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AS BIOLOGY OCR > Communicable disease > Flashcards

Communicable disease Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are bacteria

A
  • prokaryotes
  • e.g. (animals) tuberculosis, bacterial meningitis
  • e.g. (plants) ring rot
  • damages cells directly and releases chemicals and toxins
  • can be classified by either basic shape or cell walls
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2
Q

What are viruses

A
  • non living infectious agents
  • e.g. (animals) HIV/AIDS, influenza
  • e.g. (plants) Tobacco Mosaic Virus
  • Enter host cells, use cells to replicate then burst to release replicated cells
  • 50x smaller in length than bacteria
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3
Q

What are protoctists

A
  • Parasitic, may need vector to transfer them to their hosts
  • E.g. (animals) malaria
  • E.g. (plants) late blight in potato/tomato
  • Enter host cell and feed on contents
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4
Q

What are fungi?

A
  • E.g. (animals) athletes foot, ring worm in cattle
  • E.g. (plants) black sigatoka
  • spreads over surface of cell as hyphae filaments
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5
Q

What are methods of direct transmission of disease in animals

A 
DIRECT CONTACT:
- kissing, direct skin to skin contact, faeces
INNOCULATION: 
-break in the skin
- animal bite
- sharing needles
INGESTION:
- Taking in contaminated food
- microorganisms in hands
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6
Q

What are methods of indirect transmission of disease in animals

A

DROPLET INFECTION:
- coughing or sneezing
VECTORS:
- transmitting pathogens from one host to another (not always animals
FOMITES:
- inanimate objects e.g. bedding, socks or cosmetics

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7
Q

Factors that affect transmission of disease in animals ?

A
  • overcrowding
  • poor nutrition
  • compromised immune system
  • poor disposal of waste
  • climate change
  • culture and infrastructure
  • socioeconomic factors
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8
Q

What are methods of direct transmission of disease in plants

A
  • Involves direct contact of a healthy plant with any part of a diseased plant
  • E.g. ring root, tobacco mosaic virus, tomato and potato blight and black sigatoka
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9
Q

What are methods of indirect transmission of disease in plants

A 
SOIL CONTAMINATION:
- infected plants leave pathogens or spors
VECTORS:
- wind
- water
- animals
- humans
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10
Q

Factors that affect transmission of disease in plants ?

A
  • Planting varieties of crops that are susceptible to disease
  • Over-crowding increases 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 spread of diseases; changing conditions allow animal vectors to spread to new areas; drier conditions may reduce spread of disease.
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11
Q

What are physical plant defences against pathogens?

A
  • Lignin = waterproof
  • Stomata closed when not required for gas exchange and may close if can sense unknown organism
  • Cellulose cell wall
  • Bark on trees
  • Waxy cuticle over leaf epidermis which reduce chances of plant pathogens gaining entry or spreading very far inside
  • Casparian strip in the endodermis of the root is impenetrable
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12
Q

What are active plant defences against pathogens?

A

• Hypersensitivity: the almost immediate death of tissues surrounding the site of infection by a pathogen is highly effective because many pathogens require living host cells to survive and spread.
• Cell signaling
• Produce high levels of callose which is deposited between the cell walls and cell membranes in cells next to infected cells.
o These callose papillae act as barriers, preventing the pathogens entering the plant cells around the site of infection.
o Callose also blocks sieve plates in phloem which seals of infected part preventing the spread of pathogens.
o Callose deposited in the plasmodesmata between infected cells and their neighbours, sealing them off from the healthy cells and helping to prevent the pathogen spreading
• Systemic acquired resistance
• Tylose swells up in xylem stopping pathogens moving and also contains toxic chemical to kill pathogens
• Production of phytoalexins (defense chemicals)
o Delay reproduction of pathogens
o Disrupt metabolism in the pathogen
o Stimulate the secretion of chitinases that break down the cell walls of the hyphae of fungal pathogens
o Disrupt the cell surface membrane of bacteria

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13
Q

What are chemical plant defences against pathogens?

A
  • Sticky resins in bark that prevent spread of pathogens
  • Receptor molecules on cell surface membranes that detect pathogens and activate plant defenses
  • Secretion of inhibitors of enzymes e.g. cellulose used by pathogens to break down cell walls to gain entry to cells
  • Secreting compounds to support growth of microorganisms that complete with pathogens
  • Secretion of compounds toxic to pathogens
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14
Q

What are some primary defences against pathogens in animals?

A
  • Skin
  • Tears and Urine –> lysozymes
  • Mucous membranes
  • Expulsive reflexes (sneezing, coughing, vomitting)
  • Blood clotting (thromboplastin and serotonin)
  • inflammatory response
  • fevers
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15
Q

Describe the process of phagocytosis

A

Phagocytes engulf and digest pathogens by phagocytosis

  1. Pathogens produce chemicals that attract phagocytes
  2. Phagocytes recognize non-human proteins on the pathogen. This is a response not 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.
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16
Q

What are macrophages?

