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Biology A-Level -James > Chapter 4.1-Communicable Diseases > Flashcards

Chapter 4.1-Communicable Diseases Flashcards

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1
Q

What is a pathogen?

A

a micro-organism that causes diseases

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2
Q

What are the 5 different pathogens that cause diseases?

A
  • bacteria
  • fungi
  • viruses
  • protoctista
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3
Q

How does bacteria cause disease?

A
  • belong to the Kingdom Prokaryotae
  • reproduce rapidly (once every 20 minutes)
  • release waste products and/or toxins that are toxic to the host
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4
Q

What are three diseases that are caused by bacteria and what are the specific names of the organisms that cause the disease?

A
  • Tuberculosis: disease that affects many parts of the body, killing the cells and tissues: the lungs are most affected. Caused by the bacteria Mycobacterium tuberculosis and M.boyls
  • bacterial meningitis: infection of the meninges-the membrane that surround the brain and spinal cord. Caused by the bacteria Neisseria meningitidis or Streptococcus pneumonia
  • ring rot in plants:ring of decay in the vascular tissue of a potato tuber or tomato, accompanied by leaf wilting. Caused by the bacteria Clavibacter michiganensis
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5
Q

How does fungi cause disease in animals?

A

fungus lives in the skin, and where its hyphae, which form a mycelium, grow under the skin surface. The fungus can send out specialised reproductive hyphae, which grow to the surface of the skin to release spores. This results in redness and irritation

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6
Q

How does fungi cause disease in plants?

A

the fungus lives in the vascular tissue, where it can gain nutrients. The hyphae release extracellular enzymes, such as celluloses, to digest the surrounding tissue which causes decay. Leaves will often become mottled in colour, curl up and shrivel, before dying.

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7
Q

What are the three diseases that are caused by fungi and what are the specific names of the organisms that cause thee diseases?

A
  • Black Sigatoka (bananas): : causes leaf spots on banana plants reducing yield. Cuaed by the fungus Mycosphaerella fijiensis
  • Ringworm (cattle):growth of fungus in skin with spore cases erupting through skin to cause a rash. Caused by a fungus called Trichophyton verrucosum
  • Athlete’s foot (humans):growth under skin of feet-particularly between the toes. Caused by the fungus Trichophyton rubrum
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8
Q

How do viruses cause disease?

A

viruses invade cells and take over the genetic machinery and other organelles of the cell. They then cause the cell to manufacture more copies of the virus. The host cell eventually bursts, releasing many new viruses which will infect healthy cells

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9
Q

What are the three diseases that are caused by viruses and what are the specific names of the organisms that cause these diseases?

A
  • HIV/AIDS: attacks cells in the immune system and compromises the immune response. It is caused by the virus human immunodeficiency virus
  • Influenza: attacks respiratory system and causes muscle pains and headaches. Caused by the virus from the family Orthomyxoviridae
  • Tobacco mosaic virus: causes mottling and discolouration of leaves. Caused by the virus tobacco mosaic virus
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10
Q

How do protoctists cause disease?

A

enter host cells and feed on the contents as they grow

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11
Q

What are the two type of diseases that are caused by protoctista and whats the name of the protoctistan that cause these diseases?

A
  • Blight (tomatoes and potatoes): affects both leaves and potato tubers. Caused by the protoctistan Phytophthora infestans
  • Malaria: headaches, fever, (coma, death). Caused by the protoctistan Plasmodium falciparum
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12
Q

What are the basic stages in the life cycle of pathogens?

A
  • travel from one host to another (transmission)
  • entering the host’s tissues
  • reproducing
  • leaving the host’s tissues
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13
Q

What is meant by transmission of pathogens?

A

passing a pathogen from an infected individual to an uninfected individual

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14
Q

What are the two types of ways that pathogens can be transmitted between animals?

A
  • direct transmission

- indirect transmission

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15
Q

What is meant by direct transmission?

A

passing a pathogen from host to new host, with no intermediary

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16
Q

What is meant by indirect transmission?

A

passing a pathogen from host to new host, via a vector

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17
Q

What is a vector?

A

an organism that carries a pathogen from one host to another

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18
Q

What type of transmission (direct or indirect) is the droplet infection and what are the factors that affect this transmission?

A
  • DIRECT transmission: pathogen is carried in tiny water droplets in the air. For example, tuberculosis, influenza
  • Catch it-bin it-kill it: cover your mouth when coughing or sneezing. Use a tissue and ensure that the tissue is disposed of correctly
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19
Q

What type of transmission (direct or indirect) is direct physical contact and what factors affect transmission?

