Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AS Biology > Chapter 12 - Communicable Diseases > Flashcards

Chapter 12 - Communicable Diseases Flashcards

1
Q

What are communicable diseases?

A

Diseases that can be passed from one organism to another, of the same or different species

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

What are communicable diseases caused by?

A

Infective organisms called ‘pathogens’

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

What are pathogens?

A

Microorganisms that cause disease

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

What are the types of pathogens? (4)

A
  • Bacteria
  • Viruses
  • Fungi
  • Protoctista
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are vectors?

A

A living or non-living factor that transmits a pathogen from one organism to another, e.g. malaria mosquito

  • Common vectors include water and insects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe bacteria

A

Prokaryotes, so have no membrane-bound nucleus or organelles

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

What are the 2 main ways of classifying bacteria?

A

By basic shapes:

  • Bacilli
  • Cocci
  • Vibrios
  • Spirilla
  • Spirochaetes

By cell walls under gram-staining

  • Gram positive bacteria look purple-blue e.g. MRSA
  • Gram negative bacteria look red e.g. E.coli
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are antibiotics?

A

A chemical or compound that kills or inhibits the growth of bacteria

  • The type of cell wall of the bacteria reactive to different antibiotics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are viruses?

A
  • Non-living infectious agents
  • 0.02-0.3 μm in diameter, so 50x smaller than the average bacterium
  • Considered by many scientists to be the ultimate parasite
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe viruses

A
  • Basic structure is genetic material (DNA or RNA) surrounded by protein
  • Invade living cells where the genetic material of the virus takes over the biochemistry of the host cell to make more virsuses
  • All natural viruses are pathogenic - they cause disease in every other type of organism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are bacteriophages?

A

Viruses that attack bacteria

  • Take over the bacteria cells and use them to replicate, destroying the bacteria at the same time
  • Can be used to identify and treat some disease, and are very important in scientific research
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are protoctista?

A

A group of eukaryotic organisms with a wide variety of feeding methods. Include single-celled organisms and cells group colonies

  • A small percentage of protoctista act as pathogens, causing diseases in both plants and animals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the protists that cause disease

A

They are parasitic - they use people or animals as their host organism

  • Pathogenic protists may need a vector to transfer them to their hosts e.g. malaria and sleeping sickness
  • May enter the body directly through polluted water e.g. amoebic dysentery and Giardia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are fungi?

A

Eukaryotic organisms that are often multicellular, although yeasts which cause human diseases e.g. thrush are single-celled

  • Cannot photosynthesise and digest their food extracellularly before absorbing nutrients
  • Many are saprophytes (feed on dead and decaying matter)
  • Some are parasitic (feeding on living plants and animals)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the fungi that cause disease

A

Fungal diseases are not a major problem in animals, but they can cause devastation in plants

  • Pathogenic fungi which cause communicable diseases are parasitic
  • They often affect the leaves of plants, stopping them photosynthesising, which quickly kills the plant
  • When fungi reproduce, they produce millions of spore which can spread huge distances, allowing them spread rapidly and widely through crop plants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the mode of action of viruses?

A

Damaging the host tissues directly

  • Viruses take over the cell metabolism
  • The viral genetic material gets into the host cell and is inserted into the host DNA
  • The host cell is used to make new viruses which the burst out of the cell, destroying it, and then spread to infect other cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the mode of action of protoctista?

A

Damaging the host tissues directly

  • Take over cells and break them open as the new generation emerge, but don’t take over the genetic material of the cell
  • Digest and use the cell contents as they reproduce e.g. protoctists which cause malaria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the mode of action of fungi?

A

Damaging the host tissues directly, and producing toxins which damage host tissues

  • Digest living cells and destroy them
  • This combined with the response of the body to the damage caused by the fungus gives the symptoms of disease
  • Some fungi also produce toxins which affect the host cells and cause disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the mode of action of bacteria?

A

Producing toxins which damage host tissues

  • Some bacterial toxins damage the host cell by breaking down the cell membranes
  • Some damage or inactivate enzymes
  • Some interfere with the host cell genetic material so that the cells cannot divide
  • These toxins are a by-product of the normal functioning of the bacteria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

List 4 examples of plant diseases

A
  • Ring rot (bacterial)
  • Tobacco mosaic virus (TMV)
  • Potato blight (protoctist)
  • Black Sigatoka (fungal)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe ring rot

A
  • Bacterial disease of potatoes, tomatoes and aubergines
  • Caused by the gram positive bacterium Clavibacter michiganesis
  • Damages leaves, tubers and fruit
  • Can destroy 80% of the crop and there’s no cure
  • Once infected, field can’t be used to grow potatoes again for 2 years
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe Tobacco Mosaic Virus (TMV)

