Topic 3 - Infection and Response

Question 1

How are infections caused?

Answer 1

Infections are caused whenever a foreign pathogen invades an organism.

Question 2

What are the four main types of pathogen?

Answer 2

Viruses, bacteria, fungi and protists.

Question 3

What is a virus?

Answer 3

A virus is a tiny, non-living particles that can reproduce rapidly within the body. They invade host cells and inserts its own DNA into the host cell’s DNA, which is copied and used to make new viruses. One the new viruses are made, they cause the cells to burst. The cell damage makes us feel ill.

Question 4

What are bacteria?

Answer 4

Bacteria are small living cells that either damage cells directly or by producing toxins. They reproduce rapidly in warm conditions and moist areas with a good supply of oxygen. The toxins released by bacteria can damage cells and tissues making us feel ill.

Question 5

What are fungi?

Answer 5

Fungi are single-celled organisms that have a body made up of hyphae (thread-like structures). The hyphae are able to grow and penetrate tissues, like human skin or surface of plants. The hyphae produce spores that can spread to other plants and animals.

Question 6

What are protists?

Answer 6

Protists are single-celled eukaryotic organisms. Many are parasites, meaning they live on or inside other organisms. They are often transferred to the host organism by a vector, such as an insect or mosquito. They make us feel ill by damaging our tissues.

Question 7

What are the three ways disease can be spread?

Answer 7

Air, direct contact and water.

Question 8

How can disease be spread through air?

Answer 8

Some pathogens are released into the air inside droplets when an organism sneezes or coughs. These droplets can be inhaled by other organisms.

Question 9

How can disease be spread through direct contact?

Answer 9

Some pathogens live on the surface of other organisms eg (the skin). If infected skin touches a surface, some of the pathogens can transfer from the skin to the surface. The pathogen then spreads to other people who also touch that surface.

Question 10

How can disease be spread through water?

Answer 10

Some pathogens contaminate water supplies. Organisms drinking this contaminated water can be infected by pathogens.

Question 11

How can disease spreading be prevented?

Answer 11

Vaccination, preventing contact with vectors, being hygienic and isolating yourself.

Question 12

How does vaccination prevent spread of disease?

Answer 12

Vaccination can make people immune to infection. The more people that are vaccinated, the less likely the disease is to spread.

Question 13

How does preventing contact with vectors prevent spread of disease?

Answer 13

If protist diseases are carried by vectors (organisms that carry pathogens without being infected), then using nets or pesticides can prevent contact with vectors.

Question 14

How does being hygienic prevent spread of disease?

Answer 14

Being hygienic, you can destroy pathogens or wash that away that they are not spread. You can also use antibacterial product to clean surfaces, along with sneezing into handkerchiefs to prevent spread of infection.

Question 15

How does isolation prevent spread of disease?

Answer 15

By being isolated to other people, contact with other organisms is prevent. This stops the infection from spreading.

Question 16

What are some examples of diseases caused by viruses?

Answer 16

Measles, HIV and TMV.

Question 17

What is measles?

Answer 17

Measles is a virus, that include red and rash skin along with a fever as symptoms. Young children are vaccinated against it, as it could be fatal. Spread by breathing in droplets from sneezes and coughs.

Question 18

What is HIV?

Answer 18

Human immunodeficiency virus (or HIV) is spread by sexual contact or exchange of body fluids (blood). HIV causes a flu-like illness. HIV enters the lymph nodes and attacks the body’s own immune cells, unless antiretroviral drugs are used properly. AIDS is caused by HIV, it happens when the infected person’s immune system has been badly damaged by HIV.

Question 19

What is TMV?

Answer 19

Tobacco mosaic virus (or TMV) is a pathogen that affect plants, like tobacco. The unique ‘mosaic’ pattern of the discolouration of the plant stunts the growth of the affected plant, because photosynthesis can’t take place.

Question 20

What are some examples of diseases caused by bacteria?

Answer 20

Salmonella and gonorrhoea.

Question 21

What is salmonella?

Answer 21

Salmonella happens when food has not been cooked properly or the food has been made in unhygienic conditions, which might lead to the ingestion (eating) of salmonella particles

Question 22

What are non-specific defences?

Answer 22

They are designed to prevent any pathogens from entering the body and causing harm.

Question 23

What are our non-specific defences?

Answer 23

Tears, mucus, stomach acid and skin.

Question 24

How do tears defend our body?

Answer 24

Tears contain enzymes that destroy any pathogens that make contact with our eye.

Question 25

How does mucus defend our body?

Answer 25

Mucus is produced in the respiratory system and traps the particles and bacteria entering our airways.

Question 26

How does stomach acid defend our body?

Answer 26

Glands in the stomach wall produce hydrochloric acid, which destroys any pathogens that enter the stomach.

Question 27

How does our skin defend the body?

Answer 27

Skin is a waterproof barrier that pathogens cannot pass through. Good bacteria live permanently on our skin, covering the surface and prevent pathogens from growing on our skin.

Question 28

What are the different functions of white blood cells?

Answer 28

Producing antibodies, antitoxins and the process of phagocytosis.

Question 29

Why do white blood cells produce antibodies?

Answer 29

White blood cells recognise foreign antigens (proteins) on the surface of pathogens and produce protein molecules called antibodies.

Question 30

Why are antitoxins produced?

Answer 30

Some bacteria produce toxins that can damage cells and tissues. The immune system responds to this by producing antitoxins, which neutralise the toxins released by the bacteria and prevent them from causing harm.