A
  • DIRECT transmission: touching a person who is infected or touching contaminated surfaces (including soil) that harbour the pathogens. For example, HIV, bacterial meningitis, ringworm, athlete’s foot.
  • Hygiene: tasing hands regularly-especially after using the toilet. Keeping surfaces clean-especially door handles. Cleaning and disinfecting cuts and abrasions. Sterilising surgical instruments. Using condoms during sexual intercourse
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20
Q

What type of transmission (direct or indirect) is faecal-oral transmission and what factors affect this type of transmission?

A
  • DIRECT transmission: usually by eating food or drinking water contaminated by the pathogen. For example, cholera, food poisoning
  • Using human sewage to fertilise crops is a common practise in some parts of the world. Treatment of waste water and treatment of drinking water are important ways to reduce the risk. Thorough cleaning of all fresh food (using treated water). Careful preparation and thorough cooking of all food
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21
Q

What type of transmission (direct or indirect) is transmission by spores and what factors affect this type of transmission?

A
  • DIRECT transmission: resistant stage of the pathogen. These can be carried in the air or reside on surfaces or in the soil. For example, anthrax, tetanus
  • Use of a mask. Washing skin after contact with soil
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22
Q

What are the other social factors which increase the transmission of pathogens?

A
  • overcrowding-many people living and sleeping together in one house
  • poor ventilation
  • poor health
  • poor diet
  • homelessness
  • living or working with people who have migrated from areas where a disease is more common
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23
Q

How is the transmission of malaria an example of non-direct transmission?

A
  • person with malaria has the gametes of Plasmodium in blood (parasite that causes malaria)
  • Female Anopheles mosquito sucks the blood of the infected person (mosquito is the vector).
  • Plasmodium develops and migrates to a mosquito’s salivary glands
  • uninfected person is bitten and Plasmodium migrates to the liver. Plasmodium migrates to the blood and the person is now infected with malaria
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24
Q

What are examples of direct pathogen transmission in plants?

A
  • many pathogens are present in the soil and will infect plants by entering the roots
  • fungi produce spores which can be carried by the wind- airborne transmission
  • pathogens can also enter the fruit and seeds, and all then be distributed within the seeds- so that many or all of the offspring are infected.
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25
Q

What are examples of indirect pathogen transmission in plants?

A

-insect attacks: spores or bacteria become attached to a burrowing insect, such as a beetle, which attacks an infected plant. When that beetle attacks another plant, the pathogen is transmitted to the uninfected plant. The beetle is acting as a vector.

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26
Q

What are the two types of defences that plants have against pathogens?

A
  • passive defences to prevent entry

- active defences which are induced when the pathogen is detected

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27
Q

What are passive defences to pathogens in plants?

A

defences that are present before infection, and their role is to prevent entry and spread of the pathogen. Passive defences include physical barriers and chemicals

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28
Q

What are some of the passive defences that plants have to prevent pathogens from entering the plant?

A
  • ‘lost cow back’
  • Lignin thickening of the cell walls-living is waterproof and almost completely indigestible
  • Stomatal closure as this is a possible entry site for pathogens.
  • Tylose formation: a tylose is a balloon-like swelling or projection that fills the xylem vessel. When a xylose is fully formed, it plugs and the vessel can no longer carry water. Blocking the xylem vessels prevents spread of pathogens through the heartwood.
  • Cellulose cell-wall: physical barrier swell as containing a variety of chemical defences that can be activated the a pathogen is detected
  • Waxy cuticle: prevents water from collecting on the cell surfaces. Pathogens collect in water and need water to survive, the absence of water is a passive defence.
  • Bark: contains a number of different chemical defences
  • Callose:deposited in the sieve tubes at the end of a growing season. It is deposited around the sieve plates and blocks the flow in the sieve tube. This can prevent a pathogen from spreading around the plant.
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29
Q

What is a callose?

A

large polysaccharide deposit that blocks old phloem sieve tubes

30
Q

What are active defences in plants?

A
  • produced when pathogens attack
  • plants detect chemicals in pathogen’s cell walls
  • fortifies defences that are already present
31
Q

What are some of the active defences (apart from the release of chemicals) that plants carry out when they detect a pathogen?

