5.6 and 5.7

Question 1

passive immunity

Answer 1

produced by intro of antibodies from outside source and is acquired immediately

no direct contact with pathogen or its antigen is necessary

antibodies aren’t produced by individual, no memory cells are formed and the antibodies aren’t replaced after being broken down

Question 2

active immunity

Answer 2

produced by stimulating production of antibodies by persons own immune system

direct contact with pathogen and its antigen is necessary

Question 3

artificial active immunity

Answer 3

vaccination- immunisation

inducing immune response without suffering symptoms of disease

body produces own antibodies and memory cells

Question 4

natural active immunity

Answer 4

individual becomes infected with disease under normal circumstances

body produces own antibodies and memory cells

Question 5

vaccination

Answer 5

individual is injected with small amount inactive form of pathogen that contains one or more type of antigen

stimulates immune response against particular disease

memory cells are produced to allow long-lasting immunity

Question 6

5 factors of successful vaccine programme

Answer 6

1. economically available in sufficient quantities to immunise most of vulnerable popn
2. few side-effects
3. producing, storing and transporting vaccine must be available(technologically advanced equipment, hygienic conditions and refrigerated transport)
4. means of administering vaccine properly at appropriate time- training staff at different centres throughout popn
5. possible to vaccinate vast majority of vulnerable popn to produce herd immunity

Question 7

herd immunity

Answer 7

large proportion of popn has been vaccinated to make it hard for pathogen to spread

difficult for susceptible person to meet infected

protects vulnerable who can’t be vaccinated
- e.g. pregnant, babies, young children and those with compromised immune system

Question 8

6 reasons vaccines may not eliminate disease

Answer 8

1. fails to induce immunity in certain people e.g. defective immune systems
2. people may develop disease immediately after vaccination before immunity levels are high enough to prevent it(harbour and re-infect)
3. pathogen may mutate frequently so vaccines are ineffective as antigens are no longer recognised by immune system(antigenic variability)
4. many variables of particular pathogen so impossible to develop vaccine that is effective against them all
5. certain pathogen conceal themselves inside cells or in areas out of reach from immune system e.g. intestines
6. people may have objections to vaccination for religious, ethical or medical reasons

Question 9

6 ethics of vaccines

Answer 9

1. involves animals
2. side effects that sometimes cause long-term harm
3. who should undergo vaccine testing- unknown health risks
4. where should vaccine be trialled- popn where it is most common
5. should all of popn should be vaccinated - compulsory even if objections
6. should expensive vaccine treatments still go ahead when disease is almost eradicated

Question 10

HIV

Answer 10

human immunodeficinecy virus
causes acquired immune deficiency syndrome

Question 11

structure of HIV

Answer 11

outside has lipid envelope where peg-like attachment proteins are embedded

inside envelope is capsid protein layer
within are two single strands of RNA and some enzymes

enzyme reverse transcriptase catalyses production of DNA from RNA- so is a retrovirus

Question 12

replication of HIV

Answer 12

1. HIV enters bloodstream and circulates around body
2. protein on HIV readily binds to protein CD4, mostly on t helper cells
3. protein capsid fuses with cell helper csm. RNA and enzymes of HIV enter t helper cell
4. HIV reverse transcriptase converts virus’ RNA to DNA
5. new DNA is moved to T helper cell’s nucleus where it is inserted into cell’s DNA
6. HIV DNA in nucleus creates messenger RNA using cells enzymes. mRNA contains instructions for making new viral proteins and RNA to go into new HIV
7. mRNA passes out of nucleus through nuclear pore and uses cells protein synthesis mechanisms to make HIV particles
8. HIV particles break away from T helper cell with piece of its csm surrounding them which forms lipid envelope

Question 13

how HIV causes AIDS

Answer 13

kills or interferes with normal function of T helper cells

without sufficient number of T helper cells, immune system cannot stimulate b cells to produce antibodies or cytotoxic t cells that kill infected cells

body cannot produce adequate immune response so becomes more susceptible to other infections and cancers

Question 14

AIDS symptoms

Answer 14

infections of lungs, intestines, brains and eyes
weight loss
diarrhoea

Question 15

ELISA test

Answer 15

enzyme linked immunosorbent assay

uses antibodies to detect presence and quantity of protein in sample

Question 16

ELISA procedure

Answer 16

1. apply a sample to surface to which all of antigens will attach
2. wash surface several times to remove unattached antigens
3. add antibody that is specific to antigen that is being detected and leave two to bind
4. wash surface to remove excess antibody
5. add second antibody with an enzyme attached to bind to first
6. add colourless substrate of enzyme. the enzyme acts on substrate to change into coloured product
7. amount of antigen present is relative to intensity of colour that develops

Question 17

why antibiotic are ineffective against viral diseases

Answer 17

viruses rely on host cell to carry out metabolic activities so lack own metabolic pathway and cell structures so antibiotics cannot disrupt any of them

viruses have protein coat so don’t have sites where antibiotics can work

viruses are within organisms own cells so antibiotics can’t reach them

Question 18

how antibiotics work

Answer 18

antibiotics inhibit certain enzymes required for synthesis and assembly of peptide cross-linkages in bacterial cell walls(made of murein- a peptidoglycan)

the walls are weakened, making them unable to withstand pressure of osmosis so the cells burst and bacterium dies