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Biology > Immunity > Flashcards

Immunity Flashcards

1
Q

Describe the process by which vaccines provide immunity

A
  • contain dead or attenuated pathogens
  • MACROPHAGE presents antigen on surface
  • specific T cells with complementary receptors bind
  • stimulate B cells with complementary antibody on surface to divide by mitosis
  • differentiate into plasma cells which produce LARGE AMOUNTS OF antibodies
  • plus memory cells are produced
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2
Q

Difference between active and passive immunity

A

Active
- production of antibodies by plasma cells
- slow acting since it takes time to produce antibodies
- long lasting as memory cells produced
Passive
- antibodies are received from outside source
- fast acting
- short term since antibodies are broken down

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3
Q

Organelles involved in production of viruses

A
  • mitochondria to release energy

- ribosomes to synthesise proteins

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4
Q

Describe how an antibody works

A
  • binding sites are complementary in shape to antigens
  • hinges allow arms to spread to allow attachment of antigens at different distances
  • cause pathogen to agglutinate by joining together so it is easier for phagocytes to engulf
  • neutralise by binding to pathogen and prevent them from reaching and harming cells
  • act as markers to stimulate phagocytes
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5
Q

Why are viruses unaffected by antibiotics

A
  • lack a cell wall for them to interfere with

- cannot pass cell membrane to reach them inside cells

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6
Q

Antibiotic effect on bacteria

A

Inhibit enzymes required for synthesis of normal cell walls so bacteria killed from cell lysis (from osmosis)

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7
Q

Antigen

A
  • FOREIGN protein

- triggers an immune response by lymphocytes / production of ANTIBODY

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8
Q

Why do some vaccines have booster injections

A
  • immunological memory decreases overtime
  • more antigens so more memory cells produced
  • large amount of antibodies are produced rapidly if person was to become reinfected
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9
Q

How do pathogens cause disease

A
  • produce toxins

- damage/kill cells

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10
Q

Reasons for decrease in vaccinations

A
  • more people aware of harmful side effects / risks
  • fewer cases of disease
  • insufficient vaccine available/ too expensive to distribute
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11
Q

Herd Immunity

A
  • most people are vaccinated so disease cannot spread

- unvaccinated people less likely to contact infected people

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12
Q

Describe and explain curve for primary immune response

A
  • slow increase in antibody concentration as it takes time for phagocytes to stimulate T cells and produce plasma cells by clonal expansion to make antibodies
  • plasma cells die reducing antibody production
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13
Q

Describe and explain curve for secondary immune response

A
  • rapid increase in antibody concentration as memory cells differentiate into plasma cells and produce antibodies
  • start with memory cells so a larger amount of antibodies produced
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14
Q

Function of cytotoxic T cells

A
  • secrete cytotoxic chemicals called perforins
  • create pores in plasma membrane of infected cells
  • cytotoxins enter and destroy pathogen
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15
Q

Phagocytosis

A
  • phagocyte identifies pathogen as a foreign body by antigen
  • pathogen engulfed by phagocyte and enclosed in vesicles called phagosome
  • lysosomes fuse with wall of phagosome and release lysozymes which hydrolyse the cell wall of pathogen and destroy it
  • antigens presented on surface
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16
Q

Pathogen

A

Microorganism that causes disease

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17
Q

Examples of foreign antigens

A

Pathogens
Organ transplants
Toxins
Abnormal body cells (cancer)

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18
Q

Clonal Selection

A

Only lymphocytes specific to a certain antigen are activated

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19
Q

Describe advantage of memory cells

A
  • identify original antigen
  • divide rapidly in response to future infection
  • produce large quantity of antibodies at a faster rate
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20
Q

Antibody

A
  • protein specific to antigen

- secreted by plasma cells

21
Q

Describe structure of antibody

A

Made of four polypeptide chains

  • two heavy and two light
  • joined by disulphide bridges
22
Q

Monoclonal antibodies

A

Antibodies produced by a single clone of cells

23
Q

Describe humoral response

A
  • complementary ANTIBODY on B cell attaches to foreign antigen
  • antigen engulfed and processed by B cell
  • B cell presents antigen on its surface
  • T cells with complementary receptors attach activating clonal expansion
  • Memory cells and plasma cells produced
24
Q

Uses and advantages of monoclonal antibodies

A

Attached to cancer drugs
- target cells so cheaper since smaller doses needed
- non toxic and few side effects
Medical diagnosis

25
Q

Reasons vaccination may not eliminate disease

A
  • antigen variability
  • many strains of pathogen
  • pathogens hide from immune system so fail to induce immunity
  • unable to achieve herd immunity as people object on religious, medical and ethical grounds
26
Q

ELISA test

A
  • apply sample to a surface to which all antigens in sample will attach
  • wash sample to remove any unattached antigens
  • add antibody specific to antigen being detected for and leave to bind
  • wash to remove any unattached antibodies
  • add second antibody with enzyme attached which binds to first antibody
  • add colourless substrate so enzyme acts on it to cause colour change
  • intensity of colour is relative to amount of antigen present
27
Q