A
  • Virus that infects tobacco plants, tomatoes, peppers, cucumbers, petunias, and delphiniums
  • Damages leaves, flowers and fruit, stunting growth and reducing yields
  • Resistant crop strains are available but there is no cure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe potato blight

A
  • AKA tomato blight, late blight
  • Caused by the fungus-like protoctist oomycete Phytophthora infestans
  • Hyphae penetrate host cells, destroying leaves, tubes and fruit
  • No cure but resistant strains, careful management and chemical treatments can reduce infection risk
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe Black Sigatoka

A
  • Banana disease caused by the fungus Mycosphaerella fijiensis, which attacks and destroys leaves
  • They hyphae penetrate and digest the cells, turning the leaves black
  • No cure, but resistant strains are being developed, and good husbandry and fungicide can control the spread of the disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

List 7 examples of animal diseases

A
  • Tuberculosis (TB)
  • Bacterial meningitis
  • HIV/AIDS
  • Influenza (flu)
  • Malaria
  • Ring worm
  • Athlete’s foot
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe tuberculosis (TB)

A

Bacterial disease

  • Humans, cows, pigs, badgers and deer
  • Caused by; Mycobacterium tuberculosis and M. bovis
  • Damages and destroys lung tissue and suppress the immune system
  • Curable by antibiotics, and preventable by improving living standards and vaccination
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe bacterial meningitis

A

Bacterial infection of the meninges of the brain

  • Can spread to the rest of the body causing septicaemia (blood poisoning) and rapid death
  • Many affects very young children and teenagers
  • Symptoms: blotchy red/purple rash that doesn’t disappear when a glass is pressed against it
  • Antibiotics cure it if delivered early
  • Vaccines protect against some forms of it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Describe HIV/AIDS

A

AIDS (acquired immunodeficiency syndrome) is caused by HIV (human immunodeficiency virus)

  • Targets T helper cell in the immune system of the body
  • Gradually destroys the immune system, so affect people of open to other infections e.g. TB, pneumonia, and some types of cancer
  • Affects humans and some non-human primates
  • No vaccine and no cure, by anti-retroviral dress slow the progress of the disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does HIV attack the body?

A

HIV is a retrovirus with RNA as its genetic material

  • Contains the enzyme reverse transcriptase, which transcribes the RNA to a single strand of DNA to produce a single strand of DNA in the host cell
  • This DNA interacts with the genetic material of the host cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How is HIV spread?

A

The virus is passed from one person to another in bodily fluids e.g. unprotected sex, shared needles, contaminated blood products, and from mother to child during pregnancy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Describe influenza (flu)

A

Viral infection

  • Can be fatal to young children, old people, and people with chronic illnesses
  • Affects mammals including humans, pigs, birds (inc. chickens)
  • 3 Strains (A,B,C); A are the most virulent
  • Flu viruses mutate regularly
  • Vulnerable groups are given a vaccine annually to protect against changing strains
  • No cure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How does influenza (flu) attack the body?

A
  • Kills the ciliated epithelial cells in the gas exchange system, leaving the airways open to secondary infection
  • Many of the deaths are from severe secondary bacterial infection on top of the original viral infections e.g. pneumonia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe ring worm

A

Fungal disease

  • Mammals including cattle, dogs, cats and humans
  • Different fungi affect different species
  • Causes grey-white, crusty, infectious circular areas of skin
  • Not damaging, but looks unsightly and may be itchy
  • Anti fungal creams are an effective cure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Describe Athlete’s foot

A

Human fungal disease

  • Caused by Tinia pedia, a form of human ring worm that grows on and digests the warm, moist skin between the toes
  • Causes cracking and scaling, which is itchy and may become sore
  • Anti fungal creams are an effective cure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Describe malaria

A

Caused by the protoctista Plasmodium, and spread by the bites of infected female Anopheles mosquitoes

  • No vaccine, limited cures
  • Killing the mosquito through insecticides
  • Removing standing water, mosquito nets, wind and door screen, long sleeved clothing etc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

How does malaria attack the body?

A
  • Plasmodium parasite has a complex life cycle with two hosts - mosquitoes and people
  • Reproduce inside the female mosquito
  • The female needs to take two blood meals to provide her with protein before she lays her eggs - this is when Plasmodium is passed onto people
  • Invades red blood cells, liver and brain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is direct transmission (animals)?

A

When a pathogen is transferred directly from one individual to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are the 3 mechanisms of direct transmission in animals?

