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2.2.1 Diet and Food Production

2.2.1 Diet and Food Production. 2.2.1 Specification. Define the term balanced diet Explain how consumption of an unbalanced diet can lead to malnutrition, with reference to obesity Discuss the possible links between diet and coronary heart disease (CHD )

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2.2.1 Diet and Food Production

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  1. 2.2.1 Diet and Food Production

  2. 2.2.1 Specification • Define the term balanced diet • Explain how consumption of an unbalanced diet can lead to malnutrition, with reference • to obesity • Discuss the possible links between diet and coronary heart disease (CHD) • Discuss the possible effects of a high blood cholesterol level on the heart and circulatory • system, with reference to high-density lipoproteins (HDL) and low-density lipoprotein • (LDL) • Explain that humans depend on plants for food as they are the basis of all food chains. • (No details of food chains are required) • Outline how selective breeding is used to produce crop plants with high yields, disease • resistance and pest resistance • Outline how selective breeding is used to produce domestic animals with high • productivity • Describe how the use of fertilisers and pesticides with plants and the use of antibiotics • with animals can increase food production • Describe the advantages and disadvantages of using microorganisms to make food for • human consumption • Outline how salting, adding sugar, pickling, freezing, heat treatment and irradiation can • be used to prevent food spoilage by microorganisms

  3. Balanced Diet Living organisms need vital substances termed nutrients in order to provide energy and materials for growth and repair. Without the regular intake of these nutrients (and oxygen from the air), the organism will suffer ill health and may die The diet of a person is what is eaten and drunk on a regular basis. The components of a diet can be provided by plants, animals, and microorganisms Balanced diet A diet which provides an adequate intake of energy and nutrients needed for the maintenance of the body and thus good health It is the adequate intake of food (mixture of organic and inorganic chemicals) containing the right kinds of nutrients in the right amounts • The Food Standards Agency (FSA) tips for healthy eating • Base meals on starchy foods • Eat lots of fruit and vegetables • Eat more fish • Cut down on saturated (animal) fats • and sugar • Eat less salt • Exercise – maintain a healthy weight • Drink plenty of water • Don’t skip breakfast

  4. There are seven components in a balanced diet Carbohydrates – source of energy – e.g. glucose; starch Fats – energy store; cell membranes; insulation (thermal + electrical); protect organs; storage of fat-soluble vitamins; need to ensure consumption of fats containing essential fatty acids Proteins – growth and repair; enzymes; muscle; antibodies; cell membrane; etc; need to ensure consumption of proteins containing essential amino acids Vitamins (organic) - Fat soluble - A, D, E, K; water soluble - C, B group – for efficient biochemical function; for coenzymes – required in trace amounts.; K – blood clotting, D – calcium absorption; required in trace amounts Water – solvent; reactant; transport – variable; about 70% of the body is water Minerals (inorganic) – structural components and osmotic balance- calcium – for bones, teeth; iron – for haemoglobin;; iodine – for thyroxine (hormone); sodium – for osmotic balance Fibre (organic) – for efficient peristalsis; prevents constipation; lowers blood cholesterol Proportions in diet (for energy intake) - 57% CHO; 30% fats; 13% protein Essential amino acids, essential fatty acids, and vitaminsneed to be provided in the diet – these cannot be made in the body – others can be made Needs vary – e.g. age, occupation, pregnancy, lactation, gender, illness

  5. Essential Amino Acids • Twenty different amino acids are used in the synthesis of proteins • There are 10 amino acids that the body cannot make - these are called essential amino • acids (EAAs), and need to be present in the diet – a balanced diet will contain all the • essential amino acids and a good supply of the non-essential amino acids • Non-essential amino acids can be synthesized from EAAs – e.g.: • The essential amino acid phenylalanine can be converted into the non-essential amino acid tyrosine • “Non-essential” amino acids do not need to be present in the diet • Some roles of EAAs in the body – synthesis of neurotransmitters, hormones, enzymes, • antibodies, structural proteins (e.g. collagen), contractile proteins (actin and myosin) • Proteins cannot be made without the essential amino acids – lack can lead to deficiency • diseases • Effects of deficiency of EAAs: • Poor growth; underweight; poor development • Poor wound healing • Poor immune system (susceptibility to disease) • Muscle wasting • Fatty liver • Some sources of EAAs – meat ; eggs; milk; mixed diet (fruit, vegetables, nuts)

