Topic 3: Infection and Response

Question 1

What is a communicable disease?

Answer 1

A disease caused by a pathogen which can be passed between animals or plants eg. flu.

Question 2

What is a pathogen?

Answer 2

A disease-causing microorganism e.g. bacteria.

Question 3

How do bacteria cause disease?

Answer 3

Once inside the body, they divide rapidly by binary fission. They kill cells and produce harmful toxins.

Question 4

How do viruses cause disease?

Answer 4

They invade and reproduce inside living body cells, leading to cell damage.

Question 5

Give three ways in which pathogens can be spread

Answer 5

● By air - flu, tuberculosis and the common cold are spread by droplet infection.
● By water - fungal spores in water spread plant diseases.
● By direct contact - common in plant diseases and sexually transmitted infections.

Question 6

Give four ways in which the spread of pathogens can be reduced

Answer 6

● Hygiene - handwashing, disinfectants, tissues.
● Reducing contact with infected individuals - quarantine.
● Removing vectors - use of pesticides and insecticides, removal of habitats.
● Vaccination.

Question 7

What is salmonella?

Answer 7

A type of bacteria found in raw meat, poultry and eggs. If they enter the body via food poisoning, they can affect natural gut bacteria.

Question 8

What are the symptoms of salmonella food poisoning?

Answer 8

● Fever
● Abdominal cramping
● Vomiting
● Diarrhoea

May be fatal in very young or elderly populations due the risk of dehydration.

Question 9

How can the spread of salmonella be limited?

Answer 9

● Vaccinating animals intended for consumption
● Keep raw meat away from cooked meat
● Disinfect hands and surfaces after contact with raw meat
● Thoroughly cook meat

Question 10

What is gonorrhoea?

Answer 10

A sexually transmitted bacterial infection caused by unprotected sex with an infected individual. Early symptoms include yellow/green discharge from genitals and painful urination, although it may be symptomless.

Its spread can be controlled through the use of antibiotics (no longer penicillin as many strains are resistant) and using condoms.

Question 11

What is a vaccination?

Answer 11

Contains a dead or inactivated form of the pathogen which stimulates white blood cells to produce complementary antibodies to the pathogen. In the case of a second infection, memory cells can rapidly produce the correct antibodies and prevent illness.

Question 12

What is herd immunity?

Answer 12

If a sufficiently high proportion of a population are immune to a disease (especially through vaccination), the spread of this disease will be limited.

Question 13

What are the advantages of vaccinations?

Answer 13

● They have eradicated many deadly diseases eg. smallpox.
● Many epidemics can be prevented by vaccinations.
● Herd immunity protects those who cannot have vaccinations

Question 14

What are the disadvantages of vaccinations?

Answer 14

● Not guaranteed to work - might not protect against multiple strains of a pathogen.
● May be side effects or adverse reactions.

Question 15

What drugs are used to cure some bacterial diseases?

Answer 15

Antibiotics - they can kill bacterial pathogens inside the body.

Question 16

How do antibiotics work?

Answer 16

Antibiotics eg. penicillin kill bacterial pathogens inside the body, but do not kill human cells. Whilst some antibiotics kill a wide range of bacteria, it is important that the right antibiotic is used for specific bacteria.

Question 17

Why can antibiotics not be used to treat viral diseases?

Answer 17

Antibiotics have no effect on viral pathogens as they live inside the host’s (human) cells. Therefore, it is difficult to design drugs that would kill the virus and not destroy human cells at the same time.

Question 18

What is antibiotic resistance?

Answer 18

Antibiotic resistance occurs when mutations lead to individual bacteria being resistant to an antibiotic. These bacteria are able to survive, reproduce and pass on their alleles, leading to a greater proportion of antibiotic-resistant bacteria. This is concerning as some types of bacteria are becoming resistant to all known antibiotics, so the diseases that they cause cannot be cured.

Question 19

How can we prevent antibiotic resistance?

Answer 19

● Avoid overuse and unnecessary use of antibiotics - eg. antibiotics are often used for viral infections.
● Finish antibiotic courses - to ensure all bacteria is killed.

Question 20

What effect do painkillers have on infectious diseases?

Answer 20

Painkillers can only treat the symptoms but do not kill pathogens.

Question 21

What plant is the heart drug digitalis extracted from?

Answer 21

Foxgloves

Question 22

What painkiller originates from a compound found in willow bark?

Answer 22

Aspirin

Question 23

What antibiotic was discovered by Alexander Fleming from a type of mould?

Answer 23

Penicillin

Question 24

What are the four qualities of a good medicine?

Answer 24

● Effective
● Safe
● Stable
● Able to be taken in and removed easily

Question 25

What three main factors are tested for when developing new drugs?

Answer 25

● Toxicity
● Efficacy
● Dose

Question 26

How is preclinical testing carried out?

Answer 26

In a laboratory - uses cells, tissues and live animals

Question 27

How is clinical testing carried out?

Answer 27

Uses healthy volunteers and patients. Firstly, the drug is tested at a low dose on healthy people - then tested on patients and on a larger scale to find the optimum dose. Often, one group receive a placebo (not the test drug) and the other group receive the actual drug, in order to assess its efficacy.

Question 28

What is the difference between a single-blind and a double-blind trial?

Answer 28

In a single-blind trial, only the doctor knows whether the patient is receiving the drug or the placebo. In a double-blind trial, neither the patient nor the doctor knows. Double-blind trials help remove bias on the part of the doctor.

Question 29

What is a peer review?

Answer 29

Where the results of drug trials are checked over by scientists knowledgeable in this field.

Question 30

Give examples of physical defence responses used by plants

Answer 30

● Cellulose cell walls
● Tough waxy cuticle on leaves
● Outside layer on stems/bark on trees
● Leaf fall

Question 31

Give examples of chemical defence responses used by plants

Answer 31

● Antibacterial chemicals

● Poisons

Question 32

Give examples of mechanical defence responses used by plants

Answer 32

● Thorns and hairs to deter animals
● Leaves that droop/curl on contact
● Mimicry to trick animals