A
  • Direct contact (contagious diseases)
  • Inoculation
  • Ingestion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Describe direct contact

A

Direct transmission in animals
Contagious diseases

  • Kissing or any contact with the body fluids of another person e.g. bacterial meningitis and many STDs
  • Direct skin-to-skin contact, e.g. ring worm, athlete’s foot
  • Microorganisms from faeces transmitted not the hands, e.g. diarrhoea diseases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Describe inoculation

A

Direct transmission in animals

  • Through a break in the skin, e.g. during sex (HIV/AIDS)
  • From an animal bite (e.g. rabies)
  • Through a puncture wound on through sharing needles, e.g. septicaemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Describe ingestion

A

Direct transmission in animals

  • Taking in contaminated food or drink, or transferring pathogens to the mouth from the hands, e.g. amoebic dysentery, diarrhoeal diseases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is indirect transmission?

A

Where the pathogen travels from one individual to another indirectly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What are the 4 types of indirect transmission in animals?

A
  • Fomites
  • Droplet infection (inhalation)
  • Vectors
  • Transmission between animals and humans
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Describe fomites

A

Indirect transmission in animals

  • Inanimate object e.g. bedding, socks or cosmetics, can transfer pathogens such as athlete’s foot, gas gangrene, and Staphylococcus infections
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Describe droplet infection (inhalation)

A

Indirect transmission in animals

  • Minute droplets of saliva and mucus expelled from the mouth as you talk, cough or sneeze
  • If droplets contain pathogens, when healthy individuals breathe them in, they may become infected e.g. TB, influenza
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Describe vectors

A

Indirect transmission in animals

  • Transmit communicable pathogens between hosts
  • e.g. mosquitoes transmit malaria, rat fleas transmit bubonic plague, dogs, foxes and bats transmit rabies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Describe transmission between animals and humans

A

Indirect transmission in animals

Between animals and humans

  • e.g. Bird flu strain H1N1, and brucellosis (sheep to people)
  • Minimising close contact with animals and washing hands
  • Vice versa e.g. foot-and-mouth disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What are the factors affecting the transmission of communicable diseases in animals? (7)

A
  • Overcrowded living and working conditions
  • Poor nutrition
  • Compromised immune system, e.g. having HIV/AID, or needing immunosuppressant drugs after transplant surgery
  • (in humans) Poor disposal of waste, providing breeding sites for vectors
  • Climate change - can introduce new vectors and diseases, e.g. increased temperatures promote the spread of malaria
  • Culture and infrastructure - in many countries, traditional medical practises can increase transmission
  • Socioeconomic factors - e.g. lack of trained health workers and insufficient public waning when there is an outbreak of disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What is direct transmission in plants?

A

The direct contact of a healthy plant with any part of a diseased plant

  • e.g. TMV, tomato and potato blight, and black Sigatoka
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What are the types of indirect transmission in plants? (2)

A
  • Soil contamination
  • Vectors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Describe soil contamination

A

Indirect transmission in plants

  • Infected plants often leave pathogens (bacteria or viruses), or reproductive spores from protoctista or fungi in the soil
  • Theses can infect the next crop
  • e.g. black Sigatoka spores, ring rot bacteria, spores of P. infestans, and TMV
  • Some pathogens (often as spores) can survive the composting process, so the infection cycle can be completed when contaminated compost is used
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What are the 4 vectors for indirect transmission of disease in plants?

A
  • Wind
  • Water
  • Animals
  • Humans
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Describe wind as a vectors for indirect transmission of disease in plants

A
  • Bacteria, viruses and fungal or oomycete spores may be carried on in the wind
  • e.g. Black Sigatoka blown between Caribbean islands, P. Infestans sporangia form spores, which are carried by the wind to other potato crops/ tomato plants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Describe water as a vector for indirect transmission of disease in plants

A
  • Spores swim in the surface film water on leaves
  • Raindrop splashes carry pathogens and spores etc
  • e.g. spores of P. infestans (potato blight) which swim over films of water on leaves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Describe animals as vectors for indirect transmission in plants

A
  • Insects and birds carry pathogens and spores from one plant to another as they feed
  • Insects such as aphids inoculate pathogens directly into plant tissues
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Describe humans as vectors for indirect transmission of disease in plnats

A
  • Pathogens and spores are transmitted by hands, clothing, fomites, farming practices and by transporting plants and crops around the world
  • e.g. TMV survives for years in tobacco products
  • Ring rot survive on farm machinery, potato sacks etc.
57
Q

What are the factors affect the transmission of communicable diseases in plants? (5)

A
  • Planting varieties of crops that are susceptible to disease
  • Over-crowding increases the likelihood of contact
  • Poor mineral nutrition reduces resistance of plants
  • Damp, warm conditions increase the survival and spread of pathogens and spores
  • Climate change - increased rainfall and wind promote the spread of diseases; changing conditions allow animal vectors to spread to new areas; drier conditions may reduce the spread of disease
58
Q

Give basic ways in which plants defend themselves against pathogen (3)

A
  • Waxy cuticle of leaves
  • Bark on trees
  • Cellulose cell walls of individual cells

All act as barriers preventing pathogens from getting in

59
Q

What is the difference between plant and animal responses to diseased tissue?

