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Disease Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Pathogen

A

A microorganism that causes disease

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2
Q

How do bacteria cause disease?

A

Once in host cell, they can multiply rapidly. Presence causes disease by damaging cells or releasing toxins.
In plants, bacteria often live in vascular tissues causing them to blacken.

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3
Q

How do fungi cause disease?

A

Fungus lives in the skin of an animal and its hyphae, which forms a mycelium, grows under skin surface. Fungus can send out reproductive hyphae which grow to skin surface and release spores.
In plants fungus lives in vascular tissue to gain nutrients. Hyphae release extracelullar enzymes to digest surrounding tissue.

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4
Q

How do viruses cause disease?

A

Viruses invade cells and take over genetic machinery and other organelles. They cause the genetic machinery to make more copies of the virus and the host cell will burst to release many viruses that will infect healthy cells.

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5
Q

How do protoctista cause disease?

A

Enter host cell and feed on the contents as they grow

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6
Q

Diseases caused by bacteria

A

Tuberculosis
Bacterial meningitis
Ring rot (plants)

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7
Q

Diseases caused by viruses

A

HIV
Influenza
Tobacco mosaic virus

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8
Q

Disease caused by fungi

A

Black sigatoka ( bananas)
Blight (tomatoes and potatoes)
Ringworm (cattle)
Athlete’s foot

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9
Q

Diseases caused by protoctista

A

Malaria

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10
Q

Means of transmission of pathogenic organisms

A

Direct physical contact such as touching an infected person or surface
Faecal-oral transmission - eating/drinking contaminated food/water
Droplet infection - pathogen is carried inn droplets in the air
Transmission by spores

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11
Q

How to prevent transmission

A

Hygiene - wash hands regularly, sterilising surgical instruments
washing food, careful preparation of food
using and disposing of tissues, covering mouth to sneeze
use masks

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12
Q

Social factors that affect transmission

A 
Overcrowding
Poor ventilation
Poor health
Poor diet
Homelessness
Being around people who have migrated from a place where a disease is more common
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13
Q

Transmission of malaria

A

An uninfected person is bitten by a female Anopheles mosquito
Plasmodium migrates to the liver
Plasmodium migrates to blood
The person has malaria and gametes of plasmodium are in their blood
A female Anopheles mosquito sucks the blood and plasmodium develops and migrates to the mosquitos salivary gland
Another person is bitten

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14
Q

Physical plant defences against pathogens

A

Cellulose cell wall - acts as physical barrier and contain chemical defences that can be activated
Lignin thickening of cell walls - waterproof and almost completely indigestible
Waxy cuticles - prevent water collecting on the surface and pathogens can’t survive without water
Bark - contains a variety of chemical defences
Stomatal closure - when pathogens are detected, guard cells will close the stomata
Callose - a large polysaccharide that is deposited in the sieve tubes and blocks the flow in the sieve tube. This prevents spread of pathogen around the plant
Tylose formation - a swelling that fills the xylem vessels so that the vessel can no longer carry water. This prevents the spread of the pathogen. Tylose contains chemicals that are toxic to pathogens.

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15
Q

Active plant defences

A

Cell walls become thickened and strengthened with extra cellulose
Deposition of callose to strengthen cell wall and block plasmodesmata
Oxidative bursts that produce highly oxidative molecules capable of damaging cells of invading organisms
Increase in the production of chemicals

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16
Q

Plant chemicals against pathogens

A

Terpenoids - antibacterial and antifungal properties, may also create scent
Phenols - antibiotic and antifungal properties. Tannins in bark inhibit attack by insects
Alkaloids - nitrogen containing compounds give a bitter taste to inhibit herbivores feeding. They also inhibit or activate enzymes. Some inhibit protein synthesis
Defensive proteins - cysteine rich and have antimicrobial activity. Act on plasma membranes inhibiting ion channels
Hydrolytic enzymes - break down chitin in fungal cell walls, hydrolyse glycosidic bonds in glucans and degrade bacterial cell walls.

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17
Q

Necrosis

A

Deliberate cell death. By killing cells surrounding infection, pathogens have limited access to water and nutrients so prevent it spreading around the plant

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18
Q

Canker

A

A sunken necrotic lesion in the woody tissue, causes death of the cambium tissue.

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19
Q

Primary defences against disease

A 
The skin
Blood clotting and skin repair
Mucous membranes
Coughing and sneezing
Inflammation
Eyes protected by tears
Wax in ear canal
20
Q

How does the skin act as a primary defence?

A

The outer layer of skin (the epidermis) consists of keritinocytes which are produced by mitosis at the base of the epidermis. The cells migrate to the surface and dry out and the cytoplasm is replaced by keratin. By the time the cells reach the surface, they are dead and act as an effective barrier to pathogens.

21
Q

How does blood clotting act as a primary defence?

