Infection and Response

Flashcards made from section 4.3 (‘Infection and response’) from the AQA GCSE Biology (8461) specification.

What are communicable diseases?

Communicable diseases are diseases that can be spread from person to person (infectious/contagious)

What are pathogens?

Pathogens are micro-organisms that cause infectious disease

What are the 4 types of pathogen (for GCSE?)

The four GCSE pathogens are: ★ Bacteria ★ Viruses ★ Fungi ★ Protists

How does bacteria make us ill?

How bacteria makes us ill?

1. They multiply very rapidly inside cells (as much as doubling every twenty minutes)

2. They then release harmful chemicals (toxins) ➜ Toxins damage tissues and make us feel ill

True or False: viruses can only replicate inside a host cell

True, viruses need a host cell to replicate

How do viruses cause damage and makes us feel ill?

★ Viruses multiply rapidly inside the cell ➜ This causes to burst open and die ✔︎ The cell damage is what makes us feel ill

How are pathogens spread?

Pathogens can be spread: ★ Through the air (e.g. influenza virus) ★ Through water (e.g. cholera) ★ Direct contact (e.g. HIV)

How can we reduce the spread of pathogens?

We can reduce the spread of pathogens by: ★ Basic hygiene (e.g. washing hands) ★ Access to clean drinking water ★ Reduce direct contact (e.g. using a condom) ★ Isolated infected people (for highly infectious diseases) ★ Vaccination

What 3 GCSE diseases are viral diseases?

The 3 GCSE viral diseases are: ★ Measles ★ HIV ★ Tobacco mosaic virus (TMV)

Are viruses curable via antibiotics?

No, viruses cannot be treated via antibiotics

What is measles?

Measles is a viral disease showing symptoms of fever and a red skin rash.

Is measles life-threatening?

Yes, measles is life-threatening

How do we prevent people from getting measles?

To stop people getting measles, we vaccinate young children

How is measles spread?

The measles virus is spread by inhalation of droplets from sneezes and coughs.

What organs are affected by measles?

The brain and the heart are affected by measles

What does HIV initially cause?

HIV initially causes a flu-like illness

What will HIV do?

HIV attacks the body's immune cells

How do we stop HIV from attacking immune cells?

People with HIV have to take antiretroviral drugs for life to prevent HIV from attacking their immune cells

What is AIDS also called?

AIDS is also called late stage HIV infection

What does AIDS occur?

AIDS occurs when the body's immune system becomes so badly damaged it can no longer deal with other infections or cancers.

How is HIV spread?

HIV is spread by sexual contact or exchange of body fluids such as blood which occurs when drug users share needles.

What is TMV (Tobacco Mosaic Virus)?

Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes.

What does TMV do and what does it result in?

It gives a distinctive 'mosaic' pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis.

What two GCSE communicable diseases are caused by bacteria?

Bacterial diseases include: ★ Salmonella ★ Gonorrhoea

How do we kill bacteria?

To kill bacteria, we use antibiotics

How is salmonella spread?

Salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions.

What does salmonella produce that causes the symptoms of salmonella?

Salmonella secrete (produce) harmful chemicals called toxins which cause the symptoms of salmonella

What are the symptoms of salmonella?

The symptoms have salmonella include: ★ Fever ★ Abdominal cramps ★ Vomiting ★ Diarrhoea

What animals are salmonella found in?

Measles can be found in poultry such as chicken

How is the spread of Salmonella controlled in the UK?

In the UK, poultry are vaccinated against Salmonella to stop the spread of salmonella

How is gonorrhoea spread?

Gonorrhoea is a sexually transmitted disease (STD)

What are the symptoms of gonorrhoea?

Symptoms of gonorrhoea are: ★ Having a yellow/green discharge from the penis or vagina ★ Pain while urinating

Why have some antibiotics e.g. penicillin becoming ineffective when treating gonorrhoea? What is the solution?

★ The salmonella bacteria has become anti-biotic resistant ➜ Different antibiotics are now used

How can we stop the spread of gonorrhoea?

You can stop the spread of gonorrhoea by: ★ Using a condom during sexual intercourse ➜ This prevents the spread of bacteria from person to person ★ People who have unprotected sex should be tested for gonorrhoea ➜ If they have gonorrhoea, they can be treated with antibiotics to kill the bacteria before they spread it.

What GCSE communicable disease is caused by a fungus?

Rose black spot is cause by a fungus

What are the symptoms of rose black spot?

The symptoms of rose black spot include: ★ Leaves to develop purple/black spots ➜ These leaves often turn yellow and fall off

How is rose black spot spread?

Rose black spot is spread as the fungus can be spread by water or by wind

How can we treat rose black spot?

We can treat rose black spot by: ★ Spraying the plants with chemicals which kill fungi (fungicides) ★ Remove affected leaves and destroy them

What GCSE communicable disease is caused by a protist?

Malaria is caused by a protist

What are the symptoms of malaria?

