Biology infection

What are communicable diseases?

Spread from person to person (e.g measles).

Spread by pathogens, such as bacteria or viruses.

What are non communicable diseases?

Cannot be assed from person to person (e.g coronary heart disease).

Define health:

The state of physical and mental well-being.

How can ill health be caused?

Poor diet containing too much fats (getting higher cholesterol)

High levels of stress

Other live situations (e.g working with harmful chemicals)

What is tuberculosis (TB)?

A communicable lung disease that is fatal.

For most people, the immune system can fight off TB.

However some have a defective immune system (e.g people with HIV)

Who might suffer from infectious diseases more often?

People with a defective immune system.

How can diseases sometimes be triggered by the immune system?

The body is infected with a pathogen which the immune system fights off but the person is then left with an allergy.

How might a physical illness trigger a mental illness?

A physical illness like arthritis (not being able to move properly) can cause them to feel more isolated and then depressed.

Define what a pathogen is:

Microorganisms that cause infections disease.

What are examples of pathogens?

Bacteria, viruses, fungi and protists.

How can bacteria make us ill?

Once inside the body, bacteria can reproduce very rapidly. They release harmful chemicals called toxins. Toxins damage tissues which make us feel ill.

Explain what viruses are:

Cannot reproduce by themselves. Only reproduce when inside a host cell.

How does a virus make us ill?

Virus invades the host cell.

The virus then reproduces inside the host cell.

This is very damaging to the cell. When the virus leaves the cells it can cause the cell to burst open and die.

How do pathogens spread?

• Some pathogens spread in the air (e.g in wager droplets (influenza))

• Spread directly in water (e.g cholera)

• Spread by direct contact between individuals (e.g HIV)

How can HIV spread?

Through shared needles (drug addicts may get HIV easily) and through sex.

How can we reduce the spread of pathogens?

• Washing your hands before eating.

• Providing people with clean drinking water (in UK, water contains chlorine which kills microbes).

• Using a condom during sexual intercourse to reduce the spread of HIV.

• Highly infectious diseases require isolation (e.g Ebola).

• Vaccination.

True or false: “viruses cannot be killed by antibiotics".

True.

What are the symptoms of measles?

• Fever

• Red skin rash

How is measles spread?

Infected person coughs or sneezes. The viruses then passes into a different person when droplets are inhaled.

Why is measles seen as a serious disease?

Can damage the breathing system and the brain. So most people are vaccinated.

What are the symptoms of HIV?

• Flu-like illness (disappears after 1-2 weeks).

What does HIV do?

Virus attacks the cells. Causing the immune system to become severely damaged. The patients immune system becomes so bad that they can't fight other infections that others find easy to deal with.

How can HIV be treated?

Taking antiretroviral drugs to stop the virus from multiplying inside the patient so the immune system doesn't become damaged.

How might patients not develop AIDS when they have HIV?

Taking antiretroviral drugs which lets them have a normal life expectancy.

What is a misconception about antiretroviral drugs?

People think they can cure HIV or AIDS. A patient has to take these drugs for the rest of their life.

Are salmonella food poisoning and gonorrhea communicable or non communicable?

Communicable.

True or false: “bacteria can't be killed using antibiotic”.

False.

How is salmonella caused?

The bacteria that causes salmonella food poisoning is spread by injesting infected food (unhygienic conditions).

The bacteria secrete harmful chemicals called toxins.

• What are the symptoms of salmonella?

• Fever

• Abdominal cramps

• Vomitting

• Diarrhoea

Why are all chicken in the UK vaccinated?

They are vaccinated against salmonella. This controls the spread of the disease.

How do people get gonorrhoea?

Through sexual intercourse.

What are the symptoms of gonorrhoea?

• Thick yellow/green discharge from penis of vagina.

• Pain when urinating.

How do you prevent the spread of gonorrhoea?

• Using a condom through sexual intercourse to prevent bacteria from passing person to person.

• Being tested for gonorrhoea to them be treated with antibiotics to kill the bacteria.

Is malaria a non communicable or communicable diseases?

Communicable.

What type of pathogen is malaria?

A protist.

What are symptoms of malaria?