A

Unlike animals, plants don’t heal diseased tissue - they seal it off and sacrifice it

  • Because they are continually growing at the meristems, they can then replace the damaged parts
60
Q

How do plants recognise an attack?

A
  1. Receptors in the cells respond rapidly to pathogen attacks
  2. Receptors in the cells respond to molecules from the pathogens, or to chemicals produced when the plant cell wall is attacked
  3. This stimulates the release of signalling molecules that appear to switch on genes in the nucleus
  4. This triggers cellular responses including:
  • Producing defensive chemicals
  • Sending alarm signals to unaffected cells to trigger their defences
  • Physically strengthening the cell walls
61
Q

What is callose?

A

A polysaccharide containing ß 1-3 linkages and ß 1-6 linkages between the glucose monomers that is important in the plant response to infection

62
Q

What role does callose play in plant physical defences?

A

Callose papillae:

  • Within minutes of an initial attack callose is synthesised and deposited between the cell walls an cell membrane in the cells adjacent to infected cells
  • These act as barriers, preventing the pathogens entering the plant cells around the site of infection

Also:

  • Large amounts of callose continue to be deposited in cell walls after the initial infection. Lignin is added, making the mechanical barrier to invasion even thicker and stronger
  • Callose blocks sieve plates in the phloem, sealing off the infected part and preventing the spread of pathogens
  • Callose is deposited in the plasmodesmata between infected cells and their neighbours, sealing them off from the healthy cells and helping to prevent the pathogen spreading
63
Q

What happens in xylose formation?

A

This is when the xylem is blocked from carrying water by a terpene-filled swelling called a xylose. This prevents pathogens moving through the xylem

64
Q

Give examples of plant chemical defences (6)

A
  • Insect repellents e.g. pine resin and citronella from lemon grass
  • Insecticides e.g. pyrethrins (made by chrysanthemums and act as insect neurotoxins) and caffeine (toxic to insects and fungi)
  • Antibacterial compounds including antibiotics
  • Antifungal compounds
  • Anti-oomycetes e.g. glucanases (enzymes made by some plants that break down glucans; polymers found in the cell walls of oomycetes e.g. P. infestans)
  • General toxins - some plants make chemicals that can be broken down to form cyanide compounds when the plant is attacked
65
Q

Describe the antibacterial compounds made by plants

A
  • e.g. phenols - antiseptics made in many different plants
  • Antibacterial gossypol produced by cotton
  • Defensins - plant proteins that disrupt bacterial and fungal cell membranes
  • Lysosomes
66
Q

Describe the antifungal compounds made by plants

A
  • e.g. phenols - antifungals madden many different plants
  • Antifungal gossypol produced by cotton
  • Caffeine - toxic to fungi and insects
  • Saponins - chemicals in many plant cell membranes that interfere with fungal membranes
  • Chitinases - enzymes that break down the chitin in fungal cell walls
67
Q

Describe what animal non-specific responses are

A
  • Always present or activated very rapidly
  • Defends against all pathogens in the same way
68
Q

What are 4 non-specific defences keeping pathogens out?

A

Skin

  • Covers the body and prevents the entry of pathogens
  • Skin flora: healthy microorganisms that outcompete pathogens for space on the body surface
  • Produces sebum - oily substance stops the growth of pathogens

Mucous membranes

  • Lines many of the body tracts, including the airways of the gas exchange system
  • Secrete sticky mucus
  • Traps microorganisms and contains lysozymes, which destroy bacterial and fungal cell walls
  • Also contains phagocytes, which remove remaining pathogens
  • Lysozymes in tears, urine and stomach acid also help to prevent pathogens entering the body

Expulsive reflexes:

  • coughs and sneezes eject pathogen-laden much from the gas exchange system
  • Vomiting and diarrhoea expel the contents of the gut along with any infective pathogens
69
Q

What happens when you cut yourself?

A
  • The skin breached and pathogens can enter the body
  • The blood clots rapidly to seal the wound
  • When platelets come into contact with collagen in skin or the wall of the damaged blood vessel, they adhere and begin secreting several substances
70
Q

What are the substances secreted by platelets?

