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A Level Biology - OCR Biology A > 4.1.1 Communicable diseases > Flashcards

4.1.1 Communicable diseases Flashcards

1
Q

What is meant by the term ‘communicable disease’?

A

A disease that:
- is caused by pathogens
- can be spread/transmitted between organisms

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2
Q

Name the four types of pathogen.

A
  • Bacteria
  • Viruses
  • Fungi
  • Protists
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3
Q

Which pathogen causes tuberculosis?

A

Bacteria

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4
Q

What are some symptoms of tuberculosis?

A

Persistent cough
Chest pain
Coughing up blood or sputum
Fatigue
Weight loss
Fever
Night sweats
Loss of appetite.

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5
Q

How is tuberculosis transmitted?

A

Droplets from coughs or sneezes

Inhaling droplets that contain the bacteria

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6
Q

What are some symptoms of bacterial meningitis?

A

Sudden onset of severe headache, fever, stiff neck, sensitivity to light (photophobia), confusion, vomiting, and in severe cases, seizures or coma.

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7
Q

How is bacterial meningitis transmitted?

A

Droplets from coughs or sneezes

Inhaling droplets that contain the bacteria

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8
Q

Which pathogen causes ring rot?

A

Bacteria

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9
Q

Which type of organism is primarily affected by ring rot?

A

Tomato and potato plants

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10
Q

What are the symptoms of ring rot?

A

Yellowing and wilting of leaves, brown lesions on stems, and the formation of circular, rotten areas on fruits.

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11
Q

How is ring rot transmitted?

A

Spread through contaminated soil, water, plant debris, or infected seeds. Can also be transmitted through infected tools or by contact with infected plants.

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12
Q

Which pathogen causes AIDS?

A

Virus (HIV)

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13
Q

How is the HIV virus transmitted?

A

Spread through contact with certain bodily fluids, including blood, semen, vaginal fluids, and breast milk.

Common modes of transmission include unprotected sexual intercourse, sharing needles or syringes, and from mother to child during pregnancy, childbirth, or breastfeeding.

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14
Q

Which pathogen causes influenza?

A

Virus

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15
Q

What are some symptoms of influenza?

A

Sudden onset of fever, chills, sore throat, cough, runny or stuffy nose, muscle or body aches, fatigue, and headache. Some individuals may also experience vomiting and diarrhea.

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16
Q

How is influenza transmitted (spread)?

A

Droplets from coughs or sneezes

Inhaling droplets that contain the viral particles

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17
Q

What are some symptoms of tobacco mosaic virus?

A

Characterized by distinctive mosaic-like patterns of light and dark green on leaves, stunted growth, leaf curling, and reduced yield in infected plants.

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18
Q

Which pathogen causes black sigatoka?

A

Fungus

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19
Q

Which type of pathogen is usually affected by black sigatoka?

A

Banana plants

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20
Q

How is black sigatoka transmitted?

A

Spread through airborne spores produced by infected plants.

Warm and humid conditions promote the growth and spread of the fungus.

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21
Q

Which pathogen causes ringworm?

A

Fungus

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22
Q

What are some symptoms of ringworm?

A

Red, itchy, and raised circular patches on the skin with a clear center, which may appear scaly or crusty.

Hair loss can occur in affected areas.

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22
Q

How is ringworm transmitted?

A

Spread through direct contact with infected humans or animals, or by contact with contaminated objects such as towels, clothing, or surfaces.

Fungal spores can also survive in the environment.

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22
Q

Which type of pathogen causes athlete’s foot?

A

Fungus

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22
Q

How is athlete’s foot transmitted?

A

Spread through direct contact with contaminated surfaces, such as floors in locker rooms, showers, or swimming pool areas.

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22
Q

Which type of pathogen causes potato late blight?

A

Protist

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23
Q

How is potato late blight transmitted?

A

Spread through spores produced by infected plants, which can be carried by wind, rain, or irrigation water.

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24
Q

Which pathogen causes malaria?

A

Protist

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25
Q

What are some symptoms of malaria?

A

Fever, chills, sweating, headache, muscle aches, fatigue, and nausea.

In severe cases, malaria can lead to complications such as anaemia, jaundice, organ failure, and death.

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26
Q

How is malaria transmitted?

A

Spread through the bite of infected mosquitoes, which inject Plasmodium parasites into the bloodstream.

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27
Q

What are the three direct methods that a communicable disease can be transmitted?

A
  • Droplets
  • Sexual intercourse
  • Direct contact
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28
Q

What are the three indirect methods that a communicable disease can be transmitted?

A
  • Air
  • Water
  • Food
  • Vector
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29
Q

Why is malaria more common in tropical countries?

A

Ideal conditions for mosquitoes to breed (hot and humid)

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30
Q

What are the three physical barriers that plants have against pathogens?

A
  • Cell walls
  • Waxy cuticle in leaves
  • Callose (blocks plasmodesmata)
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31
Q

What are three primary defences against pathogens in humans?

