Infection And Response

What are pathogens?

· Microorganisms that cause infectious diseases.

· 4 types - bacteria, viruses, protists and fungi.

What are communicable (infectious) diseases?

· Caused by pathogens.

· Passed / spread from person to person.

How do bacteria make you feel ill?

Produce toxins (poisons) that damage cells.

How do viruses make you feel ill?

Reproduce inside the cells, damaging them.

What type of of pathogen causes measles?

Virus

How is measles spread from one person to another person?

Breathing in droplets that contain the virus from the sneezes / coughs of an infected person.

How can the spread of measles be reduced?

Vaccinate young children

What type of of pathogen causes HIV?

Virus

How is HIV spread from one person to another person?

· Sexual contact

· Exchange of blood when drugs users share needles.

How can the spread of HIV be reduced?

· Do not share needles.

· Use a condom or don't have sex.

What are the symptoms of measles?

· Red skin rash

• fever

What are the symptoms of tobacco mosaic virus?

· Mosaic pattern of discolouration on leaves.

• reduced growth due to lack of photosynthesis

How is tobacco mosaic virus spread from one plant to another plant?

Direct contact between diseased and healthy plants.

How can the spread of tobacco mosaic virus be reduced?

· Remove and destroy infected leaves / plants.

· Wash tools in disinfectant after using on an infected plant.

What type of pathogen causes salmonella food poisoning?

Bacteria

How is salmonella spread from one person to another person?

Eating the bacteria in or on food e.g. chicken or eggs.

How can the spread of salmonella be reduced?

· Vaccinate chickens.

• Cook food thoroughly

What are the symptoms of gonorrhoea?

· Thick yellow or green discharge from penis or vagina.

• Pain when urinating

How is gonorrhoea spread from one person to another person?

Sexual contact

How can the spread of gonorrhoea be reduced?

· Use a condom or don't have sex.

• Treatment with antibiotics

What type of pathogen causes rose black spot?

Fungi

What are the symptoms of rose black spot?

· Purple / black spots on leaves.

· Leaves often turn yellow and drop of the plant.

· Reduced growth due to lack of photosynthesis

How is rose black spot spread from one plant to another plant?

By water or wind.

How can the spread of rose black spot be reduced?

· Remove and destroy affected leaves.

• Treatment with fungicides

What type of pathogen causes malaria?

Protist

How is malaria spread from one person to another person?

Mosquito bites

How can the spread of malaria be reduced?

· Use mosquito nets or insect repellent to avoid being bitten.

•· Prevent mosquitos from breeding e.g. by draining swamps where they lay their eggs or kill the mosquitoes e.g. use insecticides. Because there are less mosquitos you are less likely to be bitten.

How does the body try and stop pathogens from getting in?

skin

•acts as a barrier

• scabs over cuts

nose

•hair and mucus trap pathogens that enter

airway (trachea and bronchi)

• produce mucus which traps pathogens

• cilia (not hairs!) waft the mucus and trapped pathogens up to the throat to be swallowed

Stomach

· Contains hydrochloric acid which kills pathogens in food and swallowed mucus.

How do the white blood cells try and destroy any pathogens that enter the body?

1. Engulf (take up) and digest (break down) the pathogen.

2. Produce antibodies which bind to antigens on the pathogen and destroy the pathogen.

3. Produce antitoxins which bind to and neutralize the toxins released by the pathogen.

How does vaccination make a person immune to a disease?

1. An inactive form of the pathogen is injected into body.

   2. Antigens (on its surface) stimulate white blood cells to produce specific antibodies.

   3. Memory cells, which are type of white blood cells, are produced and remain in the body.

   4. If the real pathogen gets into the body, the white blood cells produce large amounts of specific antibodies quickly.

   5. This means the pathogen is killed before the pathogens numbers are high enough to cause any damage to the body. Therefore, the person has no symptoms.

How does vaccination reduce spread of a pathogen?

If we vaccinate a large proportion of the population it stops the disease from spreading.

If a person has not had the vaccine then it is very unlikely that they meet somebody with the disease.

Why are bacteria classed as prokaryotic cells?

Don't have a nucleus

Why aren't viruses classed as cells?

Don't have a cell membrane or cytoplasm.

All cells have a cell membrane and cytoplasm.