  6. Essential Fatty Acids (EFAs) • The body is able to make all the necessary fatty acids required , except two – linolenic acid and linoleic acid – these have to be present in the diet; they are essential fatty acids; they are unsaturated • They are required in very small amounts – well nourished people have probably a year’s supply in their adipose tissue • Some roles of EFAs – synthesis of prostaglandins (local hormones), steroids, phospholipids (cell membrane structure and function); gene regulation and expression; inhibit platelet adhesion (prevents clotting of blood); development of visual and neural tissue; neurone structure (myelin sheath in neurone) • Effects of deficiencyImpaired vision; mood swings • High blood pressure • Susceptibility to infection • Immune and mental deficiencies • Impaired growth • Scaly dermatitis • Some sources of EFAs – fish and shellfish; plant oils; leafy vegetables; walnuts; milk Linoleic acid (Omega 6) 18:2 – 18 carbons; 2 double bonds Linolenic acid (Omega 3) 18:3 - 18 carbons; 3 double bonds

  7. Malnutrition (“bad nutrition”) • Malnutrition is causedby insufficient, excessive or animbalanced consumption of nutrients – this can be due to: • Lack of food – leading to starvation – resulting in a lack of energy and nutrients • The body adapts by - reducing the metabolic rate, and using stored • micronutrients (carbohydrates, fats, and proteins) • Protein Energy Malnutrition (lack of carbohydrates and protein) - leads to • kwashiorkor& marasmus • Lack of specific nutrients(unbalanced diet) - leading to deficiency diseases • Iron - iron-deficiency anaemia; vitamin C - scurvy; vitamin D and calcium – • rickets; niacin (vitamin B3) - pellagra; iodine – goitre; vitamin A – night blindness • Overeating– more energy consumed than used • Excess energy intake leads to obesity (increase in weight) • Obesity is a risk factor in coronary heart disease; hypertension; diabetes; • cancers (bowel, rectum, uterus, cervix); arthritis; hernias; gallstones – mainly due • to a diet rich in carbohydrates and fats and a high concentration of cholesterol in • blood. Excess carbohydrates is converted to fat and stored around vital organs • (e.g. heart & kidneys) and in females underneath the skin • Other causes • Problems with absorptionand assimilation (utilisation) of nutrients following • digestion causes deficiency diseases – e.g. celiac disease

  8. Deficiency diseases Scurvy – lack of vitamin C Pellagra – lack of niacin (vitamin B3) Goitre – lack of iodine Pellagra – after niacin therapy Marasmus – severe nutritional deficiency Kwashiorkor – lack of protein Rickets – lack of vitamin D and / or Ca

  9. Obesity and Health • Overeating is a form of malnutrition • If the regular intake of energy is in excess of demand, the body gains weight –leading to obesity • Obesity is an increasing problem in “developed” “Western” countries – associated • with the diet (rich in fat) and lifestyle (not physically active) • Fat provides twice as much energy per gram than a gram of carbohydrate or protein, • due to a higher hydrogen content in the fat molecule – therefore, a fat rich diet • increases the risk of gaining weight • Obesity is a growing problem in children – due to consumption of fast foods • (containing fat, sugars ,and starches) and lack of physical activity • Obesity is a risk factor in CHD, diabetes, arthritis, and some forms of cancer • A BMI greater than 30 is classified as obese – obesity is a result of • Eating too much • High fat, sugar, carbohydrate, alcohol in the diet • Energy intake greater than use • Insufficient exercise • Genetic predisposition • Underactive thyroid (low basal metabolic rate)

  10. Body Mass Index (BMI) and Obesity The BMI is used to determine if an adult person is underweight, overweight, or obese It is calculated using the following formula mass BMI = Height2 (m2) • A graph can be used to determine the BMI of a person – however: • If values fall on a line dividing the categories, it is difficult to place in a category • Limitations of BMI • Difficult to calculate BMI for children and • adolescents – since they store fat as part of their • growth • Does not take into account gender, age, disease • (e.g. osteoporosis; thyroid disease) and other • factors contributing to obesity (e.g. lack of • exercise / pregnancy) • Does not take into account muscle mass / bone • mass, or amount of body fat

  11. Example Height = 1.73 m Mass = 75 kg BMI = 75 / 1.732 75 / 2.9929 = 25 BMI = 25 Acceptable A body weight, 20% in excess of the recommended weight for a particular age is considered obese X