Structure of HIV

A

Lipid envelope
Attachment proteins
Capsid containing RNA
Reverse transcriptase catalyses production of DNA from RNA

28
Q

Describe how HIV works

A
  • binds to specific protein on T helper cells
  • protein capsid fuses with cell-surface membrane
  • RNA and enzymes enter T helper cell
  • reverse transcriptase converts viral RNA to DNA
  • HIV DNA transcribed into mRNA which is translated by ribosomes to form new HIV viruses
  • new HIV break away from T helper cell by budding (cell-surface membrane forms their lipid envelope)
29
Q

How does HIV create symptoms

A
  • kills T helper cells by replicating inside them
  • no T cells to stimulate B cells to produce antibodies
  • no cytotoxic T cells to destroy infected cells
  • body succumbs to opportunities infections
30
Q

Suggest what is meant by an attenuated pathogen

A
  • modified
  • by heat / chemical treatment
  • reduced reproduction rate
30
Q

Suggest reasons why an attenuated pathogen is better to use in a vaccine compared to a dead pathogen

A
  • more closely resembles real infection

- dead pathogen may have modified antigens

30
Q

Give reasons why doctors should not over prescribe antibiotics

A
  • constant exposure favours selection of resistant strains of bacteria formed by genetic mutations
  • reduces effectiveness of antibiotics / puts patients at risk
  • expensive
30
Q

Give reasons why it is important to finish a course of antibiotics

A
  • surviving bacteria could develop resistance
  • surviving bacteria could cause reinfection
  • some antibiotics inhibit growth of bacteria for body’s own immune response so might not allow sufficient time
31
Q

Explain differences between antibiotic reaching infected tissue by intravenous injection and by mouth

A

Intravenous injection
- provides high concentrations of antibiotic
- travels through capillaries to infected tissue directly
- not long lasting
Tablet by mouth
- lower concentrations since diluted by gut contents
- digested before entering blood stream so slower acting
- long lasting

32
Q

Explain how malarial parasite avoids immune response

A
  • infects red blood cells
  • reproduces inside liver cells
  • antigens are hidden / changes antigenic groups
33
Q

Suggest when passive immunity is necessary

A
  • short term protection
  • pathogen divides / spreads rapidly
  • body could succumb to infection before body produces immune response
34
Q

Describe how monoclonal antibodies are produced on a large scale

A
  • mouse infected with pathogen containing foreign antigen
  • B cells specific to antigen produced and extracted from spleen
  • tumour harvested from culture and fused with B cells
  • hybridoma cells are screened for antibody production and cultured
  • antibodies are extracted from culture
35
Q

Why does influenza virus require annual vaccinations but other infections do not

A
  • high rate of mutation
  • mutation changes antigens
  • antibodies do not recognise new antigens so new memory cells must be produced
36
Q

Suggest why blood group O is a universal donor despite containing antibodies A and B

A
  • will not cause agglutination

- greatly diluted over large blood volume

37
Q

Which part of the antibody is the variable position

A

top section including binding site

38
Q

Suggest why clonal expansion occurs

A
  • sufficient lymphocytes to destroy/disable pathogen

- all genetically identical so have receptors which are recognise antigen

39
Q

What is the difference between humoral and cell-mediated immune response

A
  • humoral involves antigens and pathogens that have not entered cells
  • humoral involves detection by antibodies on B cell
  • cell-mediated involves cells invaded by pathogens (or macrophages), transplant and tumour cells
40
Q

Suggest why B cells are fused with cancer cells in manufacture of antibodies

A
  • B cells have a limited life span and will eventually die

- fusing them with cancer cells = immortal so can be cultured

42
Q

Suggest why a logarithmic scale is used

A
  • allows a large range of values to be displayed
  • without small values being compressed at bottom of graph
  • so small values can be meaningfully interpreted
  • straight line graph
45
Q

Outline how binding of antigen to antibody on plasma membrane of B cell leads to raised antibody levels

A
  • B cell engulfs antigen and presents antigen on its surface
  • antigen recognised by specific T cell
  • stimulates B cells to divide by mitosis
  • form genetically identical cells
  • B cells differentiate into plasma cells to produce antibodies
46
Q

Explain why antibodies only affect specific foreign cells/pathogens

A
  • antibodies have a specific tertiary structure
  • complementary in shape to antigen
  • antigens ONLY found on specific cell
  • bind to antigen to form complex
47
Q

Difference between primary and secondary defence and what is phagocytosis considered

A
  • primary refers to mucus/ciliates epithelium/skin/stomach acid
  • secondary phagocytosis
48
Q

Suggest ways in which plants can protect themselves against infection by pathogens

A
  • produce callous
  • leaf drop or plant tissue death to prevent spread
  • produce toxic chemical to kill pathogen

Biology (14 decks)

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