A

Involves calcium ions and at least 12 clotting factors many of which are released from platelets of the damaged tissue. The factors activate an enzyme cascade. Once a clot forms, it drys out to form a scab which shrinks as it dries, drawing the sides together. This makes a temporary seal as the kin repairs.
The first stage is the deposition of fribrous collagen under the scab. Stem cells in the epidermis divide by mitosis and these cells migrate to surface to form new skin. New blood vessels grow to supply oxygen and nutrients. Tissues contract to draw edges of cut together.

22
Q

How do mucous membranes act as a primary defence against disease?

A

Mucus is secreted from goblet cells which are in the epithelial layer. In airway, mucus lines passages and traps pathogens in the air. Ciliated cells waft the mucus along to the top of the trachea where it is swallowed down the oesophagus and killed by the stomach acid

23
Q

How does coughing and sneezing act as a primary defence against disease?

A

Areas prone to attack are sensitive and respond to irritation caused by microorganisms by coughing, sneezing or vomiting. The sudden expulsion of air will carry the microorganism with it.

24
Q

How does inflammation act as a primary defence against disease?

A

The presence of microorganisms is detected by mast cells which release histamine, a cell signalling substance. Histamine causes vasodilation and makes capillary walls more permeable to white blood cells and some proteins. Blood plasma and phagocytes leave blood and enter tissue fluid leading to increased production of tissue fluid causing swelling.

25
Q

Antigen presenting cell

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.

When a macrophage engulfs a pathogen, it does not fully digest it. The antigen is saved and moved to a special protein complex on the surface of the cell. The protein complex ensures the antigen presenting cell is not mistaken for a foreign cell

26
Q

Cytokines

A

Hormone-like molecules used in cell signalling to stimulate the immune response

27
Q

Opsonins

A

A type of antibody. They are protein molecules that bind to the antigen on the pathogen and allow phagocytes to bind.

28
Q

The steps of neutrophil attack

A
  1. Neutrophil binds to the opsonin attached to the antigen of the pathogen
  2. Pathogen is engulfed by endocytosis forming a phagosome
  3. Lysosomes fuse to the phagosome and release lytic enzymes into it
  4. After digestion, harmless products are absorbed into the cell
29
Q

Specialisations of a phagocyte

A
  • receptors on plasma membrane to bind to opsonin or a specific antigen
  • lobed nucleus allows cell to squeeze through narrow gaps
  • well developed cytoskeleton helps cell to change shape to engulf pathogen and to move lysosomes and vacuoles around the cell
  • many lysosomes containing lysin
  • many mitochondria for energy
  • many ribosomes to synthesise enzymes
30
Q

T helper cells

A

Release cytokines that stimulate B cells to develop and stimulate phagocytosis by the phagocytes

31
Q

T killer cells

A

Attack and kill host body cells that are infected by the pathogen and show the foreign antigen

32
Q

T memory cells

A

Provide long term immunity

33
Q

T regulator cells

A

Shut down the immune response after the pathogen has been successfully removed. They are involved in preventing autoimmunity.

34
Q

Plasma cells

A

Circulate in the blood, manufacturing antibodies

35
Q

B memory cells

A

Remain in body for years and act as immunological memory

36
Q

Examples of communication using cytokines

A
  • Macrophages release monokines which attract neutrophils by chemotaxis. Thos is the movement of cells towards a particular chemical. Others stimulate B cells to differentiate and release antibodies
  • T cells and macrophages release interleukins which can stmulate clonal expansion
  • Many cells can release interferon which inhibits virus replication and stimulates the activity of T killer cells
37
Q

The specific immune response

A
  1. Infection and reproduction of pathogen
  2. Presentation of antigens
  3. Clonal selection
  4. Clonal expansion (proliferation) - once the correct lymphocytes have been activated they must increase in numbers achieved by mitotic division
  5. Differentiation into T killer, T memory, T helper, plasma and B memory cells
38
Q

Agglutinins

A

As antibodies have two binding sites, they can bind to two antigens. When many antibodies do this they clump together pathogens. This means the agglutinated pathogens are unable to carry out some functions and they can be readily engulfed by phagocytes.

39
Q

Anti toxins

A

Some antibodies bind to molecules that are released by pathogenic cells. Anti toxins render toxic molecules harmless.

40
Q

Herd Vaccination

A

Using a vaccine to provide immunity to all or almost all of the population at risk.

41
Q

Ring vaccination

A

Used when a new case of a disease is reported. It involves vaccinating all the people in the immediate vicinity of the new case.

42
Q

Active immunity

A

Where the immune system is activated and manufactures its own antibodies

43
Q

Passive immunity

A

Immunity achieved when antibodies are passed to the individual through breast feeding or injection

44
Q

Artificial immunity

A

Immunity that is achieved as as result of medical intervention

45
Q

Natural immunity

A

Immunity achieved through normal life processes

Biology (16 decks)

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