  12. BMI vs. Body-fat percentage measurement In September 2000, the American Journal of Clinical Nutrition published a study showing that body-fat percentage may be a better measure of a persons risk of weight-related diseases than BMI. "Many studies have related BMI to disease risk,“ "What we did was correlate body-fat percentage to BMI, allowing us to take the first big step toward linking body-fat percentage to disease risk. BMI is a broad, general measure of risk. Body-fat assessment is much more specific to the actual fat content and thus provides a more accurate picture.” "In terms of ease-of-use and usefulness, the BMI can't be beat,“ "But if a home, fat-measurement device helps someone stay focused on their diet and exercise level and motivated to stay healthy, then the device has a place in weight management."

  13. Obesity – a risk factor in a number of diseases • Coronary heart disease - a diet rich in saturated (animal) fats, leads to a high concentration of blood cholesterol. • A high blood concentration of cholesterol and a high blood pressure (hypertension) increases the risk of developing coronary heart disease – e.g. • Atherosclerosis – build up of fatty material (plaques) in coronary arteries • Coronary thrombosis – blood clotting in coronary arteries • Heart attack • Stroke - loss of brain function due to insufficient supply of blood (oxygen and nutrients) due to a blood clot • Myocardial infarction • Diabetes (type 2)– obese people cannot control their blood glucose , principally due to insensitive insulin receptors • Cancers – colon, rectal, cervical, prostate, uterine, breast • Osteoarthritis (inflammation of the joints) – due to increased strain on the skeleton and joints • Thrombosis – blood clotting in blood vessels of the pulmonary and systemic circulation • Hernias, varicose veins and gallstones • Organ strain – due to organs (e.g. heart, kidneys) being surrounded by excess fat – causes physical strain • Surgery – operations carry an increased risk of complications in obese people

  14. The location of where the fat is deposited has an effect on the acquired conditions • “few moments on the lips, forever on the hips” • Apple shaped – fat around the middle • Higher risk of obesity-related conditions • Pear shaped– fat around hips and thighs • Lower risk of obesity-related diseases • Preventive measures • Incentives (inducements) to lose weight – e.g. • prizes, competitions • Clubs /local meetings / help lines • Target setting for weight reduction / target groups of • people • Change diet (reducing energy foods and fats) • Reduced alcohol intake • Encourage exercise • Advertising / education • Early education to encourage healthy eating • habits and exercise

  15. Diet and Coronary Heart Disease (CHD) A healthy BMI is maintained by balancing the overall energy intake with energy use – to avoid becoming underweight or overweight (obese). Excess intake of certain components in the diet may increase the risk of CHD – a major cause of death in developed countries. CHD is a result of reduced blood flow to the heart – leading to angina, myocardial infarction and heart failure, caused by the narrowing and hardening of coronary arteries – the blood vessels supplying the heart Deposition of fatty material in the walls of the coronary arteries leads to a narrowing of the lumen – thus restricting blood flow to the heart muscle, which may cause oxygen starvation . Energy is not produced and the cardiac fails to contract – lack of oxygen causes the cardiac muscle to die Arteriosclerosis (hardening of the arteries) also occurs – reducing their elasticity and therefore their ability to expand and recoil – the heart has to work harder to force blood through the coronary arteries and may cause the blood pressure to rise and heart muscle to fatigue

  16. Three forms of CHD • Coronary arteries • Narrow arteries that carry oxygenated blood from the aorta to cardiac muscle at high • pressure • Increased risk of damage due to narrow lumen – further narrowed by deposition of plaque • (fatty material) – thus reducing blood flow to cardiac muscle • Reduces supply of oxygen (and glucose) for respiration. Leads to CHD – three forms: • Angina pectoris • Severe chest pain on exertion due to restricted blood flow to cardiac muscle; no death • of heart tissue • Heart attack (myocardial infarction) • Coronary artery becomes obstructed by a blood clot (thrombus) – heart muscle is • starved of oxygen – dies – causes sudden and severe chest pain - may be fatal if not • treated immediately • Heart failure • Due to blockage of a main coronary artery and gradual damage to heart muscle; heart • weakens and fails to pump effectively • Thrombosis • A blood clot (thrombus) may form at the site of the atheroma – may block • coronary artery – leading to myocardial infarction • Stroke • Sudden symptoms - bursting of artery in brain (brain haemorrhage); blockage • of brain artery due to atherosclerosis or thrombus – reduces oxygen for • respiration; causes cerebral infarction; fatal or disabling

  17. CHD is multifactorial – it has many risk factors • High intake of saturated fats- a cholesterol level greater than 250 mg/100 cm3(5.2 • mmol per dm3) of blood – cholesterol is present in fats and is also made from saturated fats • High salt intake; smoking; heredity (familial hypercholesterolemia) • Lack of exercise; overweight; obesity • Diet low in unsaturated fats; diet low in fibre; lack of vitamin D; lack of antioxidants(vitamins • A, C, and E) • Alcohol; stress; age; gender; diabetes; poverty Obesity – causes an increase in blood pressure, causing the heart to work much harder and increasing the pressure on artery walls – promotes deposition of cholesterol Salt – excess salt in the blood decreases the water potential of blood, causing water to enter blood vessels by osmosis and increasing the blood pressure – leading to hypertension – damaging the internal lining of the coronary arteries – an early step in atherosclerosis • Cholesterol is a derived lipid and is insoluble in water. It is essential for • Vitamin D synthesis in the skin • Cell membrane component (regulates fluidity) • Synthesis of steroid hormones (sex hormones; adrenal cortex hormones) • Formation of bile salts • It is mainly found associated with saturated fats in meat, eggs and dairy products. It is also made in the liver from saturated fats • Being insoluble in water (plasma), it is transported in the blood in structures called high density lipoproteins (HDLs)and low density lipoproteins (LDLs)

  18. Lipoproteins and CHD • LDLs (mainly lipid) – “bad” • Composed of - saturated fats + much cholesterol + little protein • A diet high in saturated fats raises LDL levels - increase blood • cholesterol – increase risk of CHD • Transport cholesterol from the liver to tissues via blood • Tend to deposit cholesterol at damaged sites in endothelium of artery • walls. LDL’s are referred to as “bad lipoproteins” • Saturated fats reduce activity of LDL receptors in tissues – therefore, • less cholesterol is removed from blood – deposited in artery walls to • form atheromas • Unsaturated fats increase activity of LDL receptors – decrease LDLs in • blood • HDLs (mainly protein) – “good” • Composed of unsaturated fats + less cholesterol + much protein • A diet high in unsaturated fats raises the HDL levels - reduce blood • cholesterol – reduce risk of CHD – “good lipoproteins” • Transport cholesterol from the tissues to the liver to be excreted in bile • (or recycled); help to protect arteries against atherosclerosis • Reduce blood cholesterol; reduce arterial deposition; and help to remove • fatty deposits - decrease the formation and risk of atheromas Liver cells have HDL receptors

  19. Diet, Lipoproteins and CHD • A diet high in saturated fat and cholesterol increases blood cholesterol levels – increase sconcentrations of LDLs and lowers concentrations of HDLs– more cholesterol is transported in the blood , from the liver to tissues – increases risk of CHD • A low saturated fat diet reduces the overall concentration of lipoproteins • A diet rich in unsaturated fats increases the proportions of HDLs and lowers LDLs in blood – more cholesterol is transported to the liver from tissues – reduces risk of CHD • Eating monounsaturated and polyunsaturated fats helps to reduce the concentration of LDLs in the blood • Cholesterol is derived from many sources – animal fats; eggs; milk; butter • Ratio of HDL to LDL is important • a high blood (plasma) concentration of HDLs reduces thedeposition of cholesterol in artery walls • a high blood (plasma) concentration of LDLs increases the deposition of cholesterol in artery walls • Only a small amount of free cholesterol escapes from LDLs under normal conditions. • A high amount of cholesterol in the LDLs causes increased leakage of cholesterol into the • plasma • Cholesterol is deposited at the site of damage in arterial walls arterial walls – forming fatty • streaks – leading to the development of plaques (atheroma) • An atheroma increases the risk of blood clotting in arteries. • Deposits may start to build up from childhood

