Disease, Defence & Treatment (WJEC GCSE Science (Double Award): Biology): Flashcards

True.

Antibiotic production is one of several industrial and medical uses of beneficial micro-organisms.

Hygiene, sanitation and disease control must remove pathogens without destroying the beneficial micro-organisms that maintain public health and environmental stability.

• Bacteria

• Viruses

• Protists

• Fungi

• A cell wall

• A cell membrane

• Cytoplasm

• No distinct nucleus

Genetic material, either DNA or RNA, surrounded by a protein coat.

Some viruses also have an outer envelope.

They can only exist inside the living cells of other organisms, which they take over in order to make copies of themselves.

They reproduce very quickly and produce toxins that damage cells.

A disease that can transfer from a diseased host to a healthy organism, i.e. an infectious disease.

• By contact

• By aerosol, droplets in the air

• By body fluids

• By water

• By insects

• By contaminated food

• Aerosol: the common cold or influenza

• Insects: malaria or dengue fever

Any two of:

• Cholera

• Typhoid

• Dysentery

• Salmonella

• HIV

• Hepatitis

A bacterial cell has a cell wall, cell membrane and cytoplasm but no distinct nucleus.

A virus consists of genetic material surrounded by a protein coat.

False.

Many bacteria, fungi and protists are harmless and do not cause disease. Only some species are pathogenic.

False.

Viruses do not carry out the life processes themselves. They take over a host cell's machinery to replicate.

• Bacterial: tuberculosis or cholera

• Viral: measles or HIV

• Protist: malaria

• Intact skin forming a barrier against micro-organisms

• Blood clots to seal wounds

• Phagocytes ingesting micro-organisms

• Lymphocytes producing antibodies and antitoxins

It forms a physical barrier covering almost the whole body, making it difficult for pathogens to get in.

They seal wounds by forming a scab, which prevents pathogens from entering through the break in the skin.

A type of white blood cell that engulfs and digests pathogenic cells.

A type of white blood cell that produces antibodies and antitoxins.

A protein produced by lymphocytes that neutralises the toxins produced by bacteria.

They clump the pathogens together so they cannot move easily.

They also release chemicals that signal to phagocytes that those cells must be destroyed.

The community of micro-organisms living on the skin surface.

They compete with invading pathogenic bacteria, preventing them from becoming established.

Phagocytes are white blood cells that engulf and digest pathogens.

Lymphocytes produce antibodies and antitoxins, which neutralise bacterial toxins.

True.

Both are white blood cells, but they defend the body in different ways.

False.

Clotting also prevents pathogens entering the body through the wound.

The intact skin barrier is broken, so pathogens can enter the body directly until a blood clot seals the wound.

• Phagocytes physically engulf and digest the pathogen

• Lymphocytes produce antibodies that clump pathogens together and mark them for destruction

A molecule that is recognised by the immune system, found projecting from the surface of a cell membrane and specific to that type of cell.

A protein made by lymphocytes that is complementary in shape to a specific antigen.

They are triggered to secrete antibodies that are specific to that antigen.

• They attach to antigens and clump the pathogens together so they cannot move easily

• They release chemicals that signal to phagocytes that those cells must be destroyed

Its shape is complementary to the shape of that particular antigen, so it will not fit any other.

It takes a few days for a lymphocyte to identify the specific antibody needed and then clone itself to produce antibodies in large quantities.

• Antigen: a molecule on the surface of a cell

• Antibody: a protein made by lymphocytes, complementary to an antigen

• Antitoxin: a protein that neutralises bacterial toxins

The clumped pathogens cannot move easily, so they are more easily destroyed by phagocytes.

An antibody has a shape that is complementary to the antigen it acts against.

Antibodies are produced by white blood cells called lymphocytes.

False.

Each antibody is specific to one antigen, because its shape is complementary to that antigen alone.

True.

They 'read' the antigens on cell surfaces and identify any that do not belong to the body.

Cold viruses mutate, so their antigens change.

The existing antibodies no longer fit, so a new immune response is required each time.

It clones itself many times, so antibodies can be produced in large quantities.

In childhood, with parents deciding whether their child is vaccinated.

• The science behind the vaccine

• Media representation

• The perceived risks and benefits

The protection that arises when a large proportion of a population is vaccinated, making it unlikely that an unvaccinated individual will become infected.

It reduces the chance that an infected person spreads the pathogen to others, helping to prevent the disease spreading through the population.

Any three of:

• Smallpox

• Measles

• Mumps

• Tetanus

Any three of:

• Vaccines may only be effective for a limited time

• Vaccination does not always give immunity

• Vaccines may be difficult to access or must be paid for

• Concerns about side effects or other conditions

A 1998 study of 12 children concluded the MMR vaccine might cause autism.

One of the doctors was later found to be advising parents suing the vaccine manufacturers, and extensive later research has found no such link.

A wave of parents refused the MMR vaccine, lowering uptake and reducing the chance of achieving herd immunity.

• Measles

• Mumps

• Rubella

When a large proportion of a population is vaccinated, the resulting protection is called herd immunity.

Smallpox is a disease that has been eradicated worldwide by vaccination.

False.

Despite extensive research since 1998, no link has been found. The original study has been thoroughly discredited.

True.

Herd immunity requires a large proportion of the population to be vaccinated.

If most people around them are immune, the pathogen has few hosts to spread through.

The unvaccinated person is therefore unlikely to ever come into contact with it.

Antigens derived from a disease-causing organism.

This may be specific antigens, parts of antigens, or non-active micro-organisms such as dead or weakened virus particles.

