B4.3- Infection and response

Question 1

What are pathogens and how do they

make us ill?

Answer 1

Pathogens are microbes that make us ill.

They produce toxins.

Question 2

2. Give 3 ways in which communicable

diseases are spread

Answer 2

• Direct contact
• Air
• Water

Question 3

Suggest 3 ways in which communicable
diseases can be prevented. Explain your
answer for each.

Answer 3

• Mosquito nets
• Insecticides
• Cooking food thoroughly
• Using condoms
• Vaccination

Question 4

Name 2 viral diseases in humans and

describe the symptoms of each.

Answer 4

HIV: Causes flu-like symptoms at first and
leads to immune system damage. AIDS
occurs when infections and cancers can no
longer be dealt with.
Measles: Causes a red rash and fever.

Question 5

Name 2 bacterial diseases in humans and

describe the symptoms of each.

Answer 5

Salmonella: Causes fever, abdominal
cramps, diarrhoea and vomiting
Gonorrhoea: Thick yellow or green
discharge from the vagina or penis and pain
on urinating.

Question 6

What type of pathogen causes malaria

and how is it spread?

Answer 6

The pathogen for malaria is a protist.

Malaria is spread by a mosquito vector.

Question 7

What type of pathogen causes rose black

spot and describe its effects on plants.

Answer 7

Rose black spot is a fungal disease.
Purple or black spots develop on leaves.
They often turn yellow and drop.

Question 8

Describe 2 defense systems in humans

against pathogens entering the body.

Answer 8

• Mucus in airways trap microbes.
• Tiny hairs line the airways and move
the mucus away from the lungs.
• Acid in the stomach kill pathogens.
• Ear wax traps pathogens
• Scabs.

Question 9

Describe 3 ways in which white blood

cells defend against pathogens.

Answer 9

Lymphocytes produce antibodies.
Phagocytes engulf pathogens.
Antitoxins are produced.

Question 10

How do vaccines work?

Answer 10

Vaccines contain weakened pathogens.
The white blood cells produce specific
antibodies in response.
Memory cells remain in the body.
If the real pathogen enters the body our
white blood cells reproduce rapidly and
kill the pathogens.

Question 11

What do antibiotics do?

Give an example of an antibiotic.

Answer 11

Antibiotics like penicillin kill bacteria.

Question 12

What is the problem caused by using
too many antibiotics?
When should antibiotics not be used?

Answer 12

Overusing antibiotics can lead to
resistant bacteria that cannot be killed
by antibiotics.
Antibiotics should not be used for viral
infections or mild bacterial infections.

Question 13

Why is it difficult to develop drugs

that kill viruses?

Answer 13

Viruses get inside host cells and use
them to reproduce and it is hard to kill
them without damaging the host cell.

Question 14

Give 2 examples of drugs developed

from plants.

Answer 14

The heart drug digitalis originates from
foxgloves. The painkiller aspirin
originates from willow.

Question 15

Describe how new drugs are tested

and trialed.

Answer 15

New drugs are first tested in a lab for
toxicity.
They are then tested on animals.
Small groups of healthy volunteers are
used to test for side-effects.
Large groups of patients are then used
to check how effective the drug is and
what dosage should be used.
The whole process takes many years and
a large sample of people are tested to
make it more reliable.
Placebos are used to compare results
and the test is double-blind to avoid
bias.

Question 16

Describe how monoclonal antibodies are produced.

Answer 16

Stimulating mouse lymphocytes to make a particular
antibody.
The lymphocytes are combined with a tumour cell to make a cell called a hybridoma cell.
Single hybridoma cells are cloned to produce many identical cells that all produce the same antibody.
A large amount of the antibody can be collected and purified

Question 17

What is a hybridoma cell?

Answer 17

A hybridoma cell is a lymphocyte combined with a tumour cell.

Question 18

Give 4 ways in which monoclonal antibodies can be used.

Answer 18

Uses of monoclonal antibodies:

• diagnosis such as in pregnancy tests
• in laboratories to measure the levels of hormones
and other chemicals in blood, or to detect pathogens
• in research to locate or identify specific molecules in
a cell or tissue by binding to them with a fluorescent
dye.
• to treat some diseases e.g. cancer.

Question 19

Give one advantage and one disadvantage of using

monoclonal antibodies to treat cancer.

Answer 19

Advantage:
Monoclonal antibodies can be used to treat cancer.
The drug can be delivered to cancer cells without harming other body cells.
Disadvantage:
Monoclonal antibodies produce more side-effects than expected.

Question 20

Name 3 symptoms of plant diseases

Answer 20

• stunted growth
• spots on leaves
• areas of decay (rot)
• growths
• malformed stems or leaves
• discolouration
• the presence of pests.

Question 21

Name an insect that can cause plant disease

Answer 21

Aphids

Question 22

Name 2 minerals that can cause plant deficiency diseases.

Answer 22

Nitrate deficiency causes stunted growth

Magnesium deficiency causes chlorosis.

Question 23

Name 2 physical plant defence responses and 2 chemical plant defence responses.

Answer 23

Physical defence responses:
• Cellulose cell walls.
• Tough waxy cuticle on leaves.
• Layers of dead cells around stems (bark on trees)
Chemical plant defence responses:
• Antibacterial chemicals.
• Poisons to deter herbivores

Question 24

Name 2 mechanical adaptations of plants to prevent

infection.

Answer 24

Mechanical adaptations:
• Thorns and hairs deter animals.
• Leaves which droop or curl when touched.
• Mimicry to trick animals