A
  • The skin
  • Cilia / Mucus in trachea / nose
  • Expulsive reflexes
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32
Q

What are two secondary defences against pathogens in humans?

A
  • Blood clots
  • Inflammation
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33
Q

What are expulsive reflexes and what are their function?

A

Coughing and sneezing.
Removes foreign objects, including pathogens, from the airways.

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34
Q

Describe how a blood clot forms.

A

Platelets release clotting factors.
Fibrinogen is converted into an insoluble fibre, fibrin.
Fibrin forms a mesh which traps platelets and blood cells.

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35
Q

During inflammation, why does the wound site become swollen?

A

Mast cells produce histamine in response to tissue damage
The permeability of the blood vessels increases
Blood vessels leak fluid into the surrounding area
This causes swelling, which helps to isolate pathogen

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36
Q

During inflammation, why does the wound site become red and hot?

A

Mast cells produce histamine in response to tissue damage
This causes vasodilation, increasing blood flow in the capillaries
This makes the area red and hot
This also brings white blood cells to the area to fight off pathogens

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37
Q

Which type of white blood cell is this?

A

Neutrophil

38
Q

How would you describe the nucleus of a neutrophil?

A

Multi-lobed

39
Q

What is the role of cytokines in phagocytosis?

A

Chemicals released by pathogens which attract neutrophils to the site of infection

40
Q

What is the role of opsonins in phagocytosis?

A

Opsonins are chemicals that coat the pathogen, so that phagocytes can easily bind to and engulf the pathogen.

41
Q

Describe what happens to the pathogen once it is engulfed by a neutrophil.

A

The pathogen is now contained in a phagosome, which is a type of vesicle, within the cytoplasm of the neutrophil.

A lysosome fuses with the phagosome.

The lysosome contains digestive enzymes which break down the pathogen.

42
Q

After phagocytosis, what does a neutrophil become?

A

An antigen-presenting cell

43
Q

Which type of white blood cell is this?

A

Lymphocyte

44
Q

Name the two types of lymphocyte.

A

T lymphocyte (T cell)

B lymphocyte (B cell)

45
Q

Where at T lymphocytes (T cells) produced and matured?

A

T lymphocytes are:
- Produced in the bone marrow
- Matured in the thymus gland

46
Q

The receptors on the surface of a T lymphocyte bind to…

A

Antigen-presenting cells (neutrophils)

47
Q

Describe the process of clonal selection in T lymphocytes.

A

T cells with complementary receptors to the antigen are selected for replication.

48
Q

Describe the process of clonal expansion in T lymphocytes.

A

Activated T cells divide by mitosis to produce clones, each with specific roles.

49
Q

Name four types of T lymphocyte (T cell).

A
  • Killer T cell
  • Helper T cell
  • Regulatory T cell
  • Memory T cells
50
Q

What is the role of a helper T cell?

A

Releases interleukins (a type of cytokine), which activates killer T cells and B lymphocytes.

51
Q

What is the role of a killer T cell?

A
  • Binds to antigen-presenting cells
  • Releases perforins, which breaks the cell membrane of the infected cell
  • Releases toxins, which kill the infected cell and the pathogen inside
52
Q

What is the role of regulatory T cells?

A

Regulates the immune response by
- preventing T killer cells from killing uninfected cells
- shutting down the immune system once the body is cleared of the pathogen

53
Q

Describe the role of memory T cells.

A

Remain in the blood so if the same antigen is encountered again, clonal selection can occur much more quickly.

54
Q

Where are B lymphocytes produced and matured?

A

B lymphocytes are
- produced in the bone marrow
- matured in the bone marrow

55
Q

In clonal expansion, which type of cell do B lymphocytes differentiate into?

A

Plasma cells

56
Q

What is the role of plasma cells?

A

Secrete large numbers of antibodies into the blood that are specific to one type of antigen.

57
Q

What is the primary immune response?

A

When pathogens enter the body for the first time, the antigens on its surface activate the immune system.

58
Q

What is the secondary immune response?

A

If the person is exposed to a pathogen for a second time, the immune system produces a stronger and quicker response.

59
Q

What are some differences between the primary and secondary immune responses?

A
  • Primary response is slower / Secondary is faster
  • Secondary involves memory cells
  • More antibodies are produced during secondary response
  • Shorter delay between exposure to pathogen and secondary immune response
60
Q

Explain why a person does not experience symptoms during a secondary immune response.

A
  • Memory cells produce antibodies very quickly
  • Pathogen is killed before it can release toxins or damage host cells
61
Q

Which type of biological molecule is an antibody?

A

Glycoprotein

62
Q

How many polypeptide chains is an antibody made up of?

A

Four (two heavy, two light)

63
Q

How are the heavy chains in an antibody bonded together?

A

Disulfide bonds (a covalent bond linking two sulfur atoms)

64
Q

Name the two regions in an antibody.

