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Resources Structure

Key Stage 3

Mathematics

(3131)

Science

(1890)

Key Stage 4

Biology (3261)	Chemistry (2845)
Mathematics (3791)	Physics (2806)

A level

Biology (3393)	Chemistry (3292)
Mathematics (3049)	Physics (3275)

Exam Specifications

Key Stage 4

AQA GCSE Science A (4461) Biology (3285)
AQA GCSE Additional Science (4463) Biology (3276)
AQA GCSE Biology (4411) (3305)
AQA GCSE Science A (4461) Chemistry (2845)
AQA GCSE Additional Science (4463) Chemistry (2845)
AQA GCSE Chemistry (4421) (2845)
AQA GCSE Science A (4461) Physics (2806)
AQA GCSE Physics (4451) (2806)
AQA GCSE Physics (4451) (2806)
AQA GCSE Mathematics A (4301) (3817)

A Level

AQA GCE AS/A Biology A (5411/6411 / 5413/6413) (3444)
AQA GCE AS/A Chemistry (5421/6421) (3296)
AQA GCE AS/A Physics A (5451/6451) (3275)
AQA GCE AS/A Physics B (5456/6456) (3275)
AQA GCE AS/A Mathematics (6360) (3052)

Programmes of Study

Key Stage 3

Programme of Study for Key Stage 3 Mathematics (3183)
Programme of Study for Key Stage 3 Science (1938)

Categories

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Level

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II. Biology 1 (1570)

1.How do human bodies respond to changes inside them and to their environment? (409)

to evaluate the benefits of, and the problems that may arise from, the use of hormones to control fertility, including IVF (24)

to evaluate the claims of manufacturers about sports drinks. (67)

The nervous system enables humans to react to their surroundings and coordinate their behaviour. (50)

Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature. (The structure and functions of sense organs such as the eye and the ear are not required.) (29)

Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response. (27)

Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurones. (51)

The role of receptors, sensory neurones, motor neurones, relay neurones, synapses and effectors in simple reflex actions. (50)

Internal conditions which are controlled include: - the water content of the body, - the ion content of the body, - temperature, - blood sugar levels. (160)

Many processes within the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are transported to their target organs by the bloodstream. (28)

Hormones regulate the functions of many organs and cells. E.g., the monthly release of an egg from a woman’s ovaries and the changes in the thickness of the lining of her womb are controlled by hormones secreted by: the pituitary gland and the ovaries (52)

Several hormones are involved in the menstrual cycle of a woman. Those hormones involved in promoting the release of an egg include: FSH and Oestrogen. (92)

The uses of hormones in controlling fertility include: - giving oral contraceptives which contain hormones to inhibit FSH production, - giving FSH as a ‘fertility drug’ to a woman whose level of FSH is too low (stimulate eggs to mature). (52)

2. What can we do to keep our bodies healthy? (128)

to evaluate information about the effect of food on health (58)

to evaluate claims made by slimming programmes. (31)

A healthy diet contains the right balance of the different foods you need and the right amount of energy. A person is malnourished if their diet is not balanced. This may lead to a person being too fat, too thin and to deficiency diseases. (31)

The rate at which all the chemical reactions in the cells of the body are carried out (the metabolic rate) varies with the amount of activity you do and the proportion of muscle to fat in your body. It may be affected by inherited factors. (28)

The less exercise you take and the warmer it is, the less food you need. People who exercise regularly are usually fitter than people who take little exercise. If you exercise your metabolic rate stays high for some time after you have finished. (36)

In the developed world too much food and too little exercise are leading to high levels of obesity and the diseases linked to excess weight: - arthritis (worn joints) - diabetes (high blood sugar) - high blood pressure - heart disease. (63)

Some people in the developing world suffer from health problems linked to lack of food. These include: - reduced resistance to infection - irregular periods in women. (31)

Cholesterol is a substance made by the liver and found in the blood. The amount of cholesterol produced by the liver depends on a combination of diet and inherited factors. High levels of cholesterol in the blood increase the risk of heart disease.

