in inflammation?
Causes vasodilation and increases capillary permeability.
28
What are cytokines?
Small signalling proteins that stimulate and coordinate immune responses.
29
What is chemotaxis?
Directed movement of immune cells towards a chemical signal.
30
What is a phagosome?
A vesicle containing an engulfed pathogen inside a phagocyte.
31
What is a phagolysosome?
Structure formed when a lysosome fuses with a phagosome to digest its contents.
32
What do lysosomes contain?
Hydrolytic enzymes to break down pathogens.
33
What is the role of macrophages in immunity?
Engulf pathogens and present antigens to lymphocytes.
34
What is an antigen-presenting cell?
A cell displaying pathogen antigens on MHC molecules to activate lymphocytes.
35
What is clonal selection?
Activation of specific lymphocytes with receptors complementary to a presented antigen.
36
What is clonal expansion?
Rapid mitotic division of selected lymphocytes.
37
What do T helper cells do?
Release cytokines to activate B cells and enhance phagocyte activity.
38
What do T killer cells do?
Destroy infected cells by releasing toxic substances.
39
What do T memory cells do?
Remain in the body to enable a faster secondary response.
40
What do B cells do?
Differentiate into plasma cells or memory cells after activation.
41
What do plasma cells do?
Secrete large quantities of antibodies specific to an antigen.
42
What is the primary immune response?
The initial, slower response to a first encounter with an antigen.
43
What is the secondary immune response?
A faster, stronger response due to memory cells.
44
Describe antibody structure.
Y-shaped glycoprotein with two heavy and two light chains; variable and constant regions.
45
What is the variable region of an antibody?
Binds specifically to an antigen.
46
What is the constant region of an antibody?
Binds to immune cells or molecules to trigger action.
47
What is an opsonin?
A molecule that coats a pathogen to enhance phagocytosis.
48
What is an agglutinin?
An antibody that causes pathogens to clump together.
49
What is an anti-toxin?
An antibody that neutralises toxins.
50
What is active immunity?
Immunity gained when the body produces its own antibodies after antigen exposure.
51
What is passive immunity?
Immunity gained from receiving antibodies produced by another source.
52
Give two types of active immunity.
Natural and artificial.
53
Give two types of passive immunity.
Natural and artificial.
54
What is an autoimmune disease?
A disease where the immune system attacks the body's own cells.
55
What is a vaccine?
A suspension of antigens that stimulates artificial active immunity.
56
What is herd immunity?
Protection of a population when a high proportion is immune, reducing disease spread.
57
What is ring immunity?
Vaccinating people in contact with an infected person to prevent spread.
58
What is antigenic drift?
Gradual small changes in pathogen antigens over time.
59
What is antigenic shift?
Major change in pathogen antigens that can create new strains.
60
What is antigenic concealment?
Pathogen avoiding immune detection by hiding inside cells or mimicking host molecules.
61
What is personalised medicine?
Treatment designed to match an individual’s genetic profile.
62
Why is biodiversity important for medicine?
It is a source of potential new drugs and treatments.
63
What is antibiotic resistance?
When bacteria evolve mechanisms to survive exposure to an antibiotic.
64
How does antibiotic resistance develop?
Random mutations produce resistance traits which are selected for by antibiotic use.
65
List three causes of increased antibiotic resistance.
Overuse in medicine, overuse in farming, not completing prescribed courses.
66
What is translocation in plants?
The movement of assimilates such as sucrose in phloem from sources to sinks.
67
What is a source in plant transport?
An area where assimilates are produced or released into the phloem.
68
What is a sink in plant transport?
An area where assimilates are removed from the phloem for use or storage.
69
What is active loading in phloem transport?
ATP is used to pump protons out of companion cells; sucrose enters by co-transport with protons.
70
What happens at the sink in phloem transport?
Sucrose is removed from the phloem and used or stored, lowering osmotic pressure.
71
What is phylogeny?
The evolutionary history and relationships between species.
72
How can monoculture affect plant disease spread?
Increases transmission due to high plant density and contact.