A
  • Constant region
  • Variable region
65
Q

Explain why an antibody has a ‘variable region’.

A
  • The variable region is where an antibody attaches to the antigen
  • The variable region must have different shapes so each antibody is complementary to one specific antigen
66
Q

The hinge region allows an antibody to be flexible.
Explain why this is important.

A

Allows the antigen-binding sites to be placed at different angles so they can easily bind to antigens.

67
Q

What are the three main roles of antibodies?

A
  • Agglutinating pathogens
  • Opsonisation
  • Neutralising toxins
68
Q

Agglutinins are a type of antibody.
Describe the role of agglutinins.

A
  • Antibodies have two binding sites, so they can bind to two antigens at the same time
  • Pathogens become clumped together
69
Q

Antitoxins are a type of antibody.
Describe the role of antitoxins.

A

Bind to and neutralise toxins so they are unable to enter and damage host cells.

70
Q

Opsonins are a type of antibody.
Describe the role of opsonins.

A

Bind to pathogens, making them easily identifiable to neutrophils (phagocytes).

71
Q

When does active immunity occur?

A

When the body makes its own antibodies after being stimulated by a pathogen.

72
Q

Immunity can be active and natural.
When does this occur?

A

After exposure to a live pathogen, causing a disease

73
Q

Immunity can be active and artificial.
When does this occur?

A

After being given a vaccination (containing a harmless dose of an antigen)

74
Q

When does passive immunity occur?

A

When given antibodies made by a different organism.

75
Q

Immunity can be natural and passive.
When does this occur?

A

When a baby becomes immune due to receiving its mothers antibodies through the placenta or breastmilk.

76
Q

Immunity can be natural and artificial.
When does this occur?

A

When you become immune due to being injected with antibodies from someone else (e.g. monoclonal antibodies).

77
Q

Does active or passive immunity take longer to develop? Why?

A

Active, because it involves the primary immune response.
Lymphocytes are producing antibodies for the first time.

78
Q

Which type of immunity, active or passive, involves long-term protection? Why?

A

Active immunity, because it involves the formation of memory cells.

79
Q

When do autoimmune diseases occur?

A

When the immune system recognises the body’s own cells as foreign and attacks them.

80
Q

Give two examples of autoimmune diseases.

A
  • Lupus
  • Rheumatoid arthritis
81
Q

Which part of the body is attacked in a lupus sufferer?

A

Connective tissues

82
Q

How are autoimmune diseases treated?

A

Using immunosuppressant drugs

83
Q

What is the difference between vaccination and immunisation?

A

Vaccination involves adminstering antigens from a pathogen to somebody to stimulate an immune response.

Immunisation is the process by which you develop immunity in your body.

Vaccination causes immunisation.

84
Q

Describe the concept of herd immunity.

A

If a large proportion of the population is vaccinated, those that are unvaccinated (old, very young, immunocompromised) are less likely to catch the disease.

85
Q

What do live attenuated vaccines contain?

A

A weakened pathogen

86
Q

What are two potential challenges of giving vaccines orally?

A
  • Could be broken down / digested by enzymes in the gut
  • Could be too large to be absorbed into the bloodstream
87
Q

Why does the flu vaccine need to be given every year?

A

The influenza virus mutates regularly, and the antigens on its surface change (antigenic drift).

88
Q

Which pathogen do antibiotics kill?

A

Bacteria

89
Q

What was the first antibiotic that was developed?

A

Penicillin

90
Q

Give two risks of using anitbiotics.

A
  • Cause severe allergic reactions in some people
  • Antibiotic resistance can develop if not used correctly
91
Q

Describe how antibiotic resistance develops.

A
  • There is genetic variation in a population of bacteria
  • Genetic mutations make some bacteria naturally resistant to an antibiotic
  • When an antibiotic is introduced, resistant bacteria are more likely to survive
  • The allele for antibiotic resistance is passed to their offspring

This is an example of natural selection.

92
Q

Give two examples of ‘superbugs’ caused by antibiotic resistant bacteria.

A
  • MRSA
  • Clostridium difficile
93
Q

Name the bacteria that causes MRSA, and which antibiotic is it resistant to?

A

Caused by Staphylococcus aureus bacteria

Resistant to methicillin

94
Q

What are the symptoms of MRSA?

A

Causes serious wounds on the skin

95
Q

What are the symptoms of C difficile?

A

Severe diarrhoea, fever, cramps.

96
Q

How can we prevent antibiotic resistance from developing?

A
  • Doctors should not prescribe antibiotics for minor infections
  • Doctors should not prescribe antibiotics for viral infections
  • Patients should finish their full course of antibiotics
97
Q

What are personalised medicines?

A

Medicines that are tailored to a person’s DNA

98
Q

In theory, how could personalised medicines be developed?

A

Doctors can analyse your genetic information and use this to determine how you will respond to different drugs, only prescribing those that will be most effective for you.

A Level Biology - OCR Biology A (13 decks)

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