Topic 3 - Infection And Response

Question 1

Viruses

Answer 1

Not cells
1/100th the size of bacterium
Live inside cells and replicate using cells machinery to produce copies of themselves. Cells then burst releasing new viruses

Question 2

Bacteria

Answer 2

Very small cells
1/100th size of body cells
Make you feel ill by producing toxins that damage cells and tissues

Question 3

Protists

Answer 3

Single celled eukaryotes
Some protists are parasites - live on or inside other organisms and cause them damage
Often transferred by a vector

Question 4

Fungi

Answer 4

Some fungi are single celled
Others have a body made up of hyphae (thread like structures)
Hyphae can grow and penetrate human skin and surface of plants - causing diseases
Hyphae can produce spores - can spread to other plants and animals

Question 5

How pathogens can be spread

Answer 5

Water - drinking or bathing dirty water. Cholera is a bacterial infection spread by drinking water contaminated with diarrhoea of people infected
Air - Airborne pathogens carried in the air in droplets produced when you cough or sneeze. Influenza virus causes flu spread this way
Direct Contact - Touching contaminated surfaces. Athlete’s foot is a fungus spread by touching same things as infected person

Question 6

Measles

Answer 6

Measles - a virus
Spread - droplets from infected person’s sneeze or cough
Develop - red skin rash, signs of a fever
Measles can lead to pneumonia (lung infection) and encephalitis (brain infection)
Most are vaccinated when young

Question 7

HIV

Answer 7

HIV - virus
Spread - sexual contact, exchanging of bodily fluids such as blood. Can happen when people share needles when taking drugs
Causes flu like symptoms for a few weeks. Doesn’t then experience symptoms for several years
HIV can be controlled with antiretroviral drugs - stops virus replicating
Virus attacks immune cells
If immune system badly damaged - can’t cope with other infections or cancers - late stage HIV infection or AIDS

Question 8

Tobacco mosaic virus TMV

Answer 8

TMV a virus
Affects many species of plants, e.g. tomatoes
Causes a mosaic pattern on leaves of plants - parts become discoloured
Discolouration means plant can’t carry out photosynthesis - affects growth

Question 9

Rose Black Spot

Answer 9

Rose Black Spot a fungus
Causes purple or black spots to develop on leaves of rose plants
Leaves can turn yellow and drop off
Less photosynthesis can happen so doesn’t grow well
Spreads in water or by the wind
Can treat by using fungicides and getting rid of affected leaves
Affected leaves destroyed so doesn’t spread to other rose plants

Question 10

Malaria

Answer 10

Malaria is caused by a protist
Transferred by mosquitoes - mosquitoes are vectors
They pick up malaria protist when they feed on infected animal
Everytime they feed on another animal transfer protist to animals blood
Causes repeating episodes of fever
Spread can be stopped by stopping mosquitoes from breeding
People protected by using insecticides and mosquito nets

Question 11

Salmonella

Answer 11

A bacteria
Causes food poisoning,fever,stomach cramps,vomiting,diarrhoea
Caused by toxins bacteria produces
Can get salmonella by eating: chicken that caught disease when it was alive, contaminated food prepared in unhygienic conditions
In UK most poultry is given a vaccination

Question 12

Gonorrhoea

Answer 12

A bacterial disease - sexually transmitted disease
Get pain when urinate - thick yellow or green discharge from vagina or penis
Originally treated with antibiotic - penicillin
Some strains have become resistant to it
To prevent spread - antibiotics, barrier methods of contraception

Question 13

How to reduce or prevent spread of disease

Answer 13

Hygienic - washing hands can stop infecting another person
Destroying vectors - killing organism that spreads disease stops disease being passed
Isolating infected individuals - prevents someone passing it on
Vaccination - can’t develop and pass on

Question 14

Defence system of the body

Answer 14

Skin - barrier to pathogens, secretes antimicrobial substances that kill pathogens
Hairs and mucus in nose trap particles that could contain pathogens
Trachea and bronchi - secrete mucus to trap pathogens, lined with cilia that waft mucus up to back of throat where it can be swallowed
Stomach - produces hydrochloric acid - kills pathogens

Question 15

White blood cells

Answer 15

Engulf foreign cells and digest them - phagocytosis

Invading pathogens has unique antigens on its surface
When B lymphocytes detect a foreign antigen produce proteins called antibodies. Antibodies specific to that antigen. Allows pathogen to be found by other white blood cells

Produce antitoxins that counteract toxins produced by invading bacteria

Question 16

Vaccinations

Answer 16

Injecting small amounts of dead or inactive pathogens
They carry antigens that makes your body produce antibodies

MMR vaccine - measles, mumps, rubella

Question 17

Pros and Cons of Vaccination

Answer 17

Pros - Helped control once common communicable diseases in UK - Smallpox, polio, mumps, rubella
Epidemics of a disease can be prevented if large percentage of population vaccinated - herd immunity - unvaccinated people unlikely to catch as less people to pass it on

Cons - Sometimes have bad reaction to a vaccine - rare

Question 18

Bacteria becoming resistant to antibiotics

Answer 18

Bacteria can mutate to become resistant to an antibiotic
To slow down rate of development of resistant strains important to not over prescribe antibiotics otherwise not get antibiotics for less serious infections

Question 19

Drugs that come from a plant

Answer 19

Aspirin - painkiller and to lower fever. Developed from chemical found in willow
Digitalis - treat heart conditions. Developed from chemical in foxgloves

Question 20

Penicillin

Answer 20

Alexander Fleming clearing out Petri dishes containing bacteria. One of the dishes had mould on it - area around mould free of bacteria
The mould producing antibiotic substance

Question 21

Stages in drug testing

Answer 21

1) Tested on human cells and tissues
Can’t use cells and tissues that affect whole/multiple body system

2) Testing on live animals
To test efficacy (whether the drug works and produces the effect you’re looking for)
Find its toxicity and best dosage (concentration that should be given)
Some think testing on animals is cruel / safest way to make drug safe before giving to humans

3) Clinical trials
4) Results published after peer review - prevents false claims

Question 22

Clinical trials

Answer 22

1) Tested on healthy volunteers - make sure no harmful side effects when body working normally. Low dose initially increases over time
2) Drugs tested on people suffering with illness and optimum dose is found
3) Patients put randomly into 2 groups
One group given drug the other placebo
So doctor can see actual difference - allows for placebo effect (when patient expects treatment to work so feels better)
Clinical trials blind - patient doesn’t know which one they are getting
Double blind - neither patient or doctor knows, so doctors not subconsciously influenced by knowledge

Question 23

Monoclonal antibodies

Answer 23

Produced from clones of a single white blood cell

All antibodies created are identical and target only 1 specific protein antigen

Question 24

How to create monoclonal antibodies

Answer 24

Inject mouse with chosen antigen
Mouses B-lymphocytes create antibodies for the antigen
Take B-lymphocyte from mouse and fuse with a tumour cell to create a cell called a hybridoma
The hybridoma divides quickly and the clones all produce the same antibodies - monoclonal antibodies
Useful because they only bind to that specific antigen - to target specific cell or chemical in the body

Question 25

Monoclonal antibodies used in pregnancy tests

Answer 25

Hormone called HCG in urine of women only when pregnant
Bit of stick you wee on has some antibodies to hormone with blue beads attached
Test strip has more antibodies to the hormone stuck onto it
If pregnant - hormone binds to antibodies on blue beads, urine moves up stick carrying hormone and beads, bind to antibodies on strip, blue beads get stuck onto strip - turning blue
Not pregnant - urine moves up stick with blue beads but nothing to stick onto the test strip - doesn’t go blue