73
What are phytoalexins?
Plant-produced antimicrobial compounds that disrupt pathogen function.
74
What is the role of salicylic acid in plants?
Signals uninfected areas to activate defences.
75
What is the role of ethylene gas in plants?
Signals nearby tissues or plants to activate defence mechanisms.
76
What is the first stage of phagocytosis?
Pathogen is recognised by receptors on the phagocyte.
77
What is the second stage of phagocytosis?
Phagocyte binds to the pathogen via receptors or opsonins.
78
What is the third stage of phagocytosis?
Pathogen is engulfed by the phagocyte forming a phagosome.
79
What is the fourth stage of phagocytosis?
Lysosomes fuse with the phagosome to form a phagolysosome.
80
What is the fifth stage of phagocytosis?
Hydrolytic enzymes digest the pathogen.
81
What is the final stage of phagocytosis?
Antigen fragments are presented on the cell surface for lymphocyte activation.
82
What is the role of MHC in immunity?
Major histocompatibility complex proteins present antigens on cell surfaces.
83
What is the role of interleukins?
A type of cytokine that coordinates the activity of immune cells.
84
What is the role of chemokines?
Cytokines that attract immune cells to sites of infection.
85
What is the role of perforin?
Protein released by T killer cells that creates pores in target cell membranes.
86
What is the role of granzymes?
Enzymes released by T killer cells that enter infected cells and trigger apoptosis.
87
What is the role of the constant region of an antibody?
Determines the antibody class and binds to immune system components.
88
What is the role of the hinge region of an antibody?
Provides flexibility to bind antigens at different angles.
89
What is the light chain of an antibody?
The smaller polypeptide chain of the antibody molecule.
90
What is the heavy chain of an antibody?
The larger polypeptide chain of the antibody molecule.
91
What is neutralisation by antibodies?
Blocking of pathogen binding sites or toxin active sites.
92
What is the complement system?
A group of plasma proteins that assist antibodies and phagocytes in clearing pathogens.
93
What is the role of complement proteins?
Opsonisation, membrane attack complex formation, inflammation promotion.
94
What is immunological memory?
The ability of the immune system to respond more rapidly and effectively to pathogens it has encountered before.
95
What is the lag phase in the primary immune response?
The period before detectable antibodies are produced.
96
What is the plateau phase in the immune response?
When antibody levels remain constant before declining.
97
What is the decline phase in the immune response?
When antibody levels fall after an infection is cleared.
98
What is the main purpose of the secondary immune response?
Rapid elimination of a pathogen before symptoms develop.
99
What is natural active immunity?
Immunity gained through normal infection.
100
What is artificial active immunity?
Immunity gained through vaccination.
101
What is natural passive immunity?
Immunity gained through transfer of antibodies from mother to offspring.
102
What is artificial passive immunity?
Immunity gained through injection of pre-formed antibodies.
103
What is the principle of a vaccination programme?
To expose the immune system to antigens in a controlled way to stimulate memory cell production.
104
What is the primary goal of vaccination in public health?
To reduce incidence of disease and prevent epidemics.
105
What is booster vaccination?
An additional dose given to maintain or increase immunity.
106
Why are some vaccines reformulated annually?
To match circulating strains due to antigenic variation.
107
What is a live attenuated vaccine?
Vaccine containing a weakened form of the pathogen.
108
What is an inactivated vaccine?
Vaccine containing killed pathogens.
109
What is a subunit vaccine?
Vaccine containing only antigenic parts of a pathogen.
110
What is a toxoid vaccine?
Vaccine containing inactivated toxins.
111
What are adjuvants?
Substances added to vaccines to enhance the immune response.
112
What is cross immunity?
Protection against one pathogen due to immunity to a similar pathogen.
113
What is immunisation coverage?
The proportion of a population vaccinated.
114
What is antimicrobial chemotherapy?
Use of chemicals to control or destroy microorganisms.
115
What is the mode of action of bactericidal antibiotics?
Kill bacteria directly.
