Infection and Response

Question 1

What are the four types of pathogen?

Answer 1

Bacteria
Virus
Protist
Fungi

Question 2

How do viruses replicate?

Answer 2

Hijacking a cell’s replication machinery and making copies of itself

Question 3

How do viruses make us ill?

Answer 3

Invading and destroying our body cells

Question 4

How do bacteria replicate?

Answer 4

Binary fission

Question 5

How do bacteria make us ill?

Answer 5

By producing toxins

Question 6

How do you calculate bacterial growth?

Answer 6

Number of bacteria at the end = the number of bacteria at the start x 2to the power of number of divisions

Question 7

What are some examples of non-specific defence systems?

Answer 7

Skin, scabs, nose hair, mucus and stomach acid

Question 8

What are the three ways our immune system fights off pathogens?

Answer 8

Phagocytosis - when white blood cells engulf pathogens and digest them
Antitoxin production - white blood cells can produce antitoxins that neutralise the toxins that bacteria produce
Antibody production - white blood cells produce antibodies that fit to the antigens of specific pathogens

Question 9

How does a vaccine work?

Answer 9

By injecting a dead or weakened pathogen into the body to stimulate the lymphocytes to produce antibodies. If the same pathogen re-enters the body, the white blood cells respond quickly to produce the correct antibodies and prevents illness

Question 10

What is herd immunity?

Answer 10

When a large proportion of the population is immune to a disease, the spread of the pathogen in the population is reduced and eventually the disease may disappear e.g. smallpox

Question 11

What are the pros of vaccines?

Answer 11

Many diseases have been abolished because of them
Millions of lives have been saved
Minimal treatment

Question 12

What are the cons of vaccines?

Answer 12

Mild side effects can occur
Long term studies haven’t been completed

Question 13

How does antibiotic resistance happen?

Answer 13

In a population of bacteria a mutation occurs and one or more bacteria become resistant from the antibiotic
There is a reduced competition for resources so it thrives
Binary fission occurs with these mutated bacteria and the whole population is now resistant to the antibiotic

Question 14

What are drugs tested for during development?

Answer 14

Toxicity - safe to use
Efficacy - is it effective
Dosage - how much to give

Question 15

What is a placebo?

Answer 15

A substance that looks like a real drug but doesn’t actually affect the body

Question 16

What are the stages of drug development?

Answer 16

Pre-clinical testing: the drug is tested on tissues, cells or animals to test toxicity
The first stage of clinical trials: a small number of healthy volunteers are given the drug to ensure there are no negative side effects
The second stage of clinical trials: up to 400 patients are given the drug to test its efficacy and to find the optimal dose
The final stage of clinical trials: many patients take the drugs over and extended time to monitor any long term effects

Question 17

What are monoclonal antibodies?

Answer 17

Antibodies that have been produced from one cell that’s been cloned

Question 18

How are monoclonal antibodies produced?

Answer 18

Mouse lymphocytes are stimulated to make a particular antibody
The lymphocytes are combined with a tumour cell to make a hybridoma cell
This hybridoma cell can both divide rapidly and make the desired antibody
A large amount of the antibody can then be collected and purified - this is the monoclonal antibody

Question 19

What are the uses of monoclonal antibodies?

Answer 19

Cancer treatment
Pregnancy tests
Covid tests

Question 20

What are the physical defence adaptations of plants?

Answer 20

All plant cells have a cell wall which is difficult for organisms to penetrate
Leaves are covered with a thin oily layer called the waxy cuticle which is also difficult for organisms to penetrate and prevents the plant from attack
Bark is also a barrier for entry by microorganisms

Question 21

What are the chemical defence responses of plants?

Answer 21

Plants can release certain chemicals to protect themselves
For example antibacterial chemicals which prevent them from attacking the plant
They can also release poisons to deter herbivores from eating them

Question 22

What are the mechanical defence systems of plants?

Answer 22

Thorns / spines deter herbivores from eating the plant
Hairs on plants can irritate the mouths of herbivores trying to eat them
Some plants have leaves that can droop or curl when touched which can scare herbivores
Mimicry; this means that the plant appears to look like a different plant that has a defence mechanism e.g. the white dead nettle looks very similar to the stinging nettle so it won’t be approached