A
  • Thromboplastin - an enzyme that triggers a cascade of reactions resulting in the formation of a blood clot (or thrombus)
  • Serotonin - makes the smooth muscle in the walls of the blood vessels contract, so they narrow and reduce the supply of blood to the area
71
Q

What happens to the clot after thromboplastin and serotonin have been secreted by platelets?

A
  1. The clot dries out forming a hard, tough scab that keeps pathogens out
  2. Epidermal cells below the scab begin to grow, sealing the wound permanently, while damaged blood vessels regrow
  3. Collagen fibres are deposited to give the new tissue strength
  4. Once the new epidermis reaches a normal thickness, the scab sloughs off, and the wound is healed
72
Q

What is an inflammatory response?

A

A localised response to pathogens (or damage or irritants) resulting in an inflammation at the site of a wound

  • Inflammation - biological response of vascular tissues to pathogens, damaged cell or irritants, resulting in pain, heat, redness and swelling
73
Q

Describe the steps in an inflammatory response

A
  1. Mast cells are activated in damaged tissue and release chemicals called histamines and cytokines
  2. Histamines make the blood vessels dilate, causing localised heat and redness. The raised temperature helps prevent pathogens from reproducing
  3. Histamines make blood vessel walls more leaky, so blood plasma is forced out. This tissue fluid causes swelling (oedema) and pain
  4. Cytokines attract phagocytes to the site, and dispose of pathogens by phagocytosis

Widespread infections can cause a whole body rash

74
Q

What are the non-specific defence methods for getting rid of pathogens? (3)

A
  • Fevers
  • Phagocytosis
  • Helpful chemicals
75
Q

Describe fevers

A

When a pathogen invades the body, cytokines stimulate your hypothalamus to reset the thermostat and your temperature goes up

  • Higher temperatures inhibit pathogen reproduction
  • The specific immune system works faster at higher temperatures
76
Q

What is phagocytosis?

A

The process by white white blood cells called phagocytes recognise non-self cells, engulf them, and digest them within a vesicle called a phagolysosome

  • Phagocytes build up at the site of an infection and attack pathogens
  • Pus consists of dead neutrophils and pathogens
77
Q

What is a phagosome?

A

The vesicles which a pathogen or damaged cell is engulfed by a phagocyte

78
Q

What are the stages of phagocytosis?

A
  1. Pathogens produce chemicals that attract phagocytes
  2. Phagocytes recognise non-human proteins on the pathogen. This is a respondent to a specific type of pathogen, but simply a cell or organism that is non-self
  3. The phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
  4. The phagosome combines with a lysosome to form a phagolysosome
  5. Enzymes from the lysosome digest and destroy the pathogen
79
Q

What happens when a macrophage has digested a pathogen?

A
  1. It combines antigens from the pathogen surface membrane with special glycoproteins in the cytoplasm called the major histocompatibility complex (MHC)
  2. The MHC complex movs these pathogen antigens to the macrophage’s own surface membrane, becoming an antigen-presenting cell (APC)
  3. These antigens now stimulate other cells involved in the specific immune system response
80
Q

What are the helpful chemicals in non-specific immune defence? (2)

A
  • Cytokines
  • Opsonins
81
Q

How do cytokines help?

A
  • Phagocytes that have engulfed a pathogen produce chemicals called cytokines
  • Cytokines act as cell-signalling molecules, informing other phagocytes that the body is under attack and stimulating them to move to the site of infection or inflammation
  • Cytokines can also increase body temperature and stimulate the specific immune system
82
Q

How do opsonins help?

A

**Opsonins are chemicals that bind to pathogens and tag them so they are recognised more easily by phagocytes, e.g. antibodies **

  • Phagocytes have receptors on their cell membranes that bind to common opsonins and the phagocyte then engulfs the pathogen
  • Different opsonins, but antibodies such as immunoglobulin G (IgG) and immunoglobulin M (IgM) have the strongest effect
83
Q

How can counting blood cells indicate what type of response is taking place?

A
  • Examine microscope slides of blood smears
  • Stain to show the nuclei of lymphocytes
  • Identifying the numbers of different types of lymphocytes in a blood smear indicates if a non-specific or a specific immune response is taking place
84
Q

Define antibodies

A

Y-shapes glycoproteins made by B cells of the immune system in response to the presence of an antigen

85
Q

Define antigen

A

Identifying chemical on the surface of a cell that triggers an immune response

86
Q

Define ‘antigen-antibody complex’

A

The complex formed when an antibody binds to an antigen

87
Q

Describe the specific immune system

A

(aka active or acquired immunity)

  • Slower than non-specific responses
  • Immune memory cells mean that it reacts very quickly to a second invasion by the same pathogen
88
Q

Describe antibodies in detail

A
  • Y-shaped glycoproteins called immunoglobulins
  • Bind to a specific antigen on the pathogen or toxin that has triggered the immune response
  • Specific antibody for each antigen
  • Made up of two identical long polypeptide chains called heavy chains, and two much shorter chains called the light chains
  • The chains are held together by disulphide bridges, and there are also disulfide bridges within the polypeptide chains holding them in shape
89
Q

How do antibodies bind to antigens?

