Preventing, Treating & Curing Diseases (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Flashcards

In the UK, Salmonella is controlled by:

1. Vaccinating poultry against the bacteria

2. Cooking and pasteurisation, which kill the bacteria

3. Maintaining hygienic food preparation conditions

False.

Gonorrhoea is caused by a bacterium, not a virus, and is spread through sexual contact rather than airborne droplets.

Gonorrhoea can be treated with the antibiotic penicillin, but many resistant strains have appeared. It can also be prevented by using a condom as a barrier method of contraception.

Measles causes fever and a red skin rash. It spreads by inhalation of droplets from the sneezes and coughs of infected individuals.

True.

Without treatment, HIV attacks the body's immune cells. Late-stage HIV — known as AIDS — occurs when the immune system can no longer fight other infections or cancers.

Complete the table comparing two communicable diseases.

HIV initially causes a flu-like illness. Without treatment, it attacks the body's immune cells, eventually leading to AIDS, where the immune system can no longer fight infections or cancers.

True.

Cooking and pasteurisation kill Salmonella bacteria, which is why properly cooking food is a key method of preventing food poisoning.

Non-specific defences are the body's first-line barriers against pathogens that act regardless of the type of pathogen — including the skin, nose, trachea and bronchi, and stomach.

The stomach produces acid which kills the majority of pathogens that enter the body through the mouth.

True.

The skin provides a physical barrier against pathogens and also produces antimicrobial secretions that help destroy pathogens that reach its surface.

The trachea and bronchi secrete mucus to trap pathogens. This is then moved by tiny hair-like structures called cilia towards the throat.

The four non-specific defences are:

1. The skin — a physical barrier with antimicrobial secretions

2. The nose — traps particles

3. The trachea and bronchi — secrete mucus moved by cilia

4. The stomach — produces acid to kill pathogens

True.

The nose catches airborne particles (including pathogens) in nasal hairs and mucus, preventing them from travelling deeper into the respiratory system.

Complete the table of non-specific defences.

They are called non-specific because they act as general barriers against all pathogens, regardless of the type — they do not target a particular pathogen.

An antigen is a molecule found on the surface of a pathogen (or cell) that triggers an immune response, leading to the production of specific antibodies.

White blood cells defend against pathogens by:

1. Phagocytosis — engulfing and digesting pathogens

2. Producing antibodies specific to the pathogen's antigens

3. Producing antitoxins to neutralise bacterial toxins

True.

Lymphocytes produce antibodies with a shape complementary to a specific antigen, meaning each antibody targets one type of pathogen.

Phagocytes engulf and digest pathogens in a process called phagocytosis.

An antitoxin is a protein produced by lymphocytes that neutralises the toxins released by bacteria, reducing the damage they cause to the body.

False.

Memory cells allow the immune system to respond more quickly to a second infection, producing the specific antibodies faster before the pathogen can cause harm.

It takes a few days for lymphocytes to produce sufficient antibodies specific to the pathogen's antigens. During this time, pathogens reproduce rapidly and produce toxins that damage cells and tissues.

Complete the table comparing immune response components.

A vaccine introduces weakened or inactive antigens into the body. The immune system responds by producing antibodies and memory cells specific to those antigens. If the same pathogen is encountered again, the memory cells allow a rapid antibody response before the pathogen can cause harm.

Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate white blood cells to produce antibodies and memory cells.

A vaccine stimulates the production of memory cells and antibodies. On re-exposure, the immune system recognises the pathogen's antigens and produces antibodies rapidly, destroying the pathogen before it causes illness.

False.

Passive immunity involves receiving antibodies from another organism (e.g. in breast milk). It is active immunity that involves the body producing its own antibodies, either naturally or through vaccination.

If a large enough proportion of the population is vaccinated, even unvaccinated individuals are protected because the pathogen cannot spread easily. This is called herd immunity.

Active immunity is when the body produces its own antibodies — either through infection or vaccination. Passive immunity is when antibodies are received from another organism, for example through breast milk.

True.

This is known as herd immunity. When most people are vaccinated, pathogens cannot spread easily through the population, reducing the risk for those who cannot receive vaccines.

Complete the table comparing types of immunity.

Cases have increased due to a drop in vaccination rates globally. Controversy about the MMR vaccine in 1998 led to significantly fewer people being vaccinated, reducing herd immunity in many populations.

False.

Vaccines contain dead or inactive forms of a pathogen. This stimulates an immune response without causing disease, allowing memory cells to form safely.

An antibiotic is a medicine, such as penicillin, that kills bacteria inside the body by disrupting bacterial processes such as cell wall production.

Antibiotics target bacterial cell processes such as cell wall production. Viruses reproduce inside the body's own host cells, making it difficult to kill them without also damaging the body's tissues.

False.

Painkillers treat the symptoms of disease but do not kill pathogens. It is antibiotics that treat the cause of bacterial infections by killing the bacteria.

Antibiotic resistance develops when random mutations in bacterial DNA give some bacteria resistance. These bacteria survive treatment and the population of resistant bacteria increases.

Antibiotic resistance occurs when strains of bacteria evolve through natural selection so that antibiotics are no longer able to kill them, making infections increasingly difficult to treat.

True.

Not completing a course of antibiotics can allow some resistant bacteria to survive, reproduce, and spread — increasing the risk of antibiotic resistance developing.

MRSA (Methicillin-resistant Staphylococcus aureus) is a strain of bacteria resistant to the antibiotic methicillin. It is a concern because it can infect wounds and is very difficult to treat with standard antibiotics.

Complete the table comparing types of medicine.

A formulation is a medicine made by mixing ingredients in carefully measured quantities. Ingredients other than the active drug — such as aspirin — may improve taste, stability, or help the medicine dissolve so it is easier to take.

False.

Antibiotics should only be prescribed for bacterial infections when necessary. Using them for viral or mild infections the immune system can clear contributes to antibiotic resistance.

Toxicity is how harmful a drug is to the body, including any harmful side effects it may cause.

True.

All new drugs must be tested for toxicity (harmful effects), efficacy (whether they work) and dose (the lowest effective amount) before use in patients.

Preclinical testing is the first stage of drug development, where a drug is tested in the laboratory using cells, tissues and live animals before any human trials begin.

The three stages of drug development are:

1. Preclinical testing — on cells, tissues and live animals in a lab

2. Whole organism testing — on animals to observe effects in a whole body

3. Clinical trials — on healthy volunteers, then patients

In a double-blind trial, some patients are given a placebo, and patients are allocated to groups randomly so that neither the doctor nor the patient knows who received the active drug.

False.

Clinical trials begin with very low doses of the drug. The dose is only increased if the drug is found to be safe, and the aim is to find the optimum (lowest effective) dose.

Peer review ensures that the results are described accurately and that the methods and conclusions are sound before the findings are published in scientific journals.

Drugs are tested for three key properties: efficacy, which checks whether the drug works; toxicity, which checks for harmful effects; and dose, which determines the lowest effective amount.

Testing on two different animals checks the drug's efficacy, toxicity and dosage in a whole living organism, helping ensure that results are consistent across different animal species before human trials begin.

Genetic modification is changing the genetic material of an organism by removing or altering existing genes, or by inserting genes from another organism.

The human insulin gene is inserted into bacteria, which are then cultivated on a large scale. The genetically modified bacteria produce human insulin that is pure and can be made reliably and cheaply.

True.

Sheep and goats can be genetically modified so that their milk contains proteins that treat diseases such as cystic fibrosis.

Genetically modified animals could provide organs for transplantation. Their tissues are modified so they are less likely to be rejected by the human immune system, which could reduce the shortage of donor organs.

Two environmental risks of using genetically modified organisms are:

1. Modified genes could spread to wild populations through breeding

2. GM organisms could outcompete natural species, reducing biodiversity

False.

Insulin produced by genetically modified bacteria is human insulin, which means it is pure and reduces the risk of immune reactions compared to insulin taken from animals.

Two ethical concerns about gene technology in medicine are:

1. Animal welfare — animals may suffer as a result of genetic modification

2. Moral or religious objections — some people believe it is wrong to interfere with the genetic makeup of living organisms

Gene technology treatments are often expensive to develop and produce. High costs may limit access to wealthier countries or patients, potentially increasing inequality in healthcare.

Embryonic stem cells are undifferentiated cells taken from the inner cell mass of an embryo a few days old. They can develop into any type of specialised cell found in the body.

Adult stem cells have a limited ability to differentiate — they can only produce the types of cells found in the tissue they come from. Embryonic stem cells can develop into any type of specialised cell in the body.

Fetal stem cells are taken from the blood of the umbilical cord. They have a limited ability to differentiate and can produce blood cells as well as some muscle and nerve cells.

False.

Bone marrow transplants use adult stem cells, not embryonic stem cells. The transplanted stem cells differentiate into healthy blood cells, helping restore normal blood and immune system function in patients with leukaemia.

Two experimental stem cell treatments under investigation are:

1. Type 1 diabetes — stem cells differentiated into insulin-producing cells; source: embryonic or fetal stem cells

2. Heart disease — stem cells differentiated into heart muscle cells; source: the patient's own bone marrow stem cells

True.

Using a patient's own stem cells means the new cells are genetically identical to the patient's existing cells, so the immune system will not recognise them as foreign and will not reject them.

Stem cells have a high ability to divide and proliferate. If differentiation is not properly controlled, cells may continue dividing and form a tumour, raising the risk of cancer in the patient.

For: Embryonic stem cells can develop into any cell type, offering the potential to treat a wide range of diseases and save many lives.

Against: Embryos are destroyed to obtain the cells, raising questions about whether an embryo has the right to be treated as a person with human rights.

When evaluating stem cell use, you must weigh up both benefits (such as treating disease) and risks or ethical concerns (such as cancer risk or use of embryos).

A defect in the immune system means the body is less able to fight pathogens, making the individual more likely to suffer from infectious diseases such as pneumonia.

True.

Viruses that live inside cells can trigger cancers. For example, the HPV virus can lead to cervical cancer, and some strains of the hepatitis virus can cause liver cancer.

An overactive immune response occurs when the immune system reacts too strongly to a trigger, such as a pathogen. This can lead to allergies such as skin rashes and asthma.

Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma. These often develop as a result of an overactive immune response.

True.

Severe physical ill health can lead to depression and other mental illness, showing that different types of disease can interact and negatively affect overall health.

HIV eventually causes a reduction in lymphocytes in the body, which weakens the immune system. This makes individuals more vulnerable to opportunistic infections such as pneumonia, showing how one disease can increase the risk of another.

Four ways diseases can interact are:

1. Immune defects increase the risk of infectious diseases

2. Viruses in cells can trigger cancers

3. Immune reactions caused by pathogens can trigger allergies (e.g. asthma, skin rashes)

4. Severe physical ill health can lead to depression and other mental illness

False.

Allergies such as asthma and skin rashes can develop as a result of an immune reaction that was initially triggered by a pathogen — they are not always independent of infection.