Lesson 3 : Infection and Response

Pathogen

Microorganisms that cause infectious disease

What are the 4 types of pathogens?

1. Bacteria

2. Fungi

3. Viruses

4. Protists

How does bacteria make you ill?

1. They reproduce rapidly inside body cells

2. They produce toxins that damage cells and tissues

How do viruses make you ill?

1. They live and replicate inside cells using the cells machinery, eventually causing the cell to burst open and die

What are the three ways pathogens spread?

1. Air

2. Water

3. Direct contact

How can the spread of disease be reduced or prevented?

1. Good Hygiene

2. Isolating infecting individuals

3. Destroying vectors (eg: using insecticides to kill mosquitoes)

4. Vaccination

What are 3 examples of viral diseases?

1. Measles

2. HIV

3. Tobacco Mosaic virus

What are the symptoms of measles?

Fever and a red skin rash

How is measles spread?

Inhalation of droplets from sneezes and coughs (Air)

How is measles prevented?

vaccination of young children

What the symptoms of HIV?

1. Causes an initial flu-like illness

2. Virus attacks the body's immune cells

3. Late stage HIV is known as AIDS, as the immune system is so badly damaged it can no longer deal with other infections

How is HIV spread?

Sexual contact or exchange of body fluids

How is HIV prevented/ treated?

1. Using contraception

2. Using antiretroviral drugs to control viral replication

What are the symptoms of Tobacco Mosaic virus?

1. Distinctive 'mosaic' pattern of discolouration in leaves

2. Affects growth of plant due to a lack of photosynthesis

What plants are primarily affected by TMV?

1. Tomato plants

2. Tobacco plants

What are 3 examples of bacterial diseases?

1. Salmonella

2. Gonorrhoea

What are the symptoms of salmonella?

1. Fever

2. Abdominal cramps

3. Vomiting

4. Diarrhoea

How is salmonella spread?

By eating contaminated food

How is salmonella prevented?

Vaccinating poultry

What are the symptoms of gonorrhoea?

1. Thick green/ yellow discharge from vagina or penis

2. Pain when urinating

How is gonorrhoea spread?

Sexual contact

How is Gonnorhea prevented/treated?

1. Using contraception

2. Treating with antibiotics

What is an example of a fungal disease?

1. Rose black spot

What are the symptoms of rose black spot?

1. Purple or black spots develop on leaves which turn yellow and drop early

2. Reduces plant growth due to less photosynthesis

How is rose black spot spread?

Through water and the wind

How is rose black spot prevented/ treated?

1. Using fungicides

2. Removing and destroying affected leaves

What is an example of a protist disease?

1. Malaria

What are symptoms of malaria?

1. Recurrent episodes of fever

2. Can be fatal

How is malaria spread?

By a vector (mosquitoes) that passes protist between hosts

How is malaria prevented?

1. Destroying vectors and stopping breeding

2. Using insecticides

3. Using mosquito nets

What are the 4 non specific defends systems of the human body against pathogens?

1. Skin

2. Nose

3. Trachea and bronchi

4. Stomach

How does the skin act as a non-specific defends system?

Provides a protective barrier that prevents pathogens entering the body

How does the nose act as a non-specific defends system?

Contains tiny hairs that trap pathogens which you can then remove through sneezing/ blowing nose

How do the trachea and bronchi act as a non-specific defends system?

Contain ciliated epithelial cells which contain mucus that trap bacteria. The mucus is wafted up to the nose where it can then be sneezed out or swallowed

How does the stomach act as a non-specific defends system?

Contains hydrochloric acid that destroys pathogens

What are the two types of white blood cells?

1. Phagocytes - engulf and destroy pathogens

2. Lymphocytes - produce antibodies that bind to foreign antigens

What are three ways white blood cells defend the body against pathogens?

1. Phagocytosis

2. Antibody production

3. Antitoxin production

Explain how a vaccine prevent the illness of an individual?

A dead or inactive forms of a pathogen are introduced in small quantities into the body to stimulate the production of antibodies by lymphocytes. If the same pathogen then re-enters the body the white blood cells respond quickly to produce the correct antibodies, preventing infection.

What is herd immunity?

When the majority of the population is vaccinated against a disease

Explain how the spread of pathogens can be reduced by immunising a large proportion of the population

When a higher percentage of the population is immune, there is less chance of an unvaccinated individual coming into contact with an individual who is infected. This leads to transmission slowing down or stopping entirely, meaning the disease cannot spread throughout the community

What is an antibiotic?

A drug that kills bacteria without harming body cells

What is antibiotic resistance?

The ability of bacteria to survive exposure to antibiotics, caused by mutations in their genes

Why can antibiotics not kill viruses?

They cannot kill viruses because they live and reproduce inside body cells

What are painkillers?

Drugs that relieve pain (they do not kill the pathogen)

What is the source of the heart drug digitalis?

Foxgloves

What is the source of the painkiller aspirin?

Willow tree bark

What is the source of the antibiotic penicillin?

Mould

Who discovered penicillin?

Alexander Fleming

What are the 3 criteria new drugs are tested for?

1. Efficacy (effectiveness)

2. Toxicity (any potential side effects)

3. Dosage (safest and most effective concentration)

What are the two stages of preclinical testing?

1. Drug is tested on human cells and tissues

2. Drug is tested in live animals

What are the two stages of clinical trials?

1. Drug is tested on healthy volunteers

2. Drug is tested on individuals suffering from the illness

Why is the drug tested on healthy volunteers?

To make sure that it doesn't have any harmful side effects when the body is functioning normally and to identify the max dosage without side effects

What is searched for when testing on individuals with the illness?

To identify optimum dosage (max efficacy min toxicity)

How is the process ensured to be fair and avoid bias?

1. Clinical trials are double blinded (with placebo)

2. Results undergo peer reviewing

What is the process of producing monoclonal antibodies?

1. Antigen is injected into a mouse

2. Mouse naturally produces B-lymphocytes, which produce antibodies specific to the antigen

3. B-lymphocytes that produce the antibody are extracted

4. B-lymphocytes are fused/ combined with a fast dividing tumour cell to form a hybridoma

5. Antibodies are produced in large quantities, and are then collected and sterilised

What are 3 uses of monoclonal antibodies?

1. For diagnosis in pregnancy tests

2. In labs to measure hormone levels or other chemicals in blood

3. To treat some diseases (eg: cancer)