A

With a protein-based ‘lock-and-key’ mechanism similar to the complementarity between the active site of the enzyme and its substrate

  • Binding site is an area of 110 amino acids on both the heavy and the light chains known as the variable region
  • Variable region is a different shape on each antibody and gives the antibody its specificity
  • The rest of the antibody molecule is always the same, so is called the constant region
90
Q

What happens when an antibody binds to an antigen?

A

It forms an antigen-antibody complex

  • The hinge region of the antibody provides the molecule with flexibility
  • This allows it to bind to 2 separate antigens, one at each of its antigen-binding sites
91
Q

Give 3 ways antibodies defend the body

A
  1. The antibody of the antigen-antibody complex acts as an opsonin so the complex is easily engulfed and digested by phagocytes
  2. Most pathogens can no longer effectively invade the host cells once they are part of an antigen-antibody complex
  3. Antibodies act as agglutinins causing pathogens carrying antigen-antibody complexes to clump together. This helps prevent them spreading through the body and makes it easier for phagocytes to engulf a number of pathogens at the same time
92
Q

What are agglutinins?

A

Chemicals (antibodies) that cause pathogens to lump together so they are eager for phagocytes to engulf and digest

93
Q

What are lymphocytes

A

White blood cells that make up the specific immune system

  • B lymphocytes mature in the Bone marrow
  • T lymphocytes mature in the Thymus gland
94
Q

What are the 4 types of T lymphocytes?

A
  • T helper cells
  • T killer cells
  • T memory cells
  • T regulatory cells
95
Q

Describe T helper cells

A
  • Have CD4 receptors on cell-surface membranes, which bind to the surface antigens on APCx
  • Produce interleukins (type of cytokine)
  • The interleukins made stimulate the activity of B cells, which increases antibody production, stimulates production of other types of T cells, and attracts and stimulates macrophages to ingest pathogens with antigen-antibody complexes
96
Q

Describe T killer cells

A
  • Destroy the pathogen carrying the antigen
  • Produce a chemical called perforin, which kills the pathogen by making holes in the cell membrane so it is freely permeable
97
Q

Describe T memory cells

A
  • Live for a long time and are part of the immunological memory
  • If they meet an antigen a second time, they divide rapidly to form a huge number of clones of T killer cells that destroy the pathogen
98
Q

Describe T regulator cells

A
  • Suppress the immune system, acting to control and regulate it
  • Stop the immune response once a pathogen has been eliminated
  • Makes sure the body recognises self antigens and doesn’t set up an autoimmune response
  • Interleukins are important in this control
99
Q

What are the 3 types of B lymphocyte?

A
  • Plasma cells
  • B effector cells
  • B memory cells
100
Q

Describe plasma cells

A
  • Produce antibodies to a particular antigen and release them into the circulation
  • An active plasma cell only lives for a few days
  • Produces around 2000 antibodies per second whilst alive and active
101
Q

Describe B effector cells

A

These divide to form the plasma cell clones

102
Q

Describe B memory cells

A
  • Live for a very long time and provide the immunological memory
  • Programmed remember a specific antigen and enable the body to make a very rapid response when a pathogen carrying that antigen is encountered again
103
Q

What happens in cell-mediated immunity?

A

T lymphocytes respond to the cells of an organism that have been changed in someway, e.g. by a virus infection, by antigen processing or by mutation (e.g. cancer cells) and cells from transplanted tissue

104
Q

When is the cell-mediated response particularly important?

A

Against viruses and early cancers

105
Q

What are the stages in cell-mediated immunity?

A
  1. In the non-specific defence system, macrophages engulf and digest pathogens in phagocytosis. They process the antigens from the surface of the pathogen to form APCs
  2. The receptors on some the T helper cells fit the antigens. These cells become activated and produce interleukins which stimulate more T cells to divide by mitosis. They form clones of activated T helper cells that all carry the right antigen to bind to a particular pathogen
  3. The cloned T cells may:
  • Develop into T memory cells
  • Produce interleukins that stimulate phagocytosis
  • Produce interleukins that stimulate B cells to dive
  • Stimulate the development of a clone of T killer cells that are specific for the presented antigen and then destroy infected cells
106
Q

What happens in humoral immunity?