116
What is the mode of action of bacteriostatic antibiotics?
Inhibit bacterial growth and reproduction.
117
What is the role of cell wall synthesis inhibitors?
Prevent formation of bacterial cell walls causing lysis.
118
What is the role of protein synthesis inhibitors?
Prevent bacterial ribosomes from making proteins.
119
What is the role of nucleic acid synthesis inhibitors?
Prevent replication or transcription in bacteria.
120
What is selective toxicity?
Property of a drug that harms pathogens without harming the host.
121
What is antibiotic stewardship?
Set of practices to slow the development of antibiotic resistance.
122
What is combination therapy?
Using more than one antimicrobial drug to reduce resistance risk.
123
What is vertical transmission of resistance?
Passing resistance genes to offspring during reproduction.
124
What is horizontal transmission of resistance?
Passing resistance genes between bacteria by plasmids.
125
What is a reservoir of infection?
Any environment where a pathogen normally lives and reproduces.
126
What is zoonosis?
A disease that can be transmitted from animals to humans.
127
What is a notifiable disease?
A disease that must be reported to public health authorities.
128
What is the incubation period?
The time between pathogen entry and symptom onset.
129
What is the infectious period?
The time when an infected individual can transmit the pathogen.
130
What is a carrier?
An individual who harbours a pathogen without showing symptoms.
131
What is a pandemic?
An epidemic that has spread across countries or continents.
132
What is an endemic disease?
A disease constantly present in a particular area or population.
133
What is an epidemic?
A sudden increase in disease cases in a population.
134
What is innate immunity?
Non-specific defence mechanisms present from birth.
135
What is adaptive immunity?
Specific defence mechanisms that develop after exposure to antigens.
136
What is immunodeficiency?
Reduced function or absence of the immune response.
137
What is secondary immunodeficiency?
Immunodeficiency acquired during life due to disease or treatment.
138
What is the difference between humoral and cell-mediated immunity?
Humoral immunity is antibody-mediated; cell-mediated immunity is T cell-mediated.
139
What are secondary metabolites in plants?
Chemicals not directly involved in growth but used in defence.
140
What are terpenoids?
Plant secondary metabolites with antimicrobial properties.
141
What are phenols in plants?
Secondary metabolites that disrupt pathogen enzymes.
142
What are alkaloids in plants?
Bitter-tasting compounds that deter herbivores and inhibit pathogen growth.
143
What are hydrolytic enzymes in plants?
Enzymes that degrade pathogen cell walls.
144
What is oxidative burst in plants?
Rapid production of reactive oxygen species to damage pathogens.
145
What is mechanical reinforcement in plant defence?
Thickening of cell walls and lignin deposition after attack.
146
What is abscission in plant defence?
Shedding of infected leaves to remove pathogens.
147
What is quorum sensing?
Bacterial communication to coordinate behaviour such as biofilm formation.
148
What is biofilm?
A community of microorganisms embedded in a protective extracellular matrix.
149
What is antigenic variation?
Changes in pathogen antigens to evade immune detection.
150
What is latency in pathogens?
Ability to remain dormant in the host and reactivate later.
151
What is coevolution?
Reciprocal evolutionary changes in interacting species such as hosts and pathogens.
152
What is the Red Queen hypothesis?
Concept that organisms must constantly adapt to survive against evolving opponents.
153
What is the purpose of sieve plates in phloem?
To allow flow between sieve tube elements while maintaining pressure.
154
What is the function of companion cells in phloem?
Provide metabolic support for sieve tube elements.
155
What is the mass flow hypothesis?
Theory explaining translocation as movement of solutes driven by pressure differences.
156
What is phloem unloading?
Removal of assimilates from the phloem into sink tissues.
157
What is source-sink pressure gradient?
Difference in water potential driving movement in phloem.
158
What is apoplastic loading?
Movement of assimilates through cell walls into the phloem.
159
What is symplastic loading?
Movement of assimilates through cytoplasm via plasmodesmata into the phloem.
A-level biology OCR
flashcards
Decks in class (24)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions