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A Level Biology : Content > Topic 6B : Microorganisms & Immunity > Flashcards

Topic 6B : Microorganisms & Immunity Flashcards

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1
Q

bacteriocidal antibiotics

A

kill bacteria

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2
Q

bacteriostatic antibiotics

A

prevent bacteria growth

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3
Q

antibiotics

A

chemicals that kill or inhibit the growth of microorganisms

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4
Q

name two processes in a bacteria cell that antibiotics can inhibit

A

inhibit enzymes that make chemical bonds in bacterial cell walls which prevents bacteria from growing properly and can also lead to cell death as weakened cell cant take the pressure as water moves in by osmosis causing the cell to burst.

inhibits protein production by binding to bacterial ribosomes so enzymes cant be produced so metabolic processes needed for growth and development cant occur.

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5
Q

hospital acquired infections

A

infections caught while a patient is being treated in hospital

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6
Q

how are HAIs transmitted

A

staff/ visitors not washing their hands before and after visiting a patient

coughs and sneezes not being contained in a tissue

equipment and surfaces not being disinfected after use

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7
Q

codes of practice

A

staff/ visitors encouraged to wash their hands before and after visiting a patient

equipment and surfaces should be disinfected after use

people with infections should be moved to isolation ward so they are less likely to transmit the infection to other patients

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8
Q

codes of practice for infections caused by antibiotic-resistant bacteria

A

doctors shouldn’t prescribe antibiotics for minor bacterial infections or viral infections

doctors shouldn’t prescribe antibiotics to prevent infections

doctors should use narrow-spectrum antibiotics if possible

doctors should rotate the use of different antibiotics

patients should take all antibiotics prescribed so infections are fully cleared

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9
Q

what are the different routes pathogens can enter the body

A

cuts in skin

digestive system via contaminated food/drink

respiratory system by being inhaled

other mucosal surfaces eg inside of nose

vectors

formites

inhalation

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10
Q

stomach acid as a barrier to prevent infection

A

acidic conditions of the stomach kill the pathogens, however some survive and pass into the intestines where they can invade cells of the gut wall and cause disease.

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11
Q

skin as a barrier to prevent infection

A

skin is a physical barrier

if damaged, pathogens on the surface can enter the bloodstream.

blood clots at area of damage prevent pathogens from entering but some enter before a blood clot is formed.

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12
Q

gut and skin flora as a barrier to prevent infection

A

intestines and skin are naturally covered in billions of harmless microorganisms (flora) which compete with pathogens for nutrients and space which limits number of pathogens living in the gut and on the skin making it harder to infect the body.

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13
Q

lysozymes as a barrier to prevent infection

A

mucosal surfaces produce secretions that contain the enzyme lysozyme which kills bacteria by damaging their cell walls leading to them bursting.

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14
Q

what three mechanisms make up the non-specific immune response of the body

A

inflammation at site of infection

production of interferons

phagocytosis and lysozyme action

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15
Q

what are neutrophils

A

phagocytes

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16
Q

in what response are neutrophils involved

A

immediate

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17
Q

where are neutrophils made

A

bone marrow

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18
Q

where are neutrophils found

A

blood and tissue fluid

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19
Q

what are macrophages

A

phagocytes

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20
Q

where are macrophages made

A

bone marrow

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21
Q

in what response are macrophages involved

A

specific immune

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22
Q

are macrophages bigger than neutrophils

A

yes

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23
Q

where are neutrophils found

A

blood and develop in lymph nodes

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24
Q

inflammation

A

the site where a pathogen enter the body usually becomes red, warm, swollen and painful

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25
Q

explain the process of inflammation

A

damaged vessels release histamines which cause vasodilation increasing the blood flow to the site of infection allowing loads of immune system cells to reach the infected site.

the permeability of blood vessels is also increased allowing immune system cells to move out of the blood vessels into the infected tissue.

these immune cells then destroy the pathogen.

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26
Q

interferons

A

when cells are infected with viruses, these proteins are produced

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27
Q

role of interferons

A

prevent viruses spreading to uninfected cells by preventing them to attaching to host cells therefore they cant enter cells and cant replicate

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28
Q

list several ways interferons work

A

prevent viral replication by inhibiting production of viral proteins.

activate cells involved in specific immune response to kill infected cells.

activate other mechanisms of non specific immune response.

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29
Q

phagocytosis

A

the process of a phagocyte engulfing a pathogen

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30
Q

explain the process of phagocytosis and lysozyme action

A

a phagocyte recognises antigen on a pathogen and the cytoplasm of phagocyte moves around the pathogen and engulfs it via endocytosis.

pathogen is now contained in phagocytic vacuole in the cytoplasm of phagocyte.

a lysosome that contains digestive enzymes fuses with phagocytic vacuole and the enzymes break down the pathogen.

phagocyte presents the pathogen’s antigens to activate immune cells (antigen-presenting cell)

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31
Q

what is the name of the bacteria that causes tuberculosis

A

Mycobacterium tuberculosis

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32
Q

how is mycobacterium tuberculosis transmitted

A

through the inhalation of tiny droplets containing the bacteria when talking, sneezing or coughing.

drinking infected milk

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33
Q

how does mycobacterium tuberculosis causes disease

A

bacteria is taken up by a phagocyte in the lungs where they survive and replicate.

immune system seals off infected phagocytes in tubercles making the bacteria dormant so the person shows no symptoms hence why they don’t develop the disease straight away.

reactivation of dormant bacteria happens in people with weakened immune system.

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34
Q

state the sequence of symptoms of TB

A

initial symptoms include fever, general weakness and severe coughing cause by inflammation of lungs.

as the disease progresses it damages the lungs and if untreated it causes respiratory failure leading to death.

it can also spread to other parts of body.

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35
Q

what is HIV caused by

A

virus

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36
Q

what other symptoms does TB cause

A

weight loss

fever

loss of appetite

breathing problems

coughing

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37
Q

what factors increase the risk of TB transmission

A

poor health

poor diet

overcrowded living conditions

close contact

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38
Q

how can you prevent the transmission of TB

A

improve living standards

treat cattle diseases

protective clothing

good hygiene

ventilation

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39
Q

what features has the bacterium Mycobacterium Tuberculosis evolved to help them evade the immune system

A

when engulfed by phagocytes, they produce substances that prevent lysosome action so they are not broken down and can multiply undetected in phagocytes.

disrupts antigen presentation in infected cells, preventing the immune system from recognising and killing infected phagocytes.

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40
Q

how is HIV transmitted

A

through bodily fluids

bloodstream by sharing needles, blood transfusions cuts and grazes.

maternal transmission by breastfeeding

sexual transmission (unprotected sex)

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41
Q

how can HIV be prevented

A

use of condoms

clean needles

awareness programmes

avoiding promiscuity

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42
Q

how does HIV infect the body

A

attachment protein on the virus attaches to CD4 receptor on membrane of the host T helper cell.

capsid released into cell where it uncoats and releases the genetic material into cell cytoplasm.

reverse transcriptase used to make complementary strand of DNA from the viral RNA template.

double stranded DNA is made and inserted into human DNA.

host cell enzymes make viral proteins from viral DNA found within human DNA.

viral proteins assembled into nee viruses which bud from the cell and go on to infect other cells.

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43
Q

what features has HIV evolved to help them evade the immune system

A

protein coat constantly changes so immune system cant target and destroy.

it reduces the number of immune cells in the body.

has high rate of mutation in the genes coding for antigen proteins meaning that the structure of antigens constantly changes so memory cells wont recognise the new strains and the body has to produce primary response for each new strain

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44
Q

at what point will a patient show a HIV positive result

A

3-12 weeks after infection, when HIV antibodies appear in the blood

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45
Q

how can some people be immune to HIV

A

they lack the CD4 receptor on T helper cells

46
Q

why is it difficult to create vaccines for AIDS

A

virus mutates rapidly so antigens on viral surface continually change.

animal testing to develop vaccines not possible because HIV only infects humans.

virus hides itself for years inside macrophages so vaccine may not work properly.

47
Q

when are people with HIV classified as having AIDS

A

when symptoms of failing immune system appear

or

T helper cell count drops below a certain level

48
Q

opportunistic infections

A

when people with AIDS develop diseases/infections that wouldn’t cause serious problems in people with healthy immune system.

49
Q

the length of time between infection of HIV and development of AIDS

A

around 10 years without treatment

50
Q

state the sequence of symptoms of AIDS

A

initial symptoms include minor infections of mucous membrane and recurring respiratory infections caused by low number of T helper cells.

as AIDS progresses the number of T helper cells decreases and patients become more susceptible to more serious infections eg tuberculosis.

at late stages, patients have a very low number of T helper cells and suffer from range of serious infections such as toxoplasmosis of brain

51
Q

what factors affect the progression of HIV into AIDS

A

existing infections

strain of HIV

age

access to healthcare

52
Q

describe structure of bacteria

A

cell wall

slime capsule

plasmid

flagellum

pili

ribosomes

mesosomes

circular DNA

53
Q

slime capsule

A

protective slimy layer of polysaccharide which helps the cell to retain moisture and adhere to surfaces

protects bacteria from attack by cells of immune system

54
Q

pili

A

short hair-like structures that help bacteria stick to other cells and can be used in gene transfer.

55
Q

describe the structure of a virus

A

capsid

attachment proteins

envelope

reverse transcriptase

nucleic acid (DNA/RNA)

smaller than bacteria

56
Q

reverse transcriptase

A

protein inside capsid

57
Q

attachment proteins on virus

A

stick out from the edge of capsid or envelope allowing the virus to cling on to a suitable host cell.

58
Q

virus envelope

A

extra outer layer stolen from cell membrane of previous host cell

59
Q

pathogen

A

any organism that causes disease

60
Q

infectious disease

A

diseases caused by pathogens

61
Q

why are viruses referred to as particles instead of cells

A

acellular and non-living

cant self-reproduce

no metabolism

62
Q

retrovirus

A

viruses that contain RNA as their genetic infou

63
Q

where are b cells produced and mature

A

produced and mature in bone marrow

64
Q

in which response are B cells involved in

A

homoral

65
Q

B effector cells

A

differentiate to produce plasma cells which release antibodies

66
Q

B memory cells

A

remain in the body for months or years enabling an individual to respond quickly to the same antigen.

they are specific to the antigen encountered during the primary immune response.

67
Q

where are T cells produced and mature

A

produced in bone marrows and mature in the thymus gland

68
Q

in which response are T cells involved

A

both cell mediated and humoral

69
Q

T helper cells

A

activate phagocytes and B cells and aid T killer cells to divide

70
Q

T killer cells

A

destroy cells with foreign antigens on their surface by releasing perforin and cytotoxins

71
Q

T memory/effector cell

A

a long lived T cell that has receptors for an antigen due to its encounter with prior infection or vaccination

72
Q

what is APC

A

antigen presenting cell - displays foreign antigens with MHC on their surfaces for T cells to recognise.

73
Q

plasma cells

A

clones of B cells that secrete loads of antibody specific to the antigen into the blood.

74
Q

what are antibodies made of

A

four polypeptide chains (two heavy and two light) with each chain having a variable region and a constant region

disulfide bridges hold the polypeptide chains together

75
Q

antigen-antibody complex

A

variable region of antibody form the antigen binding site and the shape of each region is complementary to a particular antigen.

hinge regions allows flexibility when antibody binds to antigen.

constant region on antibody allow binding to receptors on immune system cells and its same in all antibodies

76
Q

agglutination of pathogens

A

each antibody has two binding sites so an antibody can bund to two pathogens at the same time so pathogens become clumped together.

phagocytes bind to antibodies and phagocytose a lot of pathogens all at once.

77
Q

neutralisation of toxins

A

antibodies can bind to the toxins produced by pathogens which prevents the toxins from affecting human cells so toxins are neutralised.

toxin-antibody complexes are also phagocytosed.

78
Q

preventing the pathogen binding to human cells

A

when antibodies bind go antigens on pathogens they may block cell surface receptors that pathogens need to bind to the host cell so pathogen cant attach and infect the host cells.

79
Q

what are the two forms of antibodies

A

membrane bound (attached to the membrane of a B cell) or secreted.

80
Q

how do membrane-bound and secreted antibodies differ

A

membrane-bound have an extra section of protein that anchors them to the B cell membrane

81
Q

introns

A

sections of genes that dont code for amino acids

82
Q

exons

A

sections of genes that code for amino acids

83
Q

pre-mRNA

A

during transcription, introns and exons are copied into mRNA so mRNA strands contain both introns and exons

84
Q

splicing

A

removal of introns

85
Q

post-transcriptional change

A

the removal of introns and exons being joined forming mRNA strands

86
Q

alternative splicing

A

exons as well as introns are removed to form different mRNA strands

87
Q

primary immune response

A

when pathogen enters the body for the first time the antigens on its surface activate the immune system.

non specific immune response activates first which activates the specific immune response

88
Q

why does primary response happen slowly

A

there aren’t many B cells that can make the antibody needed to bind to the antigen

89
Q

what happens when exposed to antigen during primary response

A

both T and B cells produce memory cells which remain in the body for a long time

T memory cells remember the specific antigen and will recognise it a second time round.

B cells record the specific antibodies needed to bind to the antigen.

90
Q

immune

A

the immune system of a person has the ability to respond quickly to a second infection.

91
Q

secondary response

A

when the same pathogen enters the body again, the immune system will produce quicker stronger immune response

92
Q

active immunity

A

you get when immune system makes its own antibodies after being stimulated by an antigen

93
Q

natural active immunity

A

you become immune after catching a disease

94
Q

artificial active immunity

A

become immune after been given vaccine containing a harmless dose of antigens

95
Q

passive immunity

A

you get from being given antibodies made by different organism so immune system doesn’t produce antibodies of its own.

96
Q

natural passive immunity

A

when baby becomes immune due to antibodies it received from its mother through placenta or breast milk.

97
Q

artificial passive immunity

A

you become immune after being injected with antibodies

98
Q

how do vaccines give you immunity without getting the disease

A

vaccines contain antigens that stimulate primary immune response against a particular pathogen without pathogen causing disease which results in body producing memory cells meaning you become immune without getting any symptoms

some vaccines contain many different antigens to protect against different strains of pathogens caused by antigenic variation

99
Q

evolutionary race

A

the struggle between pathogens and their hosts to outdo each other

100
Q

antigenic variation

A

HIV has a high rate of mutation in the genes that codes for antigen proteins. These mutations change the structure of antigens and it forms new strains of the virus

101
Q

what cell produces antibodies

A

b cells

102
Q

what are antigens made of

A

polysaccharides (proteins & sugars)

103
Q

what are the two types of cytokines

A

interferons

interleukins

104
Q

list the several ways interleukins work

A
105
Q

what are cytokines

A

molecules released by cells which trigger an immune response in the affected area by activating B cells and T killer cells

106
Q

cell mediated response

A

protects against intracellular infections

antigens are detected by receptors

no formation of antibodies

107
Q

humoral response

A

protects against extracellular infections

antibodies detect antigens

formation of antibodies

108
Q

immunological memory

A

when cloned B cells from humoral response produce memory cells

109
Q

clonal expansion

A

when same pathogens enters again and B memory cells divide rapidly to produce many plasma cells

110
Q

describe the role of antigen presentation in the body’s specific immune response to infection by viruses

A

macrophages present antigen to T helper cells

T helper cell needed to activate T killer or B cells

B cell acting as antigen presenting cell to itself

B cells differentiate into plasma cells and produce antibodies

infected cell presents antigen to T killer cell which destroys infected host cells

A Level Biology : Content (18 decks)

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