A

The body responds to antigens found outside the cells e.g. bacteria and fungi, and to APCs

  • The humoral immune system produces antibodies that are soluble in the blood and tissue fluid are not attached to cells
107
Q

How does humoral immunity work?

A
  • B lymphocytes have antibodies on their cell surface membrane
  • When a pathogen enters the body it will carry specific antigens, or produce toxins that act as antigens
  • A B cell with the complementary antibodies will bind to the antigens on the pathogen, or to the free antigens
  • The B cell engulfs and processes the antigens to become an APC
108
Q

What are the steps in humoral immunity?

A
  1. Activated T helper cells bind to the B cell APC. This is clonal selection - the point at which the B cell with the correct antibody to overcome a particular antigen is selected for cloning
  2. Interleukins produced by the activated T helper cells activate the B cells
  3. The activated B cell divides by mitosis to give clones of plasma cells and B memory cells. This clonal expansion
  4. Primary immune response: Cloned plasma cells produce antibodies that fir the antigens on the surface of the pathogen, bind to the antigens and disable them, or act as opsonins or agglutinins
  5. Secondary immune response: Some cloned B cells develop into B memory cells. If infected by the same pathogen again, the B memory cells die rapidly to form plasma cell clones
109
Q

What is an autoimmune disease?

A

A condition or illness resulting from an autoimmune response

110
Q

What is an autoimmune response?

A

Response when the immune system acts against its own cells and destroys healthy tissue in the body

  • Genetic tendency in some families
  • Sometimes the immune system responds abnormally to a mild pathogen or normal body microorganisms
  • In some cases the T regulator cells don’t work effectively
111
Q

What can be used to treat autoimmune diseases?

A

Immunosuppressant drugs, which prevent the immune system from working, but they also deprive the body of its natural defences against communicable diseases

112
Q

Give 3 examples of autoimmune disease

A
  • Type 1 diabetes
  • Rheumatoid arthritis
  • Lupus
113
Q

Which auto-immune disease is being referred to?

The insulin-secreting cells of the pancreas

  • Insulin injections
  • Pancreas transplants
  • Immunosuppressant drugs
A

Type 1 diabetes

114
Q

Which autoimmune disease is being referred to?

Joints-especially in the hands, wrists, ankles and feet

  • No cure
  • Anti-inflammatory drugs
  • steroids
  • Immunosuppressants
  • Pain relief
A

Rheumatoid arthritis

115
Q

Which autoimmune disease is being referred to?

Often affects skin and joints and causes fatigue. Can attack any organ in the body including kidneys, liver, lungs or brain

  • No cure
  • Anti-inflammatory drugs
  • Steroids
  • Immunosuppressants
  • Various
A

Lupus

116
Q

What is natural active immunity?

A

Immunity which results from the response of the body to the invasion of a pathogen

  • It is known as active because the body has itself acted to produce antibodies and/or memory cells
117
Q

What is natural passive immunity?

A

The immunity given to an infant mammal by the mother through the placenta and the colostrum
* Within a few days of birth, a breast-fed baby will have the same level of antibody protection against disease as the mother
* Lasts until the immune system of the baby begins to make its own antibodies
* The antibodies the baby receives from the mother are likely to be relevant to pathogens in its environment, where the mother has acquired them

118
Q

What is colostrum?

A

The first milk a mammalian mother makes

  • Very high in antibodies
  • The infant gut allows these glycoproteins to pass into the bloodstream without being digested
119
Q

What is artificial passive immunity?

A

Immunity which results from the administration of antibodies from another animal against a dangerous pathogen

  • Temporary immunity but can be lifesaving
  • e.g. used in tetanus and rabies
120
Q

How can tetanus be treated with artificial passive immunity?

A

Tetanus is caused by a toxin released by the bacterium Clostridium tetani, found in soil and animal faeces

  • Causes the muscles to go into spasm so you cannot swallow or breathe
  • People who might be infected will be injected with tetanus antibodies extracted from the blood of horses
  • This prevents the development of the disease, but doesn’t provide long-term immunity
121
Q

What is artificial active immunity?

A

Immunity which results from exposure to a safe form of a pathogen, e.g. by vaccination

  • The body is stimulated to make its own antibodies to a safe form of an antigen (a vaccine), which is injected into the bloodstream (vaccination)
122
Q

What type of pathogen may vaccines contain? (5)

A
  • Killed or inactivated bacteria and viruses, e.g. whooping cough (pertussis)
  • Attenuated (weakened) strains of live bacteria or viruses e.g. rubella, BCG against TB, polio (vaccine taken orally)
  • Toxin molecules that have been altered and detoxified, e.g. diphtheria, tetanus
  • Isolated antigens extracted from the pathogen e.g. the influenza vaccine
  • Genetically engineered antigens e.g the hepatitis B vaccine
123
Q

What are the main steps in vaccination?