• Repeated bouts of fever

• Fatigue

• Chills

• Seizures

How does malaria spread?

Infected person is bitten by a mosquito. The malaria pathogen passes into the mosquito, who bites a different person.

Why is a mosquito a vector?

It carries the pathogens from one person to another in malaria.

How can you prevent the spread of malaria?

• Stop the vector (mosquito) from breeding → they breed in still water so you must drain them.

• Use insecticide sprays (in still water)

• Sleeping with mosquito net.

What is the job of the non specific defence system?

Prevent patjogend from entering the human body.

How does your skin protect the body?

• Forms a protective layer over your body.

• The outer layer consists of dead cells which make it difficult for pathogens to penetrate.

• Skin produces oily substance called sebum which kills bacteria.

What do scabs on skin prevent?

Prevent pathogens from entering body.

How does the nose prevent pathogens from entering?

• Contains hair and mucus which trap pathogens.

• However some pathogens enter→ trachea and bronchi are covered in tiny hairs called cilia.

How does cilia stop pathogens from entering

Covered in mucus which can trap pathogens.

Cilia waft the mucus upwards towards the throat where it is swallowed into the stomach.

How does the stomach fight against pathogens?

• Stomach contains hydrochloric acid.

• This kills pathogens before they make their way further down the digestive system.

What does the immune system do to pathogens?

It destroys pathogens and any toxins they produce.

It then protects us incase the same pathogen invades again in the future.

Describe phagocytosis.

• The white blood cells detect chemicals released from the pathogen and moves towards it.

• The white blood cells then ingests the pathogens.

• Then use enzymes to destroy the pathogens .

What are antibodies?

Protein molecules produced by white blood cells.

How do antibodies kill pathogens?

Antibodies stick to pathogens which triggers them to be destroyed.

Why won't antibodies work with other pathogens?

Antibodies are extremely specific. They will not against any other pathogen.

How do antibodies protect us if we get infected by the same pathogen again?

They remain in blood for a long time.

How do antitoxins prevent cells from being damaged?

• White blood cells can produce antitoxins.

• They stick to toxin molecules and prevent them from damaging cells.

How does vaccination work?

• Involves introducing small quantities of dead/inactive forms of a pathogen into the body.

• White blood cells are now stimulated to produce antibodies against the dead/inactive pathogen.

• White blood cells divides by mitosis to produce lots of copies (stay for decades). Preventing infection.

What is herd immunity?

When an unvaccinated person doesn't get ill due to the large amount of vaccinated people.

They can't get the disease as no one around them can pass the pathogen on.

What do antibiotics do?

They kill infective bacteria inside the human body, without harming body cells.

Why are certain antibiotics no longer effective on certain bacteria? What is this term called?

Antibiotics can become overused. The bacteria evolved so it can't be killed by the antibiotic. This is known as antibiotic resistance.

Can antibiotics kill viruses?

No.

What do painkillers do?

They treat the symptoms of a disease by relieving pain. But they cannot kill pathogens.

Why is it difficult to develop drugs that kill viruses?

Viruses live and reproduce inside human cells. This means the body's tissues can be damaged with a drug that kills a virus.

What was the plant foxglove used for?

Foxglove used to extract the heart drug digitalis.

What was the painkiller aspirin extracted from?

Willow trees

What was penicillin found in?

In the mould penicillium.

Who discovered penicillin?

Alexander Fleming.

What do we check when testing new drugs? (TED)

• Toxicity: check if it's safe for humans.

• Effective: if it treats the disease.

• Dosage: check if the amount is safe.

1. (C) - cells/tissues used for preclinical testing.

2. (A) - animals used for testing.

3. (V) - volunteers given small amounts for Clinical testing to find optimal dose

4. (I) - Ill patients are given the drug.

5. (P) - peer review is done by other scientists to prevent bias and to ensure the drug is safe and correct.

What is a placebo?

A tablet or injection with no active drug in it.

Why do some patients get better when given the placebo?

They think they're treated so they believe they're going to get better.

Describe a double blind trial:

The test group receive the active drug.

The placebo (control group) receive a test drug without the active ingredient.

Neither the patient nor doctors know who has what → to stop bias.