The symptoms of malaria include: ★ Repeated bouts of extreme fever ★ Shaking

is malaria a life-threatening disease?

Malaria can be fatal (it can kill you)

How is malaria spread from person to person?

Malaria is spread by:

1. The infected person is bitten by a mosquito. The malaria pathogen passes into the mosquito

2. The mosquito bites a different person and passes the malaria pathogen to them

What is a vector in biology?

A vector is any organism that can spread a disease.

How can we prevent the spread of malaria? [simple answers]

The spread of malaria can be prevented by: ★ Preventing the vector (the mosquito) from breeding ★ Prevent mosquitoes from biting humans

How can we stop mosquitoes from breeding?

We can stop mosquitoes from breeding by: ★ Mosquitos breed in still water 𐬽 ★ We can find areas of still water and drain them 𐬽 ★ Spray areas of still water with insecticides ⚠︎︎ However, it is virtually impossible to kill all mosquitoes

How can we prevent mosquitoes from biting humans?

★ One of the best ways of preventing mosquitoes from biting humans is sleeping under a mosquito net ✔︎ This is because the mosquito can't go through the mosquito net ✔︎ It can also be sprayed with insecticide so the mosquito dies on landing

What is the job of the non-specific defence system?

The non-specific defence system prevents pathogens from entering the human body

How is the skin adapted to defend against the entry of pathogens?

The skin is adapted to defend against the entry of pathogens as it: ★ Forms a protective layer covering the human body ★ The outer layer of the skin consists of dead cells ➜ This is difficult for pathogens to penetrate ★ The skin produces an oily substance called sebum which kills bacteria

How does the skin resolve skin damage? Why is this a problem?

⚠︎︎ If the skin is damaged, pathogens could enter ✔︎ To stop this, the skin scabs over

How is the nose adapted to prevent pathogens from entering the body?

The nose is adapted to prevent pathogens from entering the body as it: ★ The nose contains hairs and mucus ➜ This traps pathogens before they enter the breathing system

How are the lungs adapted to prevent pathogens from entering the body?

The lungs are adapted to prevent pathogens entering the body as: ★ The trachea and bronchi are covered with tiny hairs called cilia ★ Cilia are covered in mucus which can trap pathogens ➜ The cilia now waft (gently move through the air) the mucus upwards towards the throat where it is swallowed into the stomach

How is the stomach adapted to prevent pathogens from entering the body?

The stomach is adapted to prevent pathogens from entering the body as: ★ The stomach contains hydrochloric acid (HCl) ➜ This kills pathogens before they can make their way further down into the digestive system

What are the two functions of the immune system?

The immune system's functions are: ★ Destroys pathogens and any toxins they produce ★ Protects us in case the same type of pathogen invades us again in the future

What 3 GCSE methods does the immune system use to combat disease?

The immune system use the following to combat disease: ★ Phagocytosis ★ Antibodies ★ Antitoxins

What is phagocytosis?

Phagocytosis is:

1. The white blood cells detects chemical released from the pathogen and moves towards it

2. The white blood cell then ingests the pathogens ⚠︎︎ Make sure you use 'ingest' instead of 'eat' [or else you will lose marks] The white blood cell uses enzymes to destroy the pathogens

What is the structure of antibodies?

Antibodies are protein molecules

What do antibodies do?

Antibodies bind to antigens on pathogens to disable and clump them together ready for phagocytosis

How do antibodies from white blood cells combat pathogens?

Antibodies combat pathogens by:

1. The white blood cell releases antibodies (protein molecules)

2. The antibodies stick to the pathogens ➜ This triggers the pathogens to be destroyed (via phagocytosis)

Do antibodies work for all pathogens?

No, antibodies do not work for all pathogens ★ Antibodies are extremely specific: they only work for one type of pathogens ✔︎ For example, someone who catches measles will produce measles antibodies which will only work against measles

How long do antibodies last in the blood? How is this useful? [Vague answer is acceptable]

Antibodies stay in the blood for a long time ★ This means they can protect us in case we ever get infected again with the same pathogen.

How do antitoxins combat toxins released by bacteria?

★ Antitoxins produced by white blood cells stick to toxin molecules and neutralise them ➜ This prevents them from damaging cells

When are almost all people vaccinated?

Most people are vaccinated when they are very young

How does vaccination work?

1. Small quantities of dead or inactive forms of a pathogen enter the body ➜ Since the pathogen is dead or inactive, it cannot lead to the disease in the patient

2. White blood cells are now stimulated to produce antibodies against the dead or inactive pathogen

3. While 2) is happening, the white blood cells divide by mitosis to produce lots of copies by itself

What happens if a vaccinated person receives a pathogen?

★ When someone is vaccinated, the white blood cells stay in a person's blood for decades ➜ This means, when the same pathogen enters years later, the white blood cells can produce the antibodies quickly and more antibodies are produced ➜ This prevents infection

True or False: the amount of antibodies produced when the real pathogen comes is less than when the person was vaccinated

False, the amount of antibodies produced is more when a person gets vaccinated

What is herd immunity?

