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HL Bio > 6.3 defence against infectious diseases > Flashcards

6.3 defence against infectious diseases Flashcards

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Biology 101 flashcards
1
Q

skin and mucous membranes are _____ and serve as the _____ line of defence

A

surface barriers, first

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2
Q

how does skin serve as primary defence against disease-causing pathogens? (4)

A
  • protects external structures
  • epidermis is made out of dead skin cells -> form an impermeable layer
  • sebaceous glands secrete chemicals and enzymes -> inhibit microbial growth
  • secrets lactic acid and fatty acids -> lower pH
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3
Q

how do mucuous membranes serve as primary defence against disease-causing pathogens? (4)

A
  • protects internal structures e.g. trachea, oesophagus
  • consists of a thin region of living cells -> release fluids to wash away pathogens
  • secretes lysozomes -> destroy cell walls of pathogens
  • epithelial cells secrete mucous -> traps pathogens -> mucous containing pathogens are swept away for disposal by cilia
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4
Q

how does blood clotting protect the body?

A
  • prevents blood loss
  • prevents entry of pathogens into the bloodstream
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5
Q

outline how blood clots are formed when there is a cut (5)

A
  1. coagulation cascade occurs -> stimulated by clotting factors released by damaged cells and platelets
  2. clotting factors cause platelets to become sticky -> adhere to damaged region -> form a solid plug
  3. clotting factors trigger the conversion of prothrombin -> thrombin
  4. thrombin catalyses the conversion of soluble fibrinogen -> insoluble fibrin
  5. fibrin strands form a mesh around platelet plug -> traps blood cells -> form a temporary clot
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6
Q

what is the formation of a blood clot in the coronary arteries?

A

coronary thrombosis

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7
Q

how do blood clots form in coronary arteries? (7)

A
  1. when vessels are damaged -> cholesterol deposited
  2. atheromas develop in arteries which can calcify over time -> reducing the diameter of the lumen
  3. restricted blood flow -> incr. pressure -> damage of arterial wall
  4. damaged region is repaired w fibrous tissue -> significantly reduces elasticity of vessel wall
  5. smooth lining progressively degraded -> atherosclerotic plaques form
  6. if plaque ruptures -> blood clotting triggered, forming a thrombus -> restricts blood flow
  7. if the thrombus is dislodged it can cause blockage in smaller arterioles
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8
Q

why are blood clots dangerous?

A

occlusion of a coronary artery by a blood clot may cause a heart attack

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9
Q

what are the two key properties of the innate immune system?

A
  • non-specific
  • non-adaptive
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10
Q

how do phagocytes give rise to non-specific immunity? (6)

A
  1. phagocytic leukocytes move into body tissue in response to infection
  2. damaged tissues release chemicals -> draw white blood cells to the site of infection
  3. pathogens are engulfed by pseudopodia which surrounds the pathogen and then fuses -> forms an internal vesicle
  4. lysosome fuses with vesicle -> pathogen digested
  5. antigens presented on the surface of phagocyte -> stimulate third line of defence
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11
Q

what are two characteristics of the adaptive immune system?

A
  • specific, targets a response specific to pathogen
  • immunological memory, responds rapidly to re-exposure of pathogen
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12
Q

how are antibodies produced? (4)

A
  • when phagocytic leukocytes engulf a pathogen -> some present antigens on e surface (dendritic cell)
  • these cells migrate to the lymph node -> activate specific helper T lymphocytes
  • helper T cells release cytokines, activating particular B cell to be capable of producing antibodies specific to antigen
  • activated B cell divides and differentiates -> form plasma cells -> produce high amounts of antibodies
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13
Q

how do B cells contribute to long lasting immunity?

A

a small proportion of activated B cell will develop into memory cells

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14
Q

what are antigens? (short defin.)

A

a substance that the body recognises as foreign and that will elicit an immune response

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15
Q

what are antibodies? (short defin.)

A

a protein produced by B lymphocytes that is specific to a given antigen

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16
Q

what do antibodies do to help the immune system? (5)

A
  • target specific antigen on pathogen -> enhances capacity of immune system to recognise + destroy pathogen
    • neutralises pathogens -> bind to antigens present on pathogens -> prevent them from infecting host cells
    • one antibody can bind to two pathogens -> large scale agglutination can occur
    • precipitates dissolved antigens like toxins + foreign molecules
  • activate the complement system -> increases rate of phagocytosis of the pathogens
17
Q

how do antibiotics function? (short ans)

A

they kill or inhibit the growth of microbes by targeting prokaryotic metabolism

18
Q

why are antibiotics ineffective in killing viruses? (short ans)

A

viruses do not possess metabolism and instead take over the machinery of infected host cells

19
Q

name 2 cell parts antibiotics target

A
  • components of cell walls
  • 70s ribosomes
20
Q

how does penicillin function as an antibiotic? (2)

A
  • are competitive inhibitors of an enzyme needed to form the cell walls of many types of bacteria
  • cell walls are needed to maintain structural stability of the cell membrane -> damage to cell membrane -> bacteria death
21
Q

how does streptomycin function as an antibiotic? (3)

A
  • binds to 16s rRNA found in 70s ribosomes in prokaryotes
  • binding to ribosomes interfere w binding of tRNA to ribosomes -> resulting in errors in e translation process in protein synthesis
  • affects entire metabolic process -> death of bacteria
22
Q

why are some bacteria resistant to antibiotics? (4)

A
  • bacteria may evolve with genes that confer resistance to antibiotics
  • eg. beta lactamase gene -> produces beta lactamase which breaks down beta lactam group of antibiotics
  • resistant strains of bacteria proliferate very quickly after initial mutation
  • resistant strains can pass resistance genes to susceptible strains by bacterial conjugation
23
Q

why are there increasing antibiotic-resistant bacterial strains? (2)

A

over-prescription, misuse

24
Q

how was penicillin discovered? (short ans)

A
  • a plate containing S. aureus was contaiminated with penicillium mold culture
  • a halo was found around the mold -> showing that bacterial were killed by the extracellular secretions of the mold
25
Q

how did the florey and chain experiment show that penicillin can be medically applied?

A
  • florey tested penicillin on infected mice
  • eight were injected with streptococcus bacteria
  • four were injected with penicillin
  • untreated mice died of bacterial infection while the treated mice survived
  • demonstrated antibiotic potential as it killed bacterial and not human cells
26
Q

what are the effects of HIV? (5)

A
  1. HIV specifically targets the helper T lymphocytes which regulate the adaptive immune system
  2. following infection, virus undergoes a period of latency -> allows infected T lym to reproduce
  3. virus becomes active + begins to spread -> destroying T lym
  4. depletion of functional T lym -> antibodies cannot be produced -> immune system is weakened -> cannot effectively mount immune response against opportunistic infections
  5. body becomes susceptible to opportunistic infections -> death if body cannot defend itself
27
Q

how is HIV transmitted? (short ans)

A
  • unprotected sex
  • blood transfusion

HL Bio (53 decks)

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