Cholesterol is carried around the body by two types of lipoproteins. Low-density lipoproteins (LDLs) are ‘bad’ cholesterol and can cause heart disease. High-density lipoproteins (HDLs) are ‘good’ cholesterol. The balance of these is very important.

Saturated fats increase blood cholesterol levels. Mono-unsaturated and polyunsaturated fats may help both to reduce blood cholesterol levels and to improve the balance between LDLs and HDLs.

Too much salt in the diet can lead to increased blood pressure for about 30% of the population. (27)

Processed food often contains a high proportion of fat and/or salt.

3. How do we use/abuse medical and recreational drugs? (42)

to evaluate the effect of statins on cardio-vascular disease

to evaluate the different types of drugs and why some people use illegal drugs for recreation (36)

to evaluate claims made about the effect of cannabis on health and the link between cannabis and addiction to hard drugs (36)

to explain how the link between smoking tobacco and lung cancer gradually became accepted (36)

to evaluate the different ways of trying to stop smoking.

Drugs can be beneficial but may harm the body.

Many drugs derived from natural substances have been known to indigenous peoples for many years.

Scientists are developing new drugs. These need to be thoroughly tested.

When new medical drugs are devised, they have to be extensively tested and trialled before being used. Drugs are tested in the laboratory to find if they are toxic. They are then trialled on human volunteers to iscover any side effects.

Thalidomide is a drug that was developed as a sleeping pill. It was found to be effective in relieving sickness in pregnant women. Many babies born to mothers who took the drug were born with limb abnormalities. Recently it is being used to treat leprosy.

Some people use drugs recreationally. Some of these recreational drugs are more harmful than others. Some of these drugs are legal, some illegal. (36)

The overall impact of legal drugs on health is much greater than the impact of illegal drugs, because far more people use them. (36)

Drugs change the chemical processes in people’s bodies so that they may become dependent or addicted to them and suffer withdrawal symptoms without them. Heroin and cocaine are very addictive. (36)

Nicotine is the addictive substance in tobacco smoke. Tobacco smoke contains carcinogens. (36)

Tobacco smoke also contains carbon monoxide which reduces the oxygen-carrying capacity of the blood. In pregnant women this can deprive a fetus of oxygen and lead to a low birth mass. (36)

Alcohol affects the nervous system by slowing down reactions and helps people relax, but too much may lead to lack of self-control, unconsciousness or even coma, eventually damaging the liver and brain. (36)

4. What causes infectious diseases and how can our bodies defend themselves against them? (228)

to relate the contribution of Semmelweiss in controlling infection to solving modern problems with the spread of infection in hospitals

to evaluate the advantages and disadvantages of being vaccinated against a particular disease (25)

to explain how the treatment of disease has changed as a result of increased understanding of the action of antibiotics and immunity

to evaluate the consequences of mutations of bacteria and viruses in relation to epidemics and pandemics eg bird influenza. (100)

Microorganisms that cause infectious disease are called pathogens. (33)

Bacteria and viruses may reproduce rapidly inside the body and may produce poisons (toxins) which make us feel ill. Viruses damage cells in which they reproduce. (81)

The body has different ways of protecting itself against pathogens. White blood cells help to defend against pathogens. (33)

Some medicines, including painkillers, help to relieve the symptoms of infectious disease, but do not kill the pathogens.

Antibiotics are medicines that help to cure bacterial disease by killing infective bacteria inside the body. Antibiotics cannot be used to kill viral pathogens. It is difficult to develop drugs which kill viruses without also damaging the body’s tissues. (31)

Many strains of bacteria, including MRSA, have developed resistance to antibiotics as a result of natural selection. To prevent further resistance arising it is important to avoid over-use of antibiotics. (31)

People can be immunised against a disease by introducing small quantities of dead or inactive forms of the pathogen into the body. Vaccines stimulate the white blood cells to produce antibodies that destroy the pathogens (e.g. MMR vaccine). (25)

5. What determines where particular species live and how many of them there are? (389)

to suggest how organisms are adapted to the conditions in which they live (96)

to suggest the factors for which organisms are competing in a given habitat (154)

to suggest reasons for the distribution of animals or plants in a particular habitat. (125)

To survive, organisms require a supply of materials from their surroundings and from the other living organisms there. (173)

Plants often compete with each other for light and for water and nutrients from the soil. (32)

Animals often compete with each other for food, mates and territory. (120)

Organisms have features (adaptations) which enable them to survive in the conditions in which they normally live. (91)

Animals and plants may be adapted for survival in the conditions where they normally live eg deserts, the Arctic. (134)

Animals and plants may be adapted to cope with specific features of their environment eg thorns, poisons and warning colours to deter predators. (61)

6. Why are individuals of the same species different from each other? What new methods do we have for producing plants and animals with the characteristics we prefer? (218)

to interpret information about cloning techniques and genetic engineering techniques (63)

to make informed judgements about the economic, social and ethical issues concerning cloning and genetic engineering, including GM crops. (35)

The information that results in plants and animals having similar characteristics to their parents is carried by genes which are passed on in the sex cells (gametes) from which the offspring develop. (60)

Different genes control the development of different characteristics. (32)

The nucleus of a cell contains chromosomes. Chromosomes carry genes that control the characteristics of the body. (60)

There are two forms of reproduction: - sexual reproduction, - asexual reproduction. (28)

New plants can be produced quickly and cheaply by taking cuttings from older plants. These new plants are genetically identical to the parent plant. (28)

Modern cloning techniques include: - tissue culture, - embryo transplants, - fusion cell and adult cell cloning. (35)

In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms. (63)

Genes can also be transferred to the cells of animals or plants at an early stage in their development so that they develop with desired characteristics. (35)

7. Why have some species of plants and animals died out? How do new species of plantsand animals develop? (143)

to suggest reasons why scientists cannot be certain about how life began on Earth (28)

to interpret evidence relating to evolutionary theory (25)

to suggest reasons why Darwin’s theory of natural selection was only gradually accepted (25)

to identify the differences between Darwin’s theory of evolution and conflicting theories (44)

to suggest reasons for the different theories. (5)

Fossils provide evidence of how much (or how little) different organisms have changed since life developed on Earth. (64)

The theory of evolution states that all species of living things have evolved from simple life-forms which first developed more than three billion years ago. (36)

Studying the similarities and differences between species helps us to understand evolutionary and ecological relationships. (28)

Extinction may be caused by: - changes to the environment - new predators - new diseases - new competitors. (36)

Evolution occurs via natural selection: - individual organisms may show differences in their genes, - individuals with characteristics suited to the environmen are more likely to survive, - the individual genes are passed on to the next generation. (25)

Where new forms of a gene result from mutation there may be more rapid change in a species. (54)

8. How do humans affect the environment? (189)

to analyse and interpret scientific data concerning environmental issues (101)

to weigh evidence and form balanced judgements about some of the major environmental issues facing society, including the importance of sustainable development (53)

to evaluate methods used to collect environmental data and consider their validity and reliability as evidence for environmental change. (58)

Rapid growth in the human population and an increase in the standard of living means that: - raw materials, are rapidly being used up - more waste is produced - pollution will be caused. (125)

Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste. (29)

More waste is being produced which, unless properly handled, may pollute: - water, - air, - land. (64)

Living organisms can be used as indicators of pollution: - lichens can be used as air pollution indicators - invertebrate animals can be used as water pollution indicators. (64)

Large scale deforestation in tropical areas has: - increased the release of carbon dioxide into the atmosphere, - reduced the rate at which carbon dioxide is removed from the atmosphere and ‘locked-up’ for many years as wood.

Loss of forest leads to reduction in biodiversity. Some of the organisms that are lost may have been of future use. (29)

Increases in the numbers of cattle and rice fields have increased the amount of methane released into the atmosphere. (34)

Carbon dioxide and methane in the atmosphere absorb most of the energy radiated by the Earth. Some of this energy is re-radiated back to the Earth and so keeps the Earth warmer. Increasing levels of these gases may be causing global warming. (34)

Improving the quality of life without compromising future generations is known as sustainable development. Planning is needed at local, regional and global levels to manage sustainability. (29)

III.Biology 2 (1059)

1. What are animals and plants built from? (164)

to relate the structure of different types of cells to their function in a tissue or an organ. (86)

Most human cells like most other animal cells have the following parts: - a nucleus, - cytoplasm, - a cell membrane, - mitochondria, - ribosomes. (34)

Plant cells also have a cell wall which strengthens the cell. Plant cells often have: - chloroplasts which absorb light energy to make food - a permanent vacuole filled with cell sap. (34)

The chemical reactions inside cells are controlled by enzymes. (39)

Cells may be specialised to carry out a particular function. (29)

2. How do dissolved substances get into and out of cells? (125)

Dissolved substances can move into and out of cells by diffusion and osmosis. (75)

Diffusion is the spreading of the particles of a gas resulting in a net movement from a region where they are of a higher concentration. The greater the difference in concentration, the faster the rate of diffusion. (46)

Water often moves across boundaries by osmosis. Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules. (121)

Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis. (46)

3. How do plants obtain the food they need to live and grow? (90)

to interpret data showing how factors affect the rate of photosynthesis and evaluate the benefits of artificially manipulating the environment in which plants are grown. (32)

Photosynthesis is summarised by the equation: carbon dioxide + water (+ light energy) -› glucose + oxygen (29)

During photosynthesis: - light energy is absorbed by a green substance called chlorophyll, - this energy is used by converting carbon dioxide and water into sugar, - oxygen is released as a by-product. (29)

The rate of photosynthesis may be limited by: - low temperature - shortage of carbon dioxide - shortage of light. (29)

Light, temperature and the availability of carbon dioxide interact and in practice any one of them may be the factor that limits photosynthesis. (29)

The glucose produced in photosynthesis may be converted into insoluble starch for storage. Plant cells use some of the glucose produced during photosynthesis for respiration.

Plant roots absorb mineral salts including nitrates needed for healthy growth. For healthy growth plants need mineral ions including: - nitrate, - magnesium. (29)

The symptoms shown by plants growing in conditions where mineral ions are deficient include: - stunted growth if nitrate ions are deficient - yellow leaves if magnesium ions are deficient. (29)

4. What happens to energy and biomass at each stage in a food chain? (23)

to interpret pyramids of biomass and construct them from appropriate information (23)

to evaluate the positive and negative effects of managing food production and distribution, and to be able to recognise that practical solutions to human needs may require compromise between competing priorities.

Radiation from the Sun is the source of energy for most communities of living organisms. Green plants capture a small part of the solar energy which reaches them. This energy is stored in the substances which make up the cells of the plants. (23)

The mass of living material (biomass) at each stage in a food chain is less than it was at the previous stage. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass. (23)

At each stage in a food chain, less material and less energy are contained in the biomass of the organisms. This means that the efficiency of food production can be improved by reducing the number of stages in food chains. (23)

The efficiency of food production can also be improved by restricting energy loss from food animals by limiting their movement and by controlling the temperature of their surroundings.

The amounts of material and energy contained in the biomass of organisms is reduced at each successive stage in a food chain.

5. What happens to the waste material produced by plants and animals? (66)

Living things remove materials from the environment for growth and other processes. These materials are returned to the environment either in waste materials or when living things die and decay. (32)

Materials decay because they are broken down (digested) by micro-organisms. Microorganisms digest materials faster in warm, moist conditions. Many microorganisms are also more active when there is plenty of oxygen. (34)

The decay process releases substances which plants need to grow. (34)

In a stable community, the processes which remove materials are balanced by processes which return materials. The materials are constantly cycled. (34)

The constant cycling of carbon is called the carbon cycle (explain why).

6. What are enzymes and what are some of their functions? (173)

to evaluate the advantages and disadvantages of using enzymes in home and industry. (32)

Catalysts increase the rate of chemical reactions. Biological catalysts are called enzymes. (39)

Enzymes are protein molecules made up of long chains of amino acids. These long chains are folded to produce a special shape. This shape is vital for the enzyme’s function. High temperatures destroy this shape. Enzymes work best at different pH values. (39)

Enzymes inside living cells catalyse processes such as respiration, protein synthesis and photosynthesis. (39)

During aerobic respiration (respiration which uses oxygen) chemical reactions occur which: – use glucose (a sugar) and oxygen – release energy. (28)

Most of the reactions in aerobic respiration take place inside mitochondria. (28)

Aerobic respiration is summarised by the equation: glucose + oxygen -› carbon dioxide + water (+ energy) (28)

The energy that is released during respiration is used: - to build up larger molecules using smaller ones, - in animals, - in mammals and birds, - in plants. (28)

Enzymes inside living cells catalyse the reactions that build up amino acids and proteins. (86)

Digestive enzymes are produced by specialised cells in glands and in the lining of the gut. The enzymes then pass out of the cells into the gut where they come into contact with food molecules. They catalyse the breakdown of large molecules into smaller.

Some microorganisms produce enzymes which pass out of the cells. These enzymes have many uses in the home and in industry. (32)

In the home, biological detergents may contain protein-digesting and fat-digesting enzymes (proteases and lipases). (59)

In industry: - proteases are used to ‘pre-digest’ the protein in some baby foods - carbohydrases are used to convert starch into sugar syrup - isomerase is used to convert glucose syrup into fructose syrup. (32)

7. How do our bodies keep internal conditions constant? (143)

to evaluate the data from the experiments by Banting and Best which led to the discovery of insulin

to evaluate modern methods of treating diabetes.

Waste products which have to be removed from the body include: - carbon dioxide produced by respiration, - urea produced in the liver by the breakdown of excess amino acids. (51)

Internal conditions which are controlled include the water content of the body, the ion content of the body, temperature and blood sugar levels. (89)

If the water or ion content of the body is wrong, too much water may move into or out of the cells and damage them. Water and ions enter the body when we eat and drink. (89)

Sweating helps to cool the body. More water is lost when it is hot, and more water has to be taken as drink or in food to balance this loss. (82)

Body temperature is monitored by the thermoregulatory centre in the brain. It has receptors sensitive to the temperature of blood flowing through the brain. Also temperature receptors in the skin send impulses giving information about skin temperature. (31)

If the core body temperature is too high: - blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost - sweat glands release more sweat which cools the body as it evaporates. (31)

If the core body temperature is too low: - blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries, - muscles may ‘shiver’. (31)

The blood glucose concentration of the body is monitored and controlled by the pancreas. The pancreas produces the hormone insulin which allows glucose to move from the blood into the cells. (61)

Diabetes is a disease in which a person’s blood glucose concentration may rise to a fatally high level because the pancreasdoes not produce enough of the hormone insulin (treated by careful attention to diet and by injecting insulin into the body).

8. Which human characteristics show a simple pattern of inheritance? (390)

to explain why Mendel proposed the idea of separately inherited factors and why the importance of this discovery was not recognised until after his death (28)

to interpret genetic diagrams (28)

to make informed judgements about the social and ethical issues concerning the use of stem cells from embryos in medical research and treatments

to make informed judgements about the economic, social and ethical issues concerning embryo screening that they have studied or from information that is presented to them (35)

to predict and/or explain the outcome of crosses between individuals for each possible combination of dominant and recessive alleles of the same gene (49)

to construct genetic diagrams. (28)

In body cells the chromosomes are normally found in pairs. Body cells divide by mitosis to produce additional cells during growth or to produce replacement cells. Body cells have two sets f genetic information; sex cells (gametes) have only one set. (59)

Cells in reproductive organs – testes and ovaries in humans - divide to form gametes. (26)

The type of cell division in which a cell divides to form gametes is called meiosis. When a cell divides to form gametes: - copies of the chromosomes are made - then the cell divides twice to form four gametes, each with a single set of chromosomes. (77)

When gametes join at fertilisation, a single body cell with new pairs of chromosomes is formed. A new ndividual then develops by this cell repeatedly dividing by mitosis. (101)

Most types of animal cells differentiate at an early stage. Plant cells retain the ability to differentiate throughout life. In mature animals, cell division is restricted to repair and replacement. (29)

The cells of the offspring produced by asexual reproduction are produced by mitosis from the parental cells. They contain the same genes as the parents.

Sexual reproduction gives rise to variation because, when gametes fuse, one of each pair of alleles comes from each parent. (28)

In human body cells, one of the 23 pairs of chromosomes carries the genes which determine sex. In females the sex chromosomes are the same (XX) in males the sex chromosomes are different (XY).

Some characteristics are controlled by a single gene. Each gene may have different forms called alleles.

An allele which controls the development of a characteristic when it is present on only one of the chromosomes is a dominant allele.

An allele which controls the development of characteristics only if the dominant allele is not present is a recessive allele.

Chromosomes are made up of large molecules of DNA (deoxyribose nucleic acid). A gene is a small section of DNA. (26)

Each gene codes for a particular combination of amino acids which make a specific protein. (52)

Each person (apart from identical twins) has unique DNA. This can be used to identify individuals in a process known as DNA fingerprinting. (7)

Some disorders are inherited: - Huntington’s disease, - cystic fibrosis. (60)

Embryos can be screened for the alleles that cause these and other genetic disorders. (1)

III.Biology 3 (699)

1. How do dissolved materials get into and out of animals and plants? (268)

to explain how gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness. (1)

Dissolved substances move by diffusion. (47)

Substances are sometimes absorbed against a concentration gradient. This requires the use of energy from respiration (active transport). It enables cells to absorb ions from very dilute solutions. (47)

Many organ systems are specialised for exchanging materials.

In humans: - the surface area of the lungs is increased by the alveoli - and that of the small intestine by villi. (34)

The lungs are in the upper part of the body (thorax) protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm. (34)

The breathing system takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air. (34)

The alveoli provide a very large, moist surface, richly supplied with blood capillaries so that gases can readily diffuse into and out of the blood. (34)

The villi provide a large surface area with an extensive network of capillaries to absorb the products of digestion by diffusion and active transport. (52)

In plants: – carbon dioxide enters leaf cells by diffusion – most of the water and mineral ions are absorbed by root hair cells.

The surface area of the roots is increased by root hairs and the surface area of leaves by the flattened shape and internal air spaces. (132)

Plants have stomata to obtain carbon dioxide from the atmosphere. (100)

Plants lose water vapour from the surface of their leaves (transpiration). Most of the transpiration is through stomata. If plants lose water faster than it is replaced by the roots, the stomata can close to prevent wilting. (75)

2. How are dissolved materials transported around the body? (97)

Blood flows to the organs through arteries and returns through veins. Substances needed by cells in the body tissues pass out of the blood. Substances produced by the cells pass into the blood through the walls of the capillaries. (56)

There are two separate circulation systems, one to the lungs and one to all the other organs of the body. (28)

Blood plasma transports: - carbon dioxide from the organs to the lungs - soluble products of digestion from the small intestine to other organs - urea from the liver to the kidneys. (36)

Red blood cells transport oxygen from the lungs to the organs. Red blood cells have no nucleus. They are packed with a red pigment called haemoglobin. In the lungs haemoglobin combines with oxygen to form oxyhaemoglobin. (36)

3. How does exercise affect the exchanges taking place within the body? (91)

to interpret data relating to the effects of exercise on the human body. (36)

The energy that is released during respiration is used to enable muscles to contract. (27)

During exercise a number of changes take place: - the heart rate increases - rate and depth of breathing increases - the arteries supplying the muscles dilate. (36)

These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide.