A

combine antigens from pathogens with glycoproteins to form a major histocompatibility complex (MHC). Macrophage moves the MHC to the plasma membrane and embeds the pathogenic antigens on the surface to become an antigen-presenting cell which stimulates the specific immune response.

17
Q

What are opsonins and cytokines?

A
  • Opsonins: attach to pathogen antigens and acts as a ‘tag’ to make them more attractive to phagocytes
  • Cytokines: released by phagocytes and informs other phagocytes of the infection
18
Q

Describe what each type of T cell is and does?

A

T HELPER
• These have CD4 receptors on their cell-surface membranes, which bind to the surface antigens on APCs.
• They produce interleukins made by the T helper cell stimulate the activity of B cells, which increase antibody production, stimulate production of other types of T cells and attracts and stimulates
• Macrophages to ingest pathogens with antigen-antibody complex
T KILLER
• These destroy the pathogen carrying the antigen
• They produce a chemical called perforin, which kills the pathogen by making holes in the cell membrane so is freely permeable
T MEMORY
• Live for a long time and are a part of immunological memory.
• If they meet an antigen a 2nd time they divide rapidly to form a huge no. of clones of T killer cells that destroy the pathogen
T REGULATOR
• These cells surpress the immune system acting to control and regulate it.
• They stop the immune response once a pathogen has been eliminated, and make sure the body recognizes self-antigens and doesn’t set up an autoimmune response
• Interleukins are important in this control

19
Q

Describe what each type of B cell is and does?

A 
PLASMA CELLS
•	These produce antibodies to a particular antigen and release them into the circulation 
•	Live for a short time
B EFFECTOR CELLS
•	Divide to form plasma cell clones
B MEMORY CELLS
•	Live for a long time
•	Provide immunological memory
•	These are programmed to remember a specific antigen and enable the body to make a rapid response when a pathogen carrying an antigen is encountered again
20
Q

Describe the structure of antibodies and their action.

A

ANTIBODY STRUCTURE:
• Y shaped glycoproteins called immunoglobulins
• 2 pairs of polypeptide chains:
• 2 long heavy chains (H chains)
• 2 short light chains (L chains)
• All held together by sulfide bridges
ANTIBODY ACTION:
• Opsonins: binds to antigen. Antibody–antigen complex is easier to engulf for phagocytes
• Agglutination: clumps pathogens together for phagocytes to engulf many at a time
Antitoxin: Renders the pathogen’s toxins

21
Q

Whats an autoimmune disease, providing examples?

A

A disease in which the body’s immune system attacks healthy cells
E.G. Lupus –> Inflammatory disease that can affect any body part

22
Q

Whats natural active immunity?

A

Immune system produces T and B memory cells so if you meet a pathogen for a second time, your immune system recognizes antigens and can immediately destroy the pathogen before it causes disease symptoms – active natural immunity because body has itself acted to produce antibodies

23
Q

Whats natural passive immunity?

A

Some antibodies pass through the placenta from the mother to her baby so it has immunity to disease at birth and same with breast milk. This is natural passive immunity.

24
Q

Whats artificial passive immunity?

A

For certain potentially fatal diseases, antibodies are formed in one individual (often an animal), extracted then injected into the bloodstream of another individual. This gives temporary immunity

25
Q

Whats artificial active immunity?

A

The immune system of the body is stimulates to make its own antibodies to a safe form of an antigen (vaccine), which is injected into the bloodstream. The antigen isn’t usually the normal live pathogen as this could cause the disease and have fatal results

26
Q

Describe how vaccinations work?

A
  1. The pathogen is made safe in one of a number of ways so that the antigens are intact but there is no risk of infection. Vaccines may contain:
    a. Killed or inactivated bacteria or viruses (e.g.
    b. Attenuated (weakened) strains of live bacteria or viruses
    c. Toxin molecules that have been altered or detoxified
    d. Isolated antigens extracted from the pathogen
    e. Genetically engineered antigens
  2. Small amounts of the safe antigen (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
27
Q

Describe how epidemics are prevented

A
  • An epidemic is when a communicable diseases spreads rapidly to a population
  • A pandemic is when the same disease spreads rapidly across a world
  • At the beginning of an epidemic, mass vaccination can prevent the spread of the pathogen into a wider population
  • When vaccines are deployed to prevent epidemics, they often have to be changed regularly to remain effective
  • When a significant number of people In the population have been vaccinated, this gives protection to those who don’t have immunity, this is known as herd immunity, as there is minimal opportunity for an outbreak to occur

AS BIOLOGY OCR (6 decks)

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