Question 31

What is phagocytosis?

Answer 31

A white blood cells finds the pathogen and engulfs it by changing shape. The white blood cell ingests (absorbs) and digests the pathogen, destroying it.

Question 32

How do antibodies work?

Answer 32

The white blood cells find antigens on the surface of cells. White blood cells recognise the foreign antigens on the surface of pathogens and produce protein molecules called antibodies. Antibodies have a complementary shape to the antigen and lock onto the pathogen, effectively ‘tagging’ them. This causes the micro-organisms to cluster, allowing other white blood cells to come and ingest them.

Question 33

What is the process of vaccination?

Answer 33

A dead or inactive form of a pathogen is injected into the blood. White blood cells recognise the foreign antigens and produce antibodies against them. Some white blood cells remain in the blood as memory cells. If the same pathogen invades the body again, the cells are able to produce antibodies faster and produce more antibodies, meaning that the antibody concentration remains in the blood for longer. Next time the same pathogen infects the vaccinated person, it will be destroyed by the immune system before illness is caused.

Question 34

What is herd immunity?

Answer 34

If a large percentage of the population is immune to a disease, it will make it very hard for a pathogen to spread.

Question 35

What are antibiotics?

Answer 35

Antibiotics are drugs developed to cure infections caused by bacteria.

Question 36

How do some antibiotics work?

Answer 36

They destroy the cell wall of the bacteria so that they can’t replicate.

Question 37

Why don’t antibiotics affect viruses?

Answer 37

They do not destroy viruses because viruses stay inside host cells and are not living cells.

Question 38

How are antibiotics specific?

Answer 38

Specific antibiotics are prescribed by medical doctors for specific diseases. The use of antibiotics has greatly reduced the number of deaths from infectious bacterial diseases.

Question 39

How have antibiotics benefitted the number of deaths?

Answer 39

The use of antibiotics has greatly reduced the number of deaths from infectious bacterial diseases.

Question 40

What is antibiotic resistance?

Answer 40

Some strains of bacteria are resistant to certain antibiotics. This means that these antibiotics cannot kill them.

Question 41

How can antibiotic resistance be stopped?

Answer 41

Doctors should only prescribe antibiotics if they are needed and not for minor infections or viral infections. Patients should complete their course of antibiotics to make sure that all bacteria are killed.

Question 42

What is MRSA?

Answer 42

MRSA is often called a ‘superbug’ as it is resistant to many antibiotics.

Question 43

What can happen if some bacteria mutate against antibiotics?

Answer 43

Some bacteria will have random mutations (change in DNA) in a population of bacteria. The mutated bacteria are resistant to antibiotics, so they can survive against it, whilst the non-resistant bacteria die. The resistant bacteria can reproduce rapidly because their competition has been destroyed by the antibiotics. When the resistant bacteria reproduce, they produce genetically-identical copies. These copies will all be resistant to the antibiotics.

Question 44

How were drugs extracted from the past?

Answer 44

They were extracted from plants and micro-organisms.

Question 45

Where does the heart drug digitalis originate from?

Answer 45

Digitalis originates from foxgloves which is a plant.

Question 46

Where does the painkiller aspirin originate from?

Answer 46

Aspirin originates from willow trees.

Question 47

Where is the antibiotic penicillin made from and who discovered it?

Answer 47

Alexander Fleming discovered penicillin, which is made from the penicillium mould.

Question 48

How are drugs made now?`

Answer 48

Drugs are synthesised (made) by chemists in the pharmaceutical industry, and the ingredients of these drugs may be chemicals extracted from plants.

Question 49

What are the different types of drugs being developed today?

Answer 49

Antiviral drugs, antibiotics and painkillers.

Question 50

What are antiviral drugs?

Answer 50

As viruses are found inside cells, it’s hard to destroy them without damaging the body’s cells and tissues. We use antiviral drugs to treat these viral infections.

Question 51

Why are antibiotics still being developed as of now?

Answer 51

Scientists are always trialling new antibiotics for when new strains of resistant bacteria appear.

Question 52

What are painkillers?

Answer 52

Painkillers are used to relieve the pain caused by an infection. They do not cure diseases or kill pathogens, but they do relieve the symptoms.

Question 53

Why do drugs have to be tested and trialled?

Answer 53

To check if the drug is safe (not toxic or harmful), how much of it is needed and if it works (efficient).

Question 54

What is the first stage of testing drugs?

Answer 54

Preclinical testing - scientists carry out early stage testing on human cells and tissues grown in the laboratory. This is also done on live animals. Testing on animals is useful to work out how toxic a drug is to cells. In the UK, new medicines have to undergo tests on two different live mammals. Many drugs fail at this stage if they damage cells or do not work.

Question 55

What is the second stage of testing drugs?

Answer 55

Clinical testing - clinical trials test drugs on healthy volunteers and patients to check that they are safe. They usually use low doses of the drug. If a drug is found to be safe at low doses, there are more clinical trials to work out the optimum (best) dose for the drug.

Question 56

What is a double-blind trial?

Answer 56

During clinical trials, some patients are given a placebo (an alternative that does not contain any of the drug). Whether a patient gets the drug or the placebo is randomly chosen. Neither the patient nor the doctor knows who has received which.

Question 57

What are the two main features of a double-blind trial?

Answer 57

Unbiased - these trials make sure it’s a fair test. If the patient or doctor knew what they were taking, the outcomes of the trial could be different.
Identical conditions - all the conditions are kept identical across the two groups so that only the drug has an impact on a patient’s health.