GCSE Science₈₄₆₅

Describe the relationship between health and disease.

Describe different types of diseases (including communicable and non-communicable diseases).

Health can be defined as 'a state of physical, mental and social well-being' and not merely the absence of disease. Factors including diet, stress and life situations can affect both physical and mental health.

Diseases stop part of the body from working properly. This causes symptoms, which are experienced by the person affected by the disease.

Communicable (infectious) diseases are caused by microorganisms called pathogens. They may infect plants as well as animals and are spread by direct contact, by water or by air.

Non-communicable diseases, such as heart disease, cancer and diabetes, are the leading cause of death in the world.

Recall that many non-communicable human diseases are caused by the interaction of a number of factors. To include cardiovascular diseases, many forms of cancer, some lung and liver diseases and diseases influenced by nutrition, including Type 2 diabetes.

Explain the effect of lifestyle factors, including exercise, diet, alcohol and smoking, on the incidence of non-communicable diseases at local, national and global levels.

Risk factors are aspects of a person’s lifestyle, or substances present in a person’s body or environment, that have been shown to be linked to an increased rate of a disease. For some a causal mechanism has been proven.

Examples are:

• the effects of diet, smoking and exercise on cardiovascular disease
• obesity as a risk factor for Type 2 diabetes
• the effect of alcohol on liver and brain function
• the effect of smoking on lung disease and lung cancer
• the effects of smoking and alcohol on unborn babies
• carcinogens and ionising radiation as risk factors in cancer.

WS 1.5

Interpret data about risk factors, or about differences in the incidence of non-communicable diseases in different parts of the world.

WS 1.4

Discuss the human and financial cost of these non-communicable diseases to an individual, a local community, a nation or globally.

MS 4a

Translate information between graphical and numerical forms.

MS 2c, 4a

Extract and interpret information from charts, graphs and tables.

MS 2d

Understand the principles of sampling as applied to scientific data in terms of risk factors.

MS 2c

Construct and interpret frequency tables and diagrams, bar charts and histograms.

MS 2g

Use a scatter diagram to identify a correlation between two variables.

Evaluate some different treatments for cardiovascular disease.

In coronary heart disease layers of fatty material build up inside the coronary arteries. This reduces the flow of blood through the coronary arteries. This can lead to a heart attack.

Statins are widely used to reduce blood cholesterol levels, which slows down the rate of fatty material deposit.

Stents are used to keep the coronary arteries open.

In some people heart valves may become faulty, preventing the valve from opening fully, or the heart valve might develop a leak.

Faulty heart valves can be replaced using biological or mechanical valves.

In the case of heart failure, a donor heart, or heart and lungs, can be transplanted. Artificial hearts are occasionally used to keep patients alive whilst waiting for a heart transplant, or to allow the heart to rest as an aid to recovery.

WS 1.4

Evaluate given information about the advantages and disadvantages of treating cardiovascular diseases by drugs, mechanical devices or transplant.

WS 1.3

Evaluate methods of treatment bearing in mind the benefits and risks associated with the treatment.

Explain the importance of maintaining a constant internal environment in response to internal and external change.

Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes. Homeostasis is important because it maintains optimal conditions for enzyme action and all cell functions.

Control of blood glucose concentration, control of body temperature and control of water levels in the human body are examples of homeostasis.

An organism maintains homeostasis by monitoring its internal conditions and responding appropriately when these conditions deviate from their optimal state.

These automatic control systems may involve nervous responses or chemical responses. Many of the processes are coordinated by hormones.

Explain how insulin controls blood sugar levels in the body.

(HT only) Explain how glucagon interacts with insulin to control blood sugar levels in the body.

Blood glucose concentration is monitored and controlled by the pancreas.

If the blood glucose concentration is too high, the pancreas produces the hormone insulin, which causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage.

(HT only) If the blood glucose concentration is too low, the pancreas produces glucagon, which causes glycogen to be converted into glucose and released into the blood.

MS 1a, 1c, 2c, 4a, 4c

Translate information between numerical and graphical forms and extract and interpret information from graphs, charts and tables.

Compare Type 1 and Type 2 diabetes and explain how they can be treated.

Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.

In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas. A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes.

Describe the roles of hormones in human reproduction, including the menstrual cycle.

(HT only) Explain the interactions of FSH, LH, oestrogen and progesterone in the control of the menstrual cycle.