A
  • cell wall becomes thickened and strengthened with additional cellulose
  • deposition of callose between the plant cell wall and cell membrane near the invading pathogen. Callose deposits are polysaccharides polymers that impede cellular penetration at the site of infection. It strengthens the cell wall and blocks plasmodesmata
  • oxidative bursts that produces highly reactive oxygen molecules capable of damaging the cells of invading organisms
32
Q

What is necrosis and how is it an example of a active defence by a plant?

A

-deliberate cell suicide. A few cells are sacrificed to save the rest of the plant. By killing cells surrounding the infection, the pant can limit the pathogens access to water and nutrients and can therefore stop it spreading further around the plant.

33
Q

What is a canker?

A

sunken necrotic lesion in woody tissue such as the main stem or branch. It causes death of the cambium tissue in the bark

34
Q

What are terpenoids and how do they protect plants from pathogens?

A

range of essential oils that have antibacterial and anti fungal properties. They may also create scent, for example, the menthols and mentions produced by mint plants

35
Q

What are phenols and how do they protect plants from pathogens?

A
  • antibacterial and anti fungal properties.
  • tannins found in bark inhibit attack by insects. These compounds bind to salivary proteins and digestive enzymes such as trypsin and chymotrypsin, deactivating the enzymes. Insects that ingest high amounts of tannins do not grow and will eventually die. This helps to prevent the transmission of pathogens.
36
Q

What are alkaloids and how do they protect plants from pathogens?

A
  • nitrogen-contianing compounds such as caffeine, nicotine,cocaine, morphine, solanine.
  • give a bitter taste to inhibit herbivores feeding. They also act on a variety of metabolic reactions via inhibiting or activating enzyme action. Some alkaloids inhibit protein synthesis. If the plant can reduce grazing by larger animals, then it will suffer less damage that can allow pathogens to enter the plant.
37
Q

What are defensins (defensive proteins) and how do they protect plants from pathogens?

A

small cysteine rich-proteins that have broad anti-microbial activity. They appear to act upon molecules in the plasma membrane of pathogens, possibly inhibiting the action of ion transport channels

38
Q

What are hydrolytic enzymes and how do they protect plants from pathogens?

A

found in the spaes between cells. They include chitinases (which break down the chitin found in fungal cell walls), glucanases(hydrolyse the glycosidic bonds in gluons) and lysozyme (which are capable of degrading bacterial cells walls)

39
Q

What are primary defences to pathogens in humans?

A

those that prevent pathogens entering the body

40
Q

Why are primary defences against pathogens in humans known as being non-specific?

A

all pathogens are treated in the same way by the same cells

41
Q

How does the skin act as a primary defence against pathogens?

A

-outer layer of the skin is called the epidermis, and it consists of layers of cells. Most of these cells are called keratinocytes. These cells are produced by mitosis at the base of the epidermis. They then migrate out to the surface of the skin. As they migrate, they dry out and the cytoplasm is replaced by the protein keratin. This process is called keratinisation, and usually takes about 30 days. The keratinised layer of dead cells acts as an effective barrier to pathogens

42
Q

How does blood clotting and skin repair act as a primary defence against pathogens in humans?

A
  • Mechanism that prevents excess blood loss
  • Clot acts as temporary seal
  • Prevents infection and first step in skin reparation
  • Requires calcium ions and 12 cofactors
  • Clotting factors that form the clotting cascade
  • After the clot, a scab forms, and the epidermis heals more permanently.
43
Q

What are the enzymes and ions involved in forming blood clots?

A
  • active thrombokinase and active thrombin

- Ca^2+

44
Q

What are mucous membranes?

A

specialised epithelial tissue that is covered by mucus

45
Q

How do mucous membranes prevent pathogens from teetering the body?

A
  • epithelial layer contains mucus-secreting cells called goblet cells. It also contains extra mucus-secreting glands under the epithelium. In the airways, the mucus lines the passages and traps any pathogens that may be in the air.
  • epithelium also contains ciliated cells. The cilia are tiny, hair-like organelles which can move. They move the mucus up to the top of the trachea, where is can enter the oesophagus and then can be swallowed and killed in the stomach (pH of the stomach is very low 1-2 so denatures the pathogen’s enzymes
46
Q

How does coughing and sneezing prevent pathogens from entering your body?

A

sudden expulsion of air will carry with it the microorganisms causing irritation

47
Q

What is inflammation?

A

swelling and redness of tissue caused by infection

48
Q

What is the process of inflammation?

