Topic 3 - Infection and Response

What is a pathogen?

A pathogen is a microorganism that enters the body and causes a disease.

What are the 4 types of pathogens?

Viruses, Bacteria, Protists and Fungi.

What is bacteria?

Bacteria are very small cells which can reproduce rapidly in your body. They make you feel ill by producing toxins.

What are the two examples of bacteria you need to know?

Salmonella: This is a type of bacteria that causes food poisoning. They are found in contaminated foods like raw meat and eggs. They cause a fever, diarrhoea and vomiting. Fatal for elderly and young.

Gonorrhoea: This is a std. They have few symptoms but one is yellow discharge. It can be treated with antibiotics or barrier methods. Recently, the bacteria has grown antibiotic resistance.

What is a virus?

They are not cells. They reproduce rapidly in your body and replicate themselves in your cells, using the cells’ machinery to produce more until that cell bursts, releasing them. The cell damage make you feel ill.

What are the 3 examples of viruses?

Measles: A disease which spreads through droplets from an infected person’s sneeze or cough. Symptoms are red spots and rashes all over but it can cause pneumonia and a high fever which could be fatal. No treatment but vaccines.

HIV: An std from sharing bodily fluids like semen or blood from sharing needles. No symptoms for up to 8 years. It attacks white blood cells and the immune system. Ni cure as it mutates and can cause AIDS.

Tobacco Mosaic Virus: Plant pathogen that infects many plants like tomatoes. It causes a mosaic pattern on leaves and discolouration, stopping photosynthesis. No cure.

What is a protist?

A single celled eukaryotic often carried by a vector (Insect that carries the protist).

What is an example of a protist?

Malaria: It lives in mosquitoes cheeks and is spread when they bite humans and inject their spit. It targets red blood cells and the liver. It causes diarrhoea, liver damage and a fever. Its prevented with nets at night, chemicals and destroying their habitats.

What is a Fungi?

A pathogen which can grow on organisms and penetrate their skin.

What is an example of a fungi?

Rose black spot: A fungus that causes purple or black spots on rose plants. This leads to leas photosynthesis. It spreads through wind and water. It can be treated using fungicides.

How can your immune system attach pathogens?

With phagocytosis, antibodies or antitoxins.

What is phagocytosis?

Phagocytosis: The process in which white blood cells engulf and digests foreign cells.

What are antibodies?

On the outside of cells we have protein molecules that are unique to our body called antigens which inform the white blood cells its from our body. When a white blood cell finds a foreign antigen it produces a protein called an antibody. This antibody then finds the pathogen so white blood cells can destroy it. Then antibodies are produced rapidly round the body to find similar pathogens as they are made specifically for that antigen. This makes it so they are made much quicker next time they get that pathogen again.

What are antitoxins?

Antitoxins: An antibody that is released to neutralise toxins created by bacteria.

How do vaccines prevent future pathogens?

Pathogens are often a small amount of dead pathogens. They are injected so your white blood cells can produce antibodies to attack them. Now if that live pathogen appears later your white blood cell can rapidly produce antibodies kill it straight away.

What are antiseptics?

Something you put on your skin to kill pathogens.

What are analgesics?

Another name for painkillers.

What are antibiotics?

A medication used to kill bacteria.

What is antibiotic resistance?

When a bacteria that used to be killed by antibiotics is immune to them. This is done by when people stop taking antibiotics when they feel better even though there are still a few stronger bacteria in your body. They then reproduce and spread to others and this repeats until they are mostly immune.

What are drugs tested for?

They are tested for any extreme side effects, efficacy (if it works well), the dosage to five and if it can successfully enter and exit the body.

What are the stages of developing drugs?

Preclinical Testing: Testing on cells, tissue and animals to see if it’s safe on humans.

Stage 1: A small group of healthy people so it isn’t affected by other variables.

Stage 2: A small group of unhealthy people to see if it cures the disease.

Stage 3: A large group of people for rare side effects and the double blind test.

What is the double blind test?

This is when patients are either given a placebo (A substance like a drug that doesn’t do anything, sugar) or the new drug. Neither the patient nor the doctor knows this. This tests for the placebo effect, to see if the drug actually works or if it’s because the patient is told they will get better from it.

What are monoclonal antibodies?

These are identical antibodies which are made for a certain pathogen. This is done by injecting a mouse with a pathogen, and waiting for it to produce antibodies. The white blood cells of the mouse are then taken (mouse dies) and infused with cancer cells to make a hybridoma. This hybridoma then reproduces rapidly using mitosis and given to the patient suffering from the same disease injected onto the mouse. This is done so a pathogen can be treated immediately.

How do monoclonal antibodies treat diseases?

They are designed to attach to the pathogens antigens. An anti-cancer drug like chemotherapy is attached to the antibodies so it can kill the cell.

What two mineral ions do plants need?

Nitrate ions: These are needed to make proteins for growth and a lack of it can cause stunted growth.

Magnesium ions: These are needed to make chlorophyll for photosynthesis and a lack of it causes chlorosis and yellow leaves.

Plant physical defences?

Waxy cuticle: These prevent pathogens from entering the epidermis.

Dead cells: These prevent pests from entering the living cells.

Plant chemical defences?

Antibacterial chemicals: These kill bacteria

Poisons: These deter herbivores from eating it.

Plant mechanical defences?

Thorns and hairs: These stop animals from touching and eating them.

Drooping: Many plants droop or curl so insects fall when trying to eat them.