The antigens are introduced into the body, usually by injection.

Lymphocytes produce complementary antibodies against those antigens.

Memory cells are created and remain in the blood.

If the live pathogen is later encountered, the memory cells respond quickly, destroying it before illness develops.

The antigens or micro-organisms are rendered harmless, so they cannot cause illness but can still provoke an immune response.

Bacterial or viral particles are grown in a laboratory and then rendered harmless.

Lymphocytes, a type of white blood cell.

Memory cells are produced and remain in the blood for a long time, ready to respond if the antigen is met again.

Both types of pathogen carry antigens on their surface.

A vaccine containing those antigens triggers the same lymphocyte and memory cell response, whichever pathogen they came from.

A vaccine contains antigens derived from a disease-causing organism.

After vaccination, memory cells remain in the blood ready to respond to a future infection.

False.

Vaccines contain antigens, parts of antigens, or dead or weakened micro-organisms, which cannot cause illness.

False.

The vaccine provokes the body's own lymphocytes to make antibodies and memory cells.

The memory cells recognise the antigen immediately and produce antibodies quickly and in large quantities, destroying the pathogen before symptoms develop.

A cell that remains in the body after an antigen has been encountered, allowing antibodies to be produced very quickly if the same antigen is met again.

It takes several days to find the specific lymphocyte, which must then clone itself before producing antibodies.

The pathogen multiplies during this delay, causing symptoms.

Antibodies are produced:

• More quickly

• In larger concentrations

Memory cells are already present.

They detect the antigen, clone themselves and produce the specific antibody without the delay of finding the right lymphocyte.

The pathogen is eliminated before it can multiply enough to cause illness.

• Following a natural infection

• Following vaccination

Memory cells only recognise the one antigen they were formed against.

They give no protection against a different pathogen.

Many years, which is why the immunity gained from an initial immune response can be long-term.

The primary response is slow and low, with a delay before antibodies appear.

The secondary response is much faster and much higher, because memory cells are already present.

Memory cells remain in the blood after an infection has gone.

The presence of memory cells means a person is said to be immune to that pathogen.

False.

The memory cell response is highly specific to the antigen that produced it.

Flu viruses mutate, changing their antigens.

Existing memory cells no longer recognise them, so a completely new immune response is needed.

A chemical drug that kills bacteria or prevents their growth, originally produced by living organisms such as fungi.

They kill the infecting bacteria or prevent them from growing and reproducing, by disrupting structures and processes specific to bacterial cells.

Antibiotics target processes and structures that are specific to bacterial cells. Viruses do not have them.

They target features that are specific to bacterial cells, which animal cells do not share.

Penicillin, discovered in 1928 by Alexander Fleming.

Fleming noticed that bacteria left in a Petri dish had been killed by a naturally occurring Penicillium mould, which produces a chemical that prevents bacterial infection.

Antibiotics were originally medicines produced by living organisms such as fungi.

False.

A cold is caused by a virus, and antibiotics have no effect on viruses.

Methicillin-resistant *Staphylococcus aureus, a dangerous bacterial strain resistant to most antibiotics*, which makes it very difficult to treat.

Random mutation makes a few bacteria resistant.

When antibiotics are used, the resistant bacteria survive while the rest die.

They then reproduce with less competition, so the resistance genes spread until the whole population is resistant.

• Treating non-serious infections

• Routine treatment of animals in agriculture

• Patients failing to finish a prescribed course

Patients there are already in poor health, so the risk of serious infection is much higher, and antibiotics are used heavily.

• Thorough hand washing, especially between patients

• Thorough cleaning of wards

• Frequent use of alcohol gels

• Screening of patients and staff for MRSA

Resistant strains such as MRSA arise as a result of the overuse of antibiotics.

True.

A very short generation time means natural selection acts over a much shorter period than in most organisms.

As more strains become resistant, there are fewer new antibiotics available to treat infections that existing drugs can no longer control.

• Good hygiene

• Access to clean water

• An improved diet

• Vaccination

• Drugs, such as anti-malarials

Hand washing before eating and after using the toilet.

Many diseases, such as cholera, are carried in unsanitary water.

Plenty of fresh fruit, vegetables and whole foods supports the immune system.

A poor diet is linked to cardiovascular disease and some cancers.

• Measles

• Whooping cough

Anti-malarial drugs, taken before and during travel to areas where malaria is present.

It must be treated, often with medicinal drugs such as antibiotics.

Access to clean water is vital for preventing diseases such as cholera.

Anti-malarial drugs can be taken to prevent malaria rather than to treat it.

True.

Prevention avoids the illness entirely, whereas treatment only deals with a disease once someone is already unwell.

False.

Some diseases cannot be prevented, and in other cases the necessary steps are not taken. Those must then be treated.

It removes pathogens from the hands before they can be transferred to the mouth, to food, or to another person.

• Toxicity: does it have harmful side effects?

• Efficacy: does the drug work?

• Dose: what is the lowest dose that still has an effect?

Some side effects only appear once large numbers of people are taking the drug, so smaller trials may miss them.

It can be considered cruel, causing pain and distress. Animals are kept in small, unnatural cages and may be harmed by the drug.

Some people consider it necessary to ensure the safety of humans, and laboratories follow strict protocols to meet the animals' basic needs.

Animal testing is not foolproof, because animals metabolise medicines differently from humans.

Alternatives such as computer models could give more relevant results without using animals.

True.

Many early medicines, including penicillin, came from living organisms before drugs were designed in laboratories.

True.

Extensive testing allows large-scale data collection that minimises the risks, while the new treatments save and improve many lives.