A
  • mast cell in the body detects that a pathogen is present and release a substance called histamine.
  • histamine increases the leakiness of any capillaries that are nearby and this means that white blood cells can come out of the capillaries and into the infected tissues and mop up any pathogens
  • histamine also increases vasodilation and that increases the flow of blood so more white blood cells can get to the site of infection more quickly
  • as a result of blood plasma and white blood cells leaving the blood and entering the tissue fluid, there is an increased production of tissue fluid, which causes swelling (oedema).
49
Q

What are some other primary defences that humans have towards pathogens?

A
  • eyes are protected by antibodies and enzymes
  • ear canal is lined with wax, which traps pathogens
  • female reproductive system is protected by a mucus plug in the cervix and by maintaining relatively acidic conditions in the vagina
50
Q

What are secondary non-specific defences?

A

used to combat pathogens that have entered the body

51
Q

What are antigens?

A

chemical marker on a pathogens outer-membrane which can be recognised as foreign by the cell

52
Q

What are opsonins?

A
  • proteins that bind to the antigen and then allow phagocytes to bind
  • this is a type of antibody
53
Q

Outline phagocytosis which is carried out by neutrophils?

A
  1. neutrophil binds to the opsonin attached to the antigen of the pathogen
  2. the pathogen is engulfed by endocytosis forming a phagosome
  3. lysosome fuse to the phagosome and release hydrolytic enzymes into it
  4. after digestion, the harmless products can be absorbed into the cell
54
Q

What are macrophages and how is the way they carry out phagocytosis different from neutrophils?

A
  • type of phagocyte that is bigger than a neutrophil
  • travel in the blood as monocytes
  • play an important role in initiating the cells specific immune response.
  • when they engulf the pathogen, they do not fully digest it and the antigen from the surface of the pathogen is saved and moved to special protein complex on the surface of the cell. The cell becomes na antigen-presenting cell
55
Q

What are antigen-presenting cells?

A

a cell that isolates the antigen from a pathogen and places it on the plasma membrane so that it can be recognised by other cells in the immune system

56
Q

What is the specific immune response?

A

slower response compared to the non-sepecific response and is a complex series of events that leads to the production of antibodies that can combat the specific pathogen and memory cells that will provide long-term immunity.

57
Q

What are the two types of cells that are involved in the specific immune response?

A

-B lymphocytes (B cells) and T lymphocytes (T cells)

58
Q

What are the names of the 4 different type of T lymphocytes in the specific immune response?

A
  • T helper cells
  • T killer cells
  • T memory cells
  • T regulator cells
59
Q

What are the 2 different type of cells that the B lymphocytes (B cells) can develop into?

A
  • plasma cells

- B memory cells

60
Q

What happens at the first stage of the specific immune response (presentation of antigens)?

A
  • antgiens can be presented via macrophages
  • antigens can be presented on infected cells
  • antigens can be presented via pathogens in the tissue fluid
61
Q

What happens at the second stage of the specific immune response (activation-clonal selection)?

A
  • antigens shape is complimentary to both T killer cells and T-helper cells in the lymph node. Antigens shape is complimentary to B cells.
  • This is known as clonal selection.
62
Q

What happens at the third stage of the specific immune response (proliferation)?

A

-once the correct lymphocytes have been activated they must increase in numbers to become effective. This is achieved by mitotic cell division

63
Q

What happens at the fourth stage of the specific immune response (differentiation)?

A

-The B and T lymphocytes do not manufacture the antibodies directly. Once selected, clones of the lymphocytes develop into a range of useful cells

64
Q

What cells do T lymphocytes differentiate into?

A
  • T killer
  • T helper
  • T memory
  • T-regular cells
65
Q

What cells do B lymphocytes differentiate into?

A
  • Plasma cells which make antibodies

- B memory cells which remain in the blood

66
Q

What do T killer cells do?

A
  • attack infected host cells

- release. chemical called perforin onto the infected cell which perforates the membrane of the infected cell

67
Q

What do T memory cells do?

A

cells that remain in the blood for a long time, providing long-term immunity

68
Q

What do T helper cells do?

A

-stimulate B cells to divide which make antibodies, they do this by releasing a chemicals called cytokines

69
Q

What are T-regulator cells?

A

cells that are involved with inhibiting or ending the immune response

70
Q

What are interleukins?

A

signalling molecules that are used to communicate between different white blood cells

Biology A-Level -James (18 decks)

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