A
  1. The pathogen is made safe so that the antigens are intact but there is no risk of infection
  2. Small amount of safe antigen, known as the vaccine, are injected into the blood
  3. The primary immune response is triggered by the foreign antigens and your body produces antibodies and memory cells as if you were infected with a live pathogen
  4. If you come into contact with a live pathogen, the secondary immune response is triggered and you destroy the pathogen rapidly before you suffer symptoms of the disease
124
Q

What is an epidemic?

A

When a communicable disease spreads rapidly to a lot of people at a local or national level

125
Q

What is a pandemic?

A

When a communicable disease spreads rapidly to a lot of people across a number of countries

126
Q

What is herd immunity?

A

When a significant number of people in the population have been vaccinated, this gives protection to those who do not have immunity.

This is known as herd immunity, as there is minimal opportunity for an outbreak to occur

127
Q

Give examples of diseases that cannot yet be prevented by vaccination

A

Malaria

  • Plasmodium, the protoctist that causes malaria
  • It is very evasive - spends its time inside the erythrocytes so it is protected by self antigens from the immune system, and within an infected individual, its antigens reshuffle

HIV (which causes AIDS)

  • It enters the macrophages and T helper cells, so it has disabled the immune system itself
128
Q

Describe the history of Penicillin

A

The first widely used, safe antibiotic, derived from a mould, Penicillium notatum

  • Discovered by Alexander Fleming in 1928, when he found it growing on bacteria cultures
  • Howard Florey and Ernst Chain to develop an industrial process for making the new drug, which has since saved millions of lives around the world
129
Q

How are drugs designed nowadays?

A

Using complex computer programmes
* They can build up 3D models of key molecules in the body, and of pathogens and their antigen systems
* Models of potential drug molecules are built up which are targeted at specific areas of a pathogen
* Computers are used to search through libraries of chemicals to isolate any with a potentially useful action against a specific pathogen

130
Q

What is pharmacogenomics?

A

The science of interweaving knowledge of drug actions with personal genetic material

We know that genotypes and drugs interact

131
Q

What does synthetic biology involve?

A

Using the techniques of genetic engineering, we can develop populations of bacteria to produce drugs that would otherwise be unavailable.

  • Synthetic biology enables the use of bacteria as biological factories
  • Nanotechnology is another strand of synthetic biology where tiny, non-natural particles are used for biological purposes e.g. to deliver drugs to very specific sites within the cells of pathogens or tumours
132
Q

What is selective toxicity?

A

The ability to interfere with the metabolism of a pathogen without affecting the cells of the host

  • e.g. antibiotics interfere with the metabolism of the bacteria without affecting the metabolism of the human cells
133
Q

What are antibiotic-resistant bacteria?

A

Bacteria that undergo mutation to become resistant to an antibiotic and then survive to increase in number

134
Q

How does antibiotic resistance occur in bacteria?

A

If a random mutation during bacterial reproduction produces a bacterium that is not affected by the antibiotic, that is the one which is best fitted to survive and reproduce, passing on the antibiotic resistance mutation to the daughter cells

135
Q

What are the causes for the rise in antibiotic resistance?

A
  • Over prescription of antibiotics to people
  • Adding antibiotics animal feed to prevent losing animals due to bacterial conditions and reducing business profits
136
Q

Describe MRSA

A
  • Bacterium carried by up to 30% of the population on their skin or in their nose
  • In the body it can cause boils, abscesses and potentially fatal septicaemia
  • Was treated effectively with methicillin, but a mutation has produced methicillin-resistant strains
137
Q

Describe C. difficile

A
  • Bacterium in the guts of about 5% of the population
  • Produces toxins that damage the lining of the intestines, leading to diarrhoea, bleeding and even death
  • Not a problem for healthy people, but when commonly-used antibiotics kill off much of the ‘helpful’ gut bacteria, it survives, reproduces and takes hold rapidly
138
Q

How can antibiotic-resistant infections be reduced in the long-term?

A
  • Minimising the use of antibiotics, and ensuring the every course of antibiotics is completed to reduce the risk of resistant individuals surviving and developing into a resistant strain population
  • Good hygiene in hospitals, care homes and in general - this has a major impact on the spread of all infections, including antibiotic-resistant strains
139
Q
A

AS Biology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions