Answers
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35B3.1 1 Functional foods
Students’ Book pages
1 A food that contains an added ingredient that promotes good health. The ingredient is not normally found in that food.
2 Prebiotics contain oligosaccharides which are food for beneficial bacteria in our gut. Probiotics contain the beneficial bacteria themselves.
3 They are food for the beneficial bacteria which live in the human gut.
4 The foods reduce the level of cholesterol in the blood. Raised cholesterol levels increase the risk of heart disease.
5 Opinions might include: the doubts expressed about the benefits claimed for functional food; that functional foods should be tested for the benefits claimed before they can be marketed as functional foods; that many of the naturally occurring ingredients of a balanced diet are those that are added to foods to make them functional.
Summary exercise
functional, prebiotics, oligosaccharides, bacteria, fermentation, cholesterol, heart disease
Higher questions
1 The health benefit claimed should be independent of all other variables (e.g. other benefits which may work together with the benefit in question). The food to be tested should be available to two groups of volunteers standardised for age, gender and metabolic functions. The volunteers in one group take in a certain mass of food containing the functional ingredient for a certain time. The same happens in the other group, except the food does not contain the functional ingredient. Each group is monitored to measure any health benefit. In practice, to control all variables other than the one under investigation (health benefit) is difficult.
2 Student’s own answer.
Extension questions
1 a kills cancer cells;
b loss of bone density (sometimes called ‘thinning of bones’);
c by undertaking clinical trials which compare the health (incidence of cancer, development of osteoporosis) of people eating prebiotics compared with people who are eating a placebo (not a prebiotic).
2 Students should read the information on the label of each food they choose. Prebiotics contain oligosaccharides which promote an increase in the numbers of ‘good’ bacteria in the gut. Probiotics contain the ‘good’ bacteria themselves.
3 Yoghurt is a probiotic food which contains some of the ‘good’ bacteria that might have been killed in the gut of a person taking antibiotics long term.
Worksheet B3.1 1a
1 Slicing increases the surface area available on which yeast enzymes can catalyse fermentation reactions. The rate of fermentation increases. Boiling kills microorganisms which interfere with the fermentation reactions.
2 a Anaerobic respiration;
b ethanol and carbon dioxide
yeast
c sugar ® ethanol + carbon dioxide
3 The components of a mixture each have different boiling points. Careful control of temperature allows each component to be boiled and vaporised separately. In each case the vapour is cooled and the distillate collected as a fraction separate from the other liquids in the mixture.
5 The liquid which distils at 78 °C and is collected.
7 No – the purity of the product is not guaranteed.
Worksheet B3.1 1b
The students’ responses should be based on definitions of the words in the reverseword.
B3.1 2 Making yoghurt and soy sauce
Students’ Book pages
1 Microorganisms breaking down large molecules to produce different substances, usually under anaerobic conditions.
2 Lactobacillus.
3 a To kill bacteria which might spoil the product;
b to mix up the ingredients;
c to promote the activity of Lactobacillus bacteria.
4 To slow the multiplication of Lactobacillus bacteria left over after the yoghurt has been made.
5 Aspergillus, Lactobacillus and yeast.
6 a To remove sediment suspended in the liquid;
b to kill bacteria which would spoil the product;
c to allow its flavours to develop.
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35B3.1 / Answers ® continued
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35
7 Diagrams should have the following steps:
a homogenisation; sterilisation; starter culture added; fermentation; raw yoghurt; cooling; flavourings (optional); packaged.
b soya beans cooked; mixed with ground, roasted wheat; Aspergillus mould added; spread on warm, shallow trays; aerated; brine added; yeasts and Lactobacillus bacteria added; raw soy sauce drained from mixture; filtration; boiling; cooling; filtration; pasteurisation; stored; bottled.
Summary exercise
lactic acid, fermentation, coagulates, lactose, cooled, natural
Higher questions
1 a Proteases;
b carbohydrases.
2 a Amino acids;
b sugars;
3 Aspergillus mould.
Extension questions
1 a The oxidation of sugar (glucose) by cells, releasing energy;
b glucose (sugar) ® alcohol (ethanol) + carbon dioxide.
2 a Aerobic respiration occurs in the presence of oxygen; anaerobic respiration occurs in the absence of oxygen;
b ethanol + oxygen ® ethanoic acid (acetic acid)
c CH3CH2OH + O2 ® CH3COOH + H2O
Worksheet B3.1 2a
3 Students should use the Internet to search for relevant information.
4 a The presence of lactic acid;
b the antibiotic kills lactic acid bacteria.
5 The starter culture contained lactic acid bacteria.
6 To ensure that microorganisms do not contaminate and spoil the product.
7 So that the events observed in container A can be compared.
Worksheet B3.1 2b
1 F A G B C H E D
2 The sauce is rich in amino acids which combine to form proteins.
3 To kill microorganisms that might contaminate the product on the surface of the beans.
4 Aspergillus.
5 Because enzymes produced by the mould digest proteins and carbohydrates.
proteases
proteins ® amino acids
carbohydrases
carbohydrates ® sugars
6 Gives soy sauce its salty taste and helps to preserve the product.
7 Lactobacillus.
8 Yeast ferments sugar at low levels of oxygen (anaerobic conditions). Mould enzymes catalyse the breakdown of proteins and carbohydrates in the mixture of cooked soya beans and ground roasted wheat.
Worksheet B3.1 2c
Across: 4 homogenised, 5 lactate, 7 lactose, 8 Aspergillus
Down: 1 Lactobacillus bulgaricus, 2 brine, 3 amino acids, 6 flavours
B3.1 3 More on microorganisms and food
Students’ Book pages
1 Rennet obtained from the stomach tissue of slaughtered calves.
2 Organisms into whose genetic material genes from a different species have been inserted.
3 Because it is not made by GM organisms even though the enzyme (chymosin) used to make it is.
4 Gelatine is made from animal bones. Vegetarians do not eat meat. Carrageen extract is made from the seaweed carrageen.
5 Monosodium glutamate. It is a flavour enhancer.
6 a Corynebacterium glutamicum;
b Acetobacter.
7 Aspergillus niger.
8 It enhances flavour and prevents the breakdown of vitamin C.
9 It is sweeter than glucose.
10 Points should include: that microorganisms are specific in their activities, so the product is not contaminated by unwanted substances; the activities of microorganisms can be controlled by alterations in temperature, pH etc.; microorganisms can be cultured in fermenters and product can be extracted from the culture.
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35B3.1 / Answers ® continued
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35
Summary exercise
protein, chymosin, cheese, gelling, carrageen, glutamic acid, invertase, fructose, yeast
Higher questions
1 Algae may be single-celled (e.g. Pleurococcus), form filaments (e.g. Spirogyra) or be made up of branched, flat fronds secured to a firm surface by a holdfast at the end of a short stalk-like structure.
2
Moulds / YeastsFormed of thread-like hyphae, which spread over the surface on which the mould is growing / Do not grow hyphae but live as single cells
Some of the hyphae carry capsules which contain spores / Spore capsules absent
Extension questions
1 The shape of a molecule of monosodium glutamate (MSG) is different from the shape of a molecule of glutamic acid. The body’s immune system recognises MSG as a molecule not normally found in the body and responds to it resulting in an allergic reaction.
2 Points could include: alkali; treatment; drying; high temperature; washing; purifying;
3 Points could include: restriction enzyme; plasmid; identifying gene; fermenter.
Worksheet B3.1 3a
1 Amino acids.
2 Enzymes, hormones, muscles consist of proteins.
3 Protease enzymes which catalyse the breakdown of proteins.
4 Protein.
5 Less cloudy/clear.
Next Lesson
4 Amino acids are produced. These are absorbed by the microbes and used to make proteins.
5 Washing liquid/powder – where proteins are digested as part of the process of making product.
6 From bacteria cultured in fermenters.
7 Temperature/pH/co-factors.
Worksheet B3.1 3c
1 a Lactose;
b lactic acid.
2 The curds separate from the whey.
3 Lactic acid is present.
4 a An enzyme;
b promotes coagulation of milk.
5 a Because it is not made using GM microorganisms even though the enzyme used in its production is made by GM organisms;
b many people object to eating GM food.
B3.1 4 Eating well
Students’ Book pages
1 When it consists of a mixture of foods selected from each of the four food groups in the correct proportions for good health.
2 Milk and milk products, meat and alternatives (e.g. fish, pulses), fruits and vegetables, bread and cereals.
3 Body mass (kg)/(body height)2(m)2.
4 Points should include: BMI 20 = underweight compared with height; BMI 20–25 = body mass/height ratio ideal for maintaining good health; BMI 25–30 = overweight compared with height but unlikely to cause health problems; BMI 30 = obese compared with height with increased risk of the development of obesity-related diseases.
5 The writing should include how to develop a programme of eating a balanced diet which contains nutrients in the right proportions for good health. Advice might include that the input of energy should not exceed the person’s energy requirements and that fibre promotes the movement of food through the gut. Evidence that obesity increases the risk of developing weight-related diseases should be presented.
Summary exercise
diet, 4, balanced diet, fibre, vitamin C, calcium (or vitamin D), vitamin D (or calcium), BMI
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35/ B3.1 / Answers ® continued
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35
Higher questions
1
Nutrient / Deficiency diseasevitamin A / infections; poor vision in dim light
vitamin D / rickets (soft bones) in children; brittle bones in adults
vitamin E / poorly understood in humans but causes sterility in rats
vitamin K / spontaneous bleeding; long healing time
vitamin B1 / beri-beri; nervous disorders
calcium / rickets (soft bones)
sodium / cramp
iron / anaemia
iodine / sluggish body chemistry
zinc / poor healing (skin complaints)
2 Reasons and explanations might include:
Reason / Explanationwatching a lot of television / lack of exercise
overeating / food is easily available
Extension questions
1 BMI = 35.9. Obese (BMI above 30).
2 Their high BMI is not due to excess fat, but because proportionately they are more muscular/producing more protein. Protein is denser than fat, giving a high BMI.
Worksheet B3.1 4a
1 Answers to nearest whole number: A 27; B 18; C 35; D 25; E 34; F 32.
2 B is too thin; C, E and F are too fat.
3 Some people have a ‘weight problem’. Others are unhappy with their looks.
4 Students should be clear that the rapid loss of weight at the start of a slimming course is usually due to loss of water and not body mass. Use the Internet to search for relevant information.
5 Students should produce a balanced answer which shows how the media and celebrity culture affect people’s perceptions of themselves.
6 Students should use the Internet to search for relevant information.
7 Problems might include: greater risk of developing heart disease, arthritis, diabetes, etc. Use the Internet to search for relevant information.
Worksheet B3.1 4b
1 Putrid gums.
B3.1 5 Feeding the world
Students’ Book pages
1 By crossing two existing varieties, each with desirable characteristics. Crossing concentrates the desirable characteristics of each existing variety into the new hybrid variety. Or the genes controlling desirable characteristics can be inserted into existing varieties (genetic engineering).
2 The offspring of a cross between two closely related species or varieties.
3 Desirable characteristics might include resistance to disease, high yield, resistance to pests, shape/colour of fruit, etc.
4 The insertion of genes from one species into the genetic material of a different species.
5 Advantages include:
· Organisms used to make SCP are fast growing.
· SCP has a high protein, vitamin and mineral content.
6 SCP can be grown in large quantities in fermenters; the fermenters take up little space; the conditions inside the fermenters are controlled and independent of the weather. Disadvantage: people might be reluctant to eat SCP.
7 Student’s explanation might include:
· High yield crops can be quickly produced, e.g. rice.
· More people eat rice than any other crop.
· GM crops resistant to herbicides and insect attack reduce the need for herbicides and insecticides.
· The impact of farming on the environment is reduced.
· Growing SCP reduces the amount of land needed for growing crops and raising livestock.
Summary exercise
breeding, hybrid, fermenters, microorganisms, protein, vitamin (or mineral), mineral (or vitamin)
Higher questions
1 Offspring are clones of their parent. The favourable characteristics of the parent are therefore preserved generation upon generation.
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35B3.1 / Answers ® continued
© Edexcel Limited 2007 Extension Units Science Teacher’s Guide / 35
2 a Reasons might include low rainfall, civil unrest and so on.
b In the first case, development of drought tolerant crops through biotechnology would help to overcome the problem. A biotechnological solution to the problem in the second case is unlikely. Students should aim to make their decisions case-by-case.
Extension questions
1 Students will need to visit their local supermarket and be able to recognise the brand names of foods made from SCP.
2 Students should be guided to itemise the different components of a strategy which meets the needs of a balanced diet.
Worksheet B3.1 5a
1 To prevent contamination of the nutrient solution inside the fermenter.