Infection and response

Question 1

What is a pathogen?

Answer 1

it is a mircroorganism which passes a communicable disease from one organism to another.

Question 2

What are the different types of pathogens?

Answer 2

1. Viruses strand of RNA or DNA coated in a protein eg Covid 19
2. Bacteria prokaryotic eg salmonella
3. Fungi eukaryotic eg athletes foot
4. Protists - eukaryotic eg maleria

Question 3

Describe the life cycle of a pathogen

Answer 3

1. They infect a host
2. They reproduce/replicate quickly inside the host
3. They spread from the host to another host.

Question 4

What is an infectious pathogen

Answer 4

One that is easily passed from one host to another eg measles virus

Question 5

Describe different ways that pathogens pass between hosts

Answer 5

1. Airborne such as covid which is spread in tiny water droplets when an infected person sneezes.
2. Through dirty water eg cholera bacterium
3. Direct physical contact- sexual or non sexual eg chlamydia,
4. Through contaminated food, often reheated or not fully cooked eg salmonella
5. Passed by an animal, called a vector eg Malaria vi mosquitos

Question 6

Give some examples of viral diseases

Answer 6

1. Measles-
2. HIV/AIDS
3. Tobacco mosaic virus

Question 7

Describe infection by the measles virus

Answer 7

Measles- a highly infectious airborne virus the disease usually transmitted in water droplets via sneezing. Can cause serious medical complications including sterility and death. Children in the UK are immunised against measles but it used to cause thousands of deaths and permanent disabilities such as deafness in childhood.

Question 8

Describe infection by HIV

Answer 8

HIV stands for human immunodeficiency virus. It is transmitted when body fluids are shared, usually during sex or sharing needles by drug users. Ater months or even years the virus attacks the lymph nodes and destroys immunity cells. The host now has aquired immunity deficiency syndrome AIDS. They find it difficult to fight off diseases and often die from infections such as pneumonia & tuberculosis as well as cancers.
Prevention is through information on safe sex and needle sharing.

Question 9

Describe infection by Tobacco mosaic virus

Answer 9

This virus affects not only the tobacco plant but other related species such as tomatoes. The virus enters and damages the chloroplasts in parts of the leaf turning them yellow and giving them a mosaic like appearance. It is usually spread on tools, clothing or the hands of farm workers but can be spread by insects or by plants touching in the wind.
Farmer use a number of measure to try to prevent it
. using virus resistant strains
. removing infected plants as soon as they see the virus to stop the spread
.removing weeds around plants to stop the virus spreading

Question 10

Name some bacterial diseases

Answer 10

1. Salmonella

2. Gonorrhoea

Question 11

Describe infection by gonorrhoea

Answer 11

It is a sexually transmitted bacterial disease causing burning when urinating and a thick yellow/green discharge. Prevention includes use of condoms to stop the bacteria passing from person to person. Some strains of gonorrhoea are becoming resistant to antibiotics making treatment difficult.

Question 12

Describe infection by salmonella

Answer 12

Salmonella bacteria occurs in food and is spread by poor food hygiene practices and cooking incorrectly. It causes vomiting, fever abdominal cramps and diarrhoea. Mixing raw and cooked food in fridges and not cooking food thoroughly are two causes of infection in food.
Prevention includes vaccinating chickens against it and using good food hygiene measures.

Question 13

Describe infection by rose black spot

Answer 13

Caused by a fungus it infects the leaves of the plant causing black spots reducing photosythesis and growth. The leaves often go yellow and fall off. The spores of the fungus travel on the wind or by rain splash. It is treated using fungicides or by removing and burning infected leaves.

Question 14

What is a protist?

Answer 14

A pathogen which is always unicellular or multicellular without tissues. They infect both plants and animals the most common one being the plasmodium protists which cause malaria

Question 15

Describe infection by malaria

Answer 15

Caused by plasmodium protists which are transmitted from host to host by mosquitos. They suck the blood of an infected organism, then pass the plasmodium in their saliva when they suck the blood of the all the rest of the organisms they bite.
Mosquitos breed in stagnant water so draining ponds and marshy areas destroys their breeding areas.
Using insect repellents and mosquito nets to help avoid getting bitten is the other preventative measure. There is no vaccine for malaria

Question 16

Describe the ‘first line of defence’ non specific barriers to infection

Answer 16

1. skin- covers the body to protect from pathogens
2. Anti microbial secretions such as tears
3. Hairs and cilia which are covered in mucus and act as a barrier
4. Stomach acid, the hydrochloric acid in the stomach is strong enough to kill many pathogens in the digestive system

Question 17

What are the 2nd line of defence against infection blood cells called

Answer 17

1 Phagocytes

2. Lymphocytes

Question 18

What is an antibody?

Answer 18

A protein which is a match to a specific antigen found on a pathogen.

Question 19

What is an antigen?

Answer 19

It is a protein on a pathogen which the body recognises as dangerous and foreign.

Question 20

Describe how lymphocytes help prevent infection

Answer 20

1. They are a type of white blood cell
2. They recognise the antigens on pathogens.
3. They then produce large numbers of antibodies to match the antigens
4. The antibodies fit on to the antigen which helps clump the pathogens together and stop them spreading around the body.
5. Special memory lymphocytes remember the antigens and produces antibodies very quickly if we get infected by the same pathogen again making it more unlikely to make a person ill again.

Question 21

What are phagocytes?

Answer 21

1. They are a type of white blood cell
2. They engulf pathogens and dead cells.
3. They are attracted to areas of infection.
4. They bind to pathogens
5. Their membrane surrounds the pathogen engulfing them into a vacuole inside it.
6. Enzymes inside the vacuole break down the pathogen
7. The process is called phagocytosis.

Question 22

What is a vaccine?

Answer 22

It is a small quantity of a dead pathogen or genetically modified material. It has the same antigens as the pathogen you are being vaccinated against. Lymphocytes produce antibodies and antitoxins. Memory lymphocytes remember the shape of the antigens so that if you become infected with the real pathogen your body can produce antibodies very quickly and prevent illness.

Question 23

What is a booster vaccination

Answer 23

It is a 2nd vaccination, usually after a number of years to help refresh the memory lymphocytes.

Question 24

What is an antibiotic?

Answer 24

A medicine which kills bacteria, they have no effect on viruses. Some antibiotics weaken the cell wall of the bacteria making them burst! Others stop them from reproducing or alter the bacterial enzymes.

Question 25

Describe the discovery of penicillin

Answer 25

Sir Alexander Fleming discovered penicillin in 1928. the penicillin fungus landed on an open petri dish and stopped the bacteria from multiplying. He realised that the fungus was producing chemicals which killed the bacteria and went on to refine it into the drug penicillin.

Question 26

What is antibiotic resistance?

Answer 26

Many different antibiotics have been developed over the last century. Some pathogens have been evolving which are resistant to antibiotics, these make it difficult to treat them which is very concerning for doctors. Drug companies are working hard to find new antibiotics that these pathogens are not resistant to.

Question 27

What is a painkiller?

Answer 27

A drug which treats the symptoms of an illness but doesn’t kill the pathogens causing it.

Question 28

What is a double blind drug trial

Answer 28

One which neither the patients or the doctors running the trial know which is the real drug and which is the placebo

Question 29

What is a placebo?

Answer 29

A substance which is used to mimic a drug in a trial but has no medicine in it- used as a control.

Question 30

describe the stages of a drugs trial

Answer 30

1. computer modelling
2. live cell test in a petri dish
3. Animal tests
4. stage 1 clinical trials on a small number of healthy volunteers
5. stage 2 clinical trials on a small number of patients with the disease
6. stage 3 clinical trials on a large number of patients

Question 31

What is an antitoxin?

Answer 31

A lymphocyte can produce a special sort of antibody which can bind with and neutralise toxins produced by a pathogen.

Question 32

What is meant by the term herd immunity

Answer 32

If the majority of people in a population have been vaccinated against a disease then it is unlikely to spread - herd immunity