During puberty reproductive hormones cause secondary sex characteristics to develop. Oestrogen is the main female reproductive hormone produced in the ovary. At puberty eggs begin to mature and one is released approximately every 28 days. This is called ovulation. Testosterone is the main male reproductive hormone produced by the testes and it stimulates sperm production.

Several hormones are involved in the menstrual cycle of a woman.

• Follicle-stimulating hormone (FSH) causes maturation of an egg in the ovary.
• Luteinising hormone (LH) stimulates the release of the egg.
• Oestrogen and progesterone are involved in maintaining the uterus lining.

MS 2c, 4a

(HT only) Extract and interpret data from graphs showing hormone levels during the menstrual cycle.

Explain the use of hormones in contraception and evaluate hormonal and non-hormonal methods of contraception.

Fertility can be controlled by a variety of hormonal and non-hormonal methods of contraception. These include:

• oral contraceptives that contain hormones
• injection, implant or skin patch of slow-release progesterone
• barrier methods such as condoms and diaphragms
• intrauterine devices
• spermicidal agents
• abstaining from intercourse at times when an egg may be fertilised
• surgical methods of male and female sterilisation.

WS 1.4

Explain everyday and technological applications of science; evaluate associated personal, social, economic and environmental implications; and make decisions based on the evaluation of evidence and arguments.

Explain the use of hormones in modern reproductive technologies to treat infertility.

The uses of hormones in controlling fertility include:

• giving FSH and LH in a 'fertility drug' to a woman whose own level of FSH is too low
• In Vitro Fertilisation (IVF) treatment, which involves giving a mother FSH and LH to stimulate the maturation of several eggs.

WS 1.4

Evaluate, from the perspective of patients and doctors, the methods of treating fertility bearing in mind that although fertility treatment gives couples the chance to have a baby of their own it is very emotionally and physically stressful; the success rates are not high and it can lead to multiple births which are a risk to both the babies and the mother.

Recall that the arrangements of electrons in atoms may change with absorption or emission of electromagnetic radiation.

When atoms gain energy by heating, from electricity, or by absorbing electromagnetic radiation, some electrons jump to higher energy levels. Electromagnetic radiation is given out when the electrons drop back to lower levels.

The frequency of the radiation depends on the size of the energy jump. Atoms of elements such as neon and sodium give out light in the visible region of the spectrum. Other atoms, such as mercury atoms, give out light in the ultraviolet region.

WS 1.2

Use of the energy level model of the atom.

Recall that some nuclei are unstable and may emit alpha particles, beta particles, or neutrons, and electromagnetic radiation as gamma rays; relate these emissions to possible changes in the mass or the charge of the nucleus, or both.

Use names and symbols of common nuclei and particles to write balanced equations that represent radioactive decay.

The nuclear radiation emitted may be:

• an alpha particle (α) – this consists of two neutrons and two protons; it is identical to the nucleus of a helium atom
• a beta particle (β) – a high-speed electron ejected from the nucleus as a neutron turns into a proton
• a gamma ray (γ) – electromagnetic radiation from the nucleus
• a neutron (n).

Nuclear equations are used to represent radioactive decay.

In a nuclear equation an alpha particle may be represented by the symbol:

and a beta particle by the symbol:

The emission of the different types of ionising radiation may cause a change in the mass and/or the charge of the nucleus. For example, alpha decay causes the atomic number to decrease by two units and the mass number by four units:

There is no change in mass number during beta decay but the atomic number increases by one unit.

Students are not required to recall these two examples.

The emission of a gamma ray does not cause the mass or the charge of the nucleus to change.

WS 1.2, MS 1b, 1c, 3c

Refer to a copy of the periodic table and use the names and symbols of common nuclei and particles to write balanced equations that show single alpha (α) and beta (β) decay. This includes balancing atomic numbers and mass numbers.

Explain the concept of half-life and how this is related to the random nature of radioactive decay.

Radioactive decay is random, so it is not possible to predict which individual nucleus will decay next. But with a large enough number of nuclei it is possible to predict how many will decay in a certain amount of time.

The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve, or the average time it takes for the count rate from a sample containing a radioactive isotope to fall to half its initial level.

Count rate is the number of decays recorded each second by a detector (such as a Geiger–Müller tube).

WS 3.3

Carry out and represent mathematical and statistical analysis.

MS 4a

Determine the half-life of a radioactive isotope from given information.

MS 1c, 3d

(HT only) Calculate the net decline, expressed as a ratio, in a radioactive emission after a given number of half-lives.

Recall the differences in the penetration properties of alpha particles, beta particles and gamma rays.

Alpha particles are absorbed by just a few millimetres of air or by a thin sheet of paper.

Beta particles can pass through air and paper but are completely absorbed by a sheet of metal just a few millimetres thick.

Gamma rays pass through most materials easily but are absorbed by a thick sheet of lead or by several metres of concrete.

Recall the differences between contamination and irradiation effects and compare the hazards associated with these two.

Irradiation is the process of exposing an object to radiation from an outside source. Irradiation can be reduced by screening the source or moving the object away from it. The irradiated object does not become radioactive.

Radioactive contamination is the unwanted presence of a source of radiation inside, or on the surface of, other materials. It is often difficult to remove the contaminating source so that it continues to add to the radiation dose for as long as it emits radiation.

Recall that changes in atoms and nuclei can also generate and absorb radiations over a wide frequency range.

Describe how ultraviolet waves, X-rays and gamma rays can have hazardous effects, notably on human bodily tissues.

Recall that atoms can become ions by loss of outer electrons.

The hazardous effects of ultraviolet (UV) waves, X-rays, alpha, beta and gamma rays depend on the type of radiation and the size of the dose.

Radiation dose (in Sieverts) is a measure of the risk of harm resulting from an exposure of the body to the radiation. 1 Sievert (Sv) = 1000 millisieverts (mSv).

Ultraviolet waves, X-rays, alpha, beta and gamma rays are all examples of ionising radiation. They can turn atoms into ions and break up molecules. Ionising radiations can change DNA, causing mutation of genes that may lead to cancer. High-energy gamma rays can be used to destroy cancer cells.

WS 1.5

Interpret simple measures of risk showing the probability of harm from different types of radiation.

Describe precautions that can be taken to reduce the risks from ionising radiation.

Give examples to show that the perceived risk can be very different from the measured risk, especially if the cause of the risk is unfamiliar or invisible.

Describe cancer as the result of changes in cells that lead to uncontrolled growth and division.

Tumours form when cells start growing and dividing in an uncontrolled way. Some tumours are benign; they stay in the same place and stop growing before they get too large.

Cancer is caused by malignant tumours that are able to invade neighbouring tissues and spread to different parts of the body in the blood so that more tumours start to grow in other parts of the body.

Explain how communicable diseases (caused by viruses, bacteria, protists and fungi) are spread in animals.

Harmful microorganisms (pathogens) that cause disease can spread:

• through the air when people cough or sneeze
• through food that is contaminated with bacteria
• through drinking water that is contaminated with microorganisms
• through contact with other people, or surfaces that infected people have touched
• by animals that scratch, bite or draw blood.

WS 1.2

Apply the ideas in this section to the transmission of the common cold, flu, cholera, athlete's foot and malaria.

Describe a minimum of one common human infection, and sexually transmitted infections in humans, including HIV/AIDS.

Explain how the spread of communicable diseases may be reduced or prevented in animals. This should include a minimum of one common human infection, and sexually transmitted infections in humans including HIV/AIDS.

Salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions. Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete. Salmonella bacteria are killed by cooking and pasteurisation. In the UK, poultry are vaccinated against Salmonella to control the spread.

Measles is a viral disease showing symptoms of fever and a red skin rash. Measles is a serious illness that can be fatal if complications arise. For this reason most young children are vaccinated against measles. The measles virus is spread by inhalation of droplets from sneezes and coughs.

Gonorrhoea is a sexually transmitted disease (STD) with symptoms of a thick yellow or green discharge from the vagina or penis and pain on urinating. It is caused by a bacterium and was easily treated with the antibiotic penicillin until many resistant strains appeared. Gonorrhoea is spread by sexual contact. The spread can be controlled by treatment with antibiotics or the use of a barrier method of contraception such as a condom.

HIV initially causes a 'flu like illness'. Unless successfully treated with antiretroviral drugs the virus attacks the body’s immune cells. Late-stage HIV, or AIDS, occurs when the body’s immune system is no longer able to deal with other infections or cancers. HIV is spread by sexual contact or exchange of body fluids such as blood.

WS 1.4

Explain applications of science to prevent the spread of diseases.

Describe the non-specific defence systems of the human body against pathogens.

The human body defends itself against the entry of pathogens in the following ways:

• the skin is a barrier and produces antimicrobial secretions
• the nose catches particles
• the trachea and bronchi secrete mucus that is moved by cilia
• the stomach produces acid, which kills the majority of pathogens that enter via the mouth.

Explain the role of the immune system of the human body in defence against disease.

If a pathogen enters the body the immune system tries to destroy the pathogen. White blood cells are an important part of the immune system. They help to defend against pathogens through:

• phagocytosis
• producing antibodies
• producing antitoxins.

Explain the use of vaccines in the prevention and treatment of disease.

Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies. If the same pathogen re-enters the body the white blood cells respond quickly to produce antibodies, preventing infection.

If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced.

Students do not need to know details of vaccination schedules and side effects associated with specific vaccines.

Explain the use of medicines in the prevention and treatment of disease.

Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. It is important that specific bacteria should be treated by specific antibiotics.

The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. However, the emergence of strains of bacteria resistant to antibiotics is becoming a serious threat.

Antibiotics cannot kill viral pathogens.

Painkillers and other medicines are used to treat the symptoms of disease. They do not kill pathogens.

This topic links with Variation and evolution .

Explain that many useful materials are formulations of mixtures.

Most medicines are mixtures. They are formulations made by mixing the ingredients in carefully measured quantities to ensure that the product has the required properties. One or more of the ingredients may be the drug, such as aspirin, but other ingredients make it easier or more pleasant for a patient to take the drug in solution or as a capsule or tablet.

Describe the process of discovery and development of potential new medicines, including preclinical and clinical testing.

When new medical drugs are devised, they have to be extensively tested and trialled before being used. Drugs are tested in a series of stages to find out if they are safe and effective.

New drugs are extensively tested for toxicity, efficacy and dose:

• in the laboratory, using cells, tissues and live animals
• then in clinical trials involving healthy volunteers and patients. Very low doses of the drug are given at the start of the clinical trial. If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug.

In double-blind trials, some patients are given a placebo. Patients are allocated randomly to groups so that neither the doctors nor the patients know who has received a placebo and who has received the drug until the trial is complete.

WS 1.6

Explain that the results of testing and trials, like the findings of all scientific research, are published only after evaluation by peer review.

Explain some of the possible benefits and risks, including practical and ethical considerations, of using gene technology in modern medicine.

New medical products have been produced by genetically modifying bacteria. Insulin for the treatment of Type 1 diabetes is produced by cultivating genetically modified bacteria.

Sheep and goats have been genetically modified to produce chemicals in their milk that can be used to treat disease. In one example the milk produced contains a protein needed to treat patients with cystic fibrosis.

Research is also exploring the possibility of providing tissues needed for transplants from animals that have been genetically modified so that the tissues are not rejected by the human immune system.

WS 1.3

Evaluate gene technologies, taking into account benefits, risks , and the ethical issues raised by the use of animals in medical research.

This topic links with Variation and evolution .

Discuss potential benefits and risks associated with the use of stem cells in medicine.

One medical use of stem cells is well established: this is the use of stem cells from bone marrow in transplants to provide a supply of new blood cells for the person receiving the transplant. This is used to treat leukaemia.

Stem cells for research may be based on:

• stem cells from embryos that are a few days old
• adult stem cells from selected parts of the body such as bone marrow
• fetal stem cells taken from blood in the umbilical cord.

Embryonic stem cells can develop into any of the many types of cells in the body. Adult stem cells can only give rise to the types of cells found in the tissues that the adult stem cells come from.

Most medical uses of stem cells are still experimental. Treatments based on stem cells are being investigated for treating diseases such as:

• heart disease – using the patient’s own stem cells from bone marrow
• Type 1 diabetes – using embryo or fetal stem cells.

The properties of stem cells are not fully understood. Scientists do not yet know how their differentiation is controlled. This means that there is a fear that their ability to proliferate could lead to cancer when they are transplanted into a patient.

WS 1.3

Give a simple ethical argument about the rights and wrongs of the uses of stem cells.

Evaluate possible uses of stem cells taking into account benefits, risks and the ethical issues raised by sources of the cells.

Describe the interactions between different types of disease.

Different types of disease may interact. Some examples include:

• defects in the immune system mean that an individual is more likely to suffer from infectious diseases
• viruses living in cells can be the trigger for cancers
• immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma
• severe physical ill health can lead to depression and other mental illness.