Infection And Response

Question 1

Pathogens

Answer 1

Microorganisms that enter the body and cause disease

Cause communicable diseases in both plants and animals

Bacteria, Viruses, Protists or Fungi

Question 2

Bacteria

Answer 2

Very small cells (1/100th size of body cells)

Reproduce rapidly inside the body

Make you feel ill by producing toxins that damage the cells and tissues

Question 3

Viruses

Answer 3

Not cells, much smaller, (1/100th size of bacterium)

Reproduce rapidly inside the body like bacteria

Live inside the cells and replicate themselves using the cells’ machinery to produce many copies of themselves

Cell then bursts releasing all new viruses

Cell damage makes you feel ill

Question 4

Protists

Answer 4

Eukaryotes
Most single-celled

Some are parasites which live on or inside other organisms and cause damage

Often transferred to organisms by a vector, which doesn’t get the disease itself

Question 5

Fungi

Answer 5

Some are single-celled

Others have body made up of hyphae (thread-like structures)

Hyphae can grow and penetrate human skin and surface of plants, causing disease

Hyphae can produce spores, which can be spread to other plants and animals

Question 6

How can pathogens be spreads?

Answer 6

WATER - pathogens can be picked up by drinking or bathing in dirty water e.g cholera- bacterial - spread by drinking water contaminated with diarrhoea of other sufferers

AIR - pathogens can be carried in air and can be breathed in e.g. influenza - virus - caused by airborne pathogens in droplets when someone coughs or sneezes

DIRECT CONTACT - pathogens can be picked up by touching contaminated surfaces, including skin e.g. athlete’s foot - fungus - skin itchy flakes off

Question 7

Measles

Answer 7

VIRUS

Spread by droplets from infected person’s sneeze or cough

Red skin rash and signs of a fever

Very serious/even fatal if complications

Most people vaccinated against it when young

Question 8

HIV

Answer 8

VIRUS

Spread by sexual contact or exchanging bodily fluids such as blood

Flu-like symptoms for a few weeks

Virus attacks immune cells

No symptoms for several years - antiretroviral drugs taken during this time

Question 9

Tobacco Mosaic Virus (TMV)

Answer 9

VIRUS

Affects many species of plants like tomatoes

Causes mosaic pattern on leaves - parts of leaves become discoloured

Discolouration means plant can’t carry out photosynthesis well, so virus affects growth

Question 10

Rose Black Spot

Answer 10

FUNGAL

Causes purple/black spots to develop on leaves of rose plant - leaves turn yellow and drop off

Stops photosynthesis from happening so plant doesn’t grow very well

Spreads through environment or by wind

Using fungicides and stripping plant of affected leaves which are then destroyed so fungus can’t spread

Question 11

Malaria

Answer 11

PROTIST

Part of protist’s life cycle takes place inside mosquito

Mosquitos are vectors

Every time mosquito feeds on another animal, it infects it by inserting protist intro animal’s blood vessels

Malaria cause repeating episodes of fever and can be fatal

People can be protected from mosquitoes using insecticides and mosquito nets

Question 12

Salmonella

Answer 12

BACTERIAL

Type of bacteria causing food poisoning

Suffer from fever, stomach cramps, vomiting and diarrhoea

Symptoms caused by toxins bacteria produce

Eating food that’s been contaminated with bacteria e.g. chicken caught suedes whilst alive, or eating food prepared in unhygienic conditions

Question 13

Gonorrhoea

Answer 13

BACTERIAL

Sexually transmitted disease (STD)

Caused by bacteria

Pain when urinating, thick yellow or green discharge from vagina or penis

Antibiotics used and so should barrier methods of contraception e.g. condoms

Question 14

How can the spread of disease be reduced or prevented?

Answer 14

Being hygienic

Destroying vectors

Isolating infected individuals

Vaccination

Question 15

Body’s defence system

Answer 15

Skin acts as barrier to pathogens - also secretes antimicrobial substances which kill them

Hair and mucus in nose trap particles that could contain pathogens

Trachea and bronchi secrete mucus to trap pathogens - also lined with cilia which waft mucus up to the back of the throats where it can be swallowed

Stomach produces hydrochloric acid that kills pathogens which make out far from the mouth

Question 16

Three lines of attack from white blood cells

Answer 16

1) Consume
2) Produce antibodies
3) Produce antitoxins

Question 17

1) Consuming them

Answer 17

WBCs can engulf foreign cells and digest them - phagocytosis

Question 18

2) Producing Antibodies

Answer 18

Every invading pathogen has unique molecules called antigens on its surface

When some types of WBC come across a foreign antigen they will produce proteins called antibodies with lock onto the invading cells so that they can be found and destroyed by other WBCs
The antibodies produced are specific to that type of antigen

Antibodies are then produced rapidly and carried around body to find similar bacteria or viruses

If the person is infected with the same pathogen again, the WBCs will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won’t get ill

Question 19

Producing antitoxins

Answer 19

These counteract toxins produced by the invading bacteria

Question 20

Vaccination

Answer 20

Involves injecting small amounts of dead or inactive pathogens

These carry antigens which cause the body to produce antibodies or attack them - even though the pathogen is harmless

If the live pathogen of the same type appear after that, the white blood cells can rapidly mass-produce antibodies to kill off the pathogen

Question 21

Pros of Vaccination

Answer 21

Vaccines have helped control lots of communicable diseases that were once common in the UK e.g. polio, measles, whooping cough, rubella, mumps, tetanus

Big outbreaks of disease (epidemics) can be prevented if a large population is vaccinated. That way, even people who aren’t vaccinated are unlikely to catch the disease because fewer people able to pas it on

Question 22

Cons of Vaccination

Answer 22

Vaccines don’t always work - sometimes don’t give immunity

Can sometimes have a bad reaction to a vaccine e.g. swelling or s maybe something more serious like a fever or seizures. Bad reactions are very rare