Glycogen stores in the muscle are used during exercise. (63)

If muscles are subjected to long periods of vigorous activity they become fatigued, ie they stop contracting efficiently. If insufficient oxygen is reaching the muscles they use anaerobic respiration to obtain energy. (64)

Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid. As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. (64)

4. How do exchanges in the kidney help us to maintain the internal environment in mammals and how has biology helped us to treat kidney disease? (51)

to evaluate the advantages and disadvantages of treating kidney failure by dialysis or kidney transplant. (51)

A healthy kidney produces urine by: - first filtering the blood - reabsorbing all the sugar - reabsorbing the dissolved ions needed by the body - reabsorbing as much water as the body needs - releasing urea, excess ions and water as urine. (51)

Sugar and dissolved ions may be actively absorbed against a concentration gradient. (51)

People who suffer from kidney failure may be treated either by using a kidney dialysis machine or by having a healthy kidney transplanted. (51)

Treatment by dialysis restores the concentrations of dissolved substances in the blood to normal levels. The dialysis fluid contains the same concentration of useful substances as the blood. (51)

A kidney transplant enables a diseased kidney to be replaced with a healthy one from a donor. However, the donor kidney may be rejected by the immune system unless precautions are taken. (51)

To prevent rejection of the transplanted kidney: - a donor kidney with a ‘tissue-type’ similar to that of the recipient is used - the recipient is treated with drugs that suppress the immune system. (51)

5. How are microorganisms used to make food and drink? (96)

to explain how scientists such as Spallanzani, Schwann and Pasteur were involved in the development of the theory of biogenesis. (28)

Microorganisms are used to make food and drink: - bacteria are used in yoghurt and cheese manufacture - yeast is used in making bread and alcoholic drinks. (68)

Yeast is a single-celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall. (35)

Yeast can respire without oxygen (anaerobic respiration), producing carbon dioxide and ethanol (alcohol). This is called fermentation. Aerobic respiration provides more energy and is necessary for the yeast to grow and reproduce. (33)

In brewing beer and wine-making, carbohydrates are used as an energy source for yeast to respire. (33)

In wine-making the yeast uses the natural sugars in the grapes as its energy source. (33)

In the production of yoghurt: - a starter of bacteria is added to warm milk - the bacteria ferment the milk sugar (lactose) producing lactic acid - the lactic acid causes the milk to clot and solidify into yoghurt. (33)

6. What other useful substances can we make using microorganisms? (96)

to interpret economic and environmental data relating to production of fuels by fermentation and their use (65)

to evaluate the advantages and disadvantages of given designs of biogas generator. (32)

Microorganisms can be grown in large vessels called fermenters to produce useful products such as antibiotics. Industrial fermenters usually have: - an air supply, - a stirrer, - a water-cooled jacket, - instruments.

The antibiotic, penicillin, is made by growing the mould Penicillium, in a fermenter. The medium contains sugar and other nutrients eg a source of nitrogen. The Penicillium only starts to make penicillin after using up most of the nutrients for growth. (31)

The fungus Fusarium is used to make mycoprotein, a protein-rich food suitable for vegetarians. The fungus is grown on starch in aerobic conditions and the biomass is harvested and purified.

Fuels can be made from natural products by fermentation. Biogas, mainly methane, can be produced by anaerobic fermentation of a wide range of plant products or waste material containing carbohydrates. (32)

On a large scale, waste from, for example, sugar factories or sewage works can be used. On a small scale, biogas generators can be used to supply the energy needs of individual families or farms. (32)

Ethanol-based fuels can be produced by the anaerobic fermentation of sugar cane juices and from glucose derived from maize starch by the action of carbohydrase. The ethanol is distilled from the products of the fermentation.

7. How can we be sure we are using microorganisms safely? (33)

Microorganisms can be grown in a culture medium containing carbohydrates as an energy source, mineral ions, and in some cases supplementary protein and vitamins. These nutrients are often contained in an agar medium. (33)

In order to prepare useful products, uncontaminated cultures of microorganism are required. (33)

In school, cultures should be incubated at a maximum temperature of 25°C which greatly reduces the likelihood of pathogens growing (harmful to humans). In industrial conditions higher temperatures can produce more rapid growth. (33)

IV.Biology (779)

1. Additional materials (779)

Additional materials (779)

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Ethanol-based fuels can be produced by the anaerobic fermentation of sugar cane juices and from glucose derived from maize starch by the action of carbohydrase. The ethanol is distilled from the products of the fermentation. -
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