★ Some people in the population aren't vaccinated (e.g. they're from a foreign country, missed vaccination appointment) ★ However, if the majority of the population is vaccinated, it also prevents the unvaccinated person from receiving the disease ✔︎ This is called herd immunity

What is an example of an antibiotic?

An example of an antibody is penicillin

What are antibiotics?

Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body.

Are antibiotics specific?

Antibiotics are specific to the bacteria

Do antibiotics work against viruses?

No, antibiotics don't work against viruses, because antibiotics target bacteria.

Why is it difficult to develop drugs that kill viruses?

It is difficult to develop drugs that kill viruses without also damaging the body's tissues (remember, viruses are inside a host cell)

What is antibiotic resistance?

★ Antibiotics are no longer effective as the bacteria has randomly mutated ➜ This means the antibiotic is no longer effective against the bacteria since it's a different bacteria

What increases antibiotic resistance?

Antibiotic misuse and overuse leads to antibiotic resistance

How do painkillers do?

★ Painkillers work by relieving/killing the pain ⚠︎︎ They do not kill pathogens

What can the plant foxglove be used for?

The plant foxglove was used to extract the heart drug digitalis

What can willow trees be used for?

The painkiller aspirin was extracted from willow trees

Who discovered penicillin?

Alexander Fleming discovered penicillin.

What does penicillin come from?

Penicillin comes from penicillin mould

How are new drugs made now?

★ Most new drugs are synthesised by chemists in the pharmaceutical industry. ✔︎ However, the starting point may still be a chemical extracted from a plant.

What three things are drugs tested for?

Drugs are tested for: ★ Efficacy ★ Toxicity ★ Dosage

What is the efficacy of a drug?

Efficacy is the maximum response achievable from a drug. (Is it effective?)

What is toxicity of the drug?

The toxicity of the drug is whether or not it is safe for humans

What is the dosage of a drug?

The dosage (of a drug) is the amount (of a drug)

What are the stages of preclinical testing?

1. Preclinical testing is done in a laboratory using cells, tissues

2. Using live animals

Who do clinical trials use?

Clinical trials use healthy volunteers and patients

What are the stages of clinical trials?

Clinical trials involve humans (after pre-clinical trials trials.) The stages are:

1. Very low doses of the drug are given at the start of the clinical trial.

2. If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug.

3. In double blind trials, some patients are given a placebo.

What is a placebo?

A placebo is a "fake" drug, often a sugar pill to see if improvements are psychological.

What is a double blind trial?

A double blind trial is where the patients AND researchers don't know if patients have the drug or placebo

What are side effects?

Side effects are reactions to medicines other than intended (usually bad)

What is antibody?

Antibodies are produced by white blood cells called lymphocytes

When do lymphocytes produce antibodies?

Lymphocytes produce antibodies when they come across a foreign antigen

What is an antigen?

An antigen is a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

How do we get lymphocytes from mice?

1. Inject a mouse with an antigen ★ Lymphocytes will form

2. Collect the lymphocytes

How do you produce a hybridoma cell? [Explain also the 'hybrid' part]

To produce a hybridoma cell, you: ★ Get a lymphocyte from a mouse ✔︎ Lymphocytes can produce antibodies ⚠︎︎ But they can't easily divide ★ Get a tumour cell ✔︎ Tumour cells can easily uncontrollably divide ⚠︎︎ They cannot produce antibodies 𐬽 We join (fuse) them together to produce the hybrid of the two, a hybridoma cell which can do both

How are monoclonal antibodies produced? [just last stages]

To get monoclonal antibodies, you: ★ Let hybridoma cells to divide by mitosis to form clone, identical hybridoma cells ✔︎ The antibodies produced by the hybridoma cells are called monoclonal antibodies

Why are monoclonal antibodies called monoclonal antibodies?

★ Mono - one ★ Clonal - to clone ★ Antibodies - antibodies ★ Monoclonal antibodies get formed by one hybridoma cell dividing to form clones which then produce antibodies, hence their name

[Briefly], how are monoclonal antibodies produced?

To get monoclonal antibodies, you: ★ Get lymphocytes from a mouse by injecting a foreign antigen ★ Fuse it with a tumour cell to obtain a hybridoma cell ➜ This hybridoma cell will divide by mitosis and from monoclonal antibodies

What is the benefit of monoclonal antibodies?

A benefit of monoclonal antibodies: ★ Can target a specific chemical or specific cells ➜ Have a large number of uses ★ We can produce monoclonal antibodies, antibodies against any antigen that we want

What are disadvantages of monoclonal antibodies?

Disadvantages to monoclonal antibodies include: ★ Unexpected side-effects ★ Not as useful as once expected

What is an example of monoclonal antibodies being used for diagnosis?

Pregnancy tests are an example of monoclonal antibodies being used for diagnosis