  20. Atherosclerosis The main process leading to cardiovascular disease is the accumulation of fatty material (plaque) in artery walls – mainly aorta, coronary arteries, and carotid artery) , narrowing their lumen and thus restricting blood flow to tissues and cardiac muscle Arteries also become hardened and lose their elasticity – termed arteriosclerosis. The fatty material may increase the risk of blood clots , obstructing the flow altogether. Tissue does nor receive enough O2 and nutrients and may die. Plaque – formed due to build up of fatty material (atheroma) under endothelium in artery wall – consists of cholesterol, fibres, dead, muscle cells, platelets, and foam cells (phagocytes with ingested fat). Damage (break) in artery wall encourages atheroma formation – damage may be due to hypertension, or carbon monoxide and nicotine from smoking Deposited material originates in plasma Deposits may start to build up from childhood Plaques in the lining of arteries, make the arteries less elastic and restrict blood flow The condition is called atherosclerosis An atheroma increases the risk of blood clotting – the clot may break off and lodge in coronary arteries – causing myocardial infarction (tissue death)

  21. Artery lining (the endothelium) gets damaged – e.g. by CO; nicotine; high blood pressure • Phagocytes are attracted to damaged site through chemotaxis – to repair damage • LDLs accumulate in the inner coat (smooth muscle) of arteries – under the endothelium at the site of damage (break) as small fatty streaks • White blood cells ingest fats and become foam cells and sink into the lesion • Increase in the growth of smooth muscle and build up of connective tissue around damaged site occurs – causes fibrosis and hardening - causes loss of elasticity (arteriosclerosis) of artery wall – causes an increase in BP • Free radicals released from the phagocytes react with the cholesterol • Fatty material (cholesterol from LDLs), dead muscle cells and platelets are deposited – known as plaque (developing into an atheroma); high blood pressure also increases deposition of LDLs • Artery wall bulges into lumen – causes narrowing and restricts blood flow • Platelets may be activated – release thromboplastin and a. Blood clot may form (leading to ischemia (reduced blood flow); angina and myocardial infarction (death of cardiac muscle) • Normally, anticlotting factors (e.g. heparin in blood) prevent clotting

  22. The endothelium covering a plaque may rupture - to cause the formation of a blood clot (thrombus) Tear in artery wall Macrophage cell Cholesterol deposits Red blood cell (in lumen) Macrophage foam cell Fat deposits

  23. Evidence Linking CHD to Diet Risk factors in CHD have been identified through long-term epidemiological studies Whitehall Study- with large groups of people – based on lifestyle, illnesses, and cause of death Common factors - identified: Hypertension High cholesterol levels in blood Smoking Diabetes Exercise – reduced incidence of CHD MONICA (1979) – WHO – study of global distribution of CHD Identified a correlation with blood pressure and blood cholesterol as key factors in predicting the likelihood of CHD developing in a person Found higher levels of vitamin E (antioxidant ) in people from countries with low rates of heart disease High incidence of CHD in Finland – linked to a diet rich in animal fats Lowest rate of CHD in Spain and Italy – linked to a high intake of unsaturated fats – which tends to lower blood cholesterol levels, so long as saturated fat intake is low But – France has lowest rates of CHD, although the intake of animal fats is high – suggests that saturate fat and cholesterol intake alone are not important Other dietary factors may be important (e.g. salt intake)

  24. Exam Question & Marking Scheme Human populations with diets high in animal fats have a lower life expectancy than those with diets high in vegetable oils • Suggest one difference between lipids from • animals and those from plants • Animal fats are thought to raise blood • cholesterol levels. High blood cholesterol • can lead to premature death • The Figure shows the relationship between blood cholesterol level and annual death rate per 10 000 of the population Describe the trends shown in the Figure Increased blood cholesterol levels are associated with certain medical conditions Suggest two medical conditions that may be associated with increased blood cholesterol levels Animal fats are saturated Fatty acids have no / fewer, double bonds Animal fats are solids at room temperature Death rates for men greater at any concentration

  25. Food Production • The Sun is the ultimate source of energy for all living organisms • Plants are photoautotrophs – i.e. they are able to make organic chemicals by using energy from sunlight and the inorganic substances, carbon dioxide and water, through the biochemical process of photosynthesis. Plants convert light energy to chemical energy in the form of glucose • Carbon dioxide + Water • Glucose + Oxygen • Plants are at the start of all food chains – all animals rely on plants for food • Food chain – a linear sequence showing feeding relationships – arrows indicate direction of feeding – i.e. flow of energy and materials. • Food chains are interlinked in nature to form food webs • Glucose is - • Broken down to release energy • Converted to other molecules amino acids, fatty acids, etc) All food molecules ultimately come from autotrophic plants The sun is the ultimate source of energy for all living organisms

  26. Making food production more efficient • Humans are omnivores - they eat both plants and animals • Ultimately, all living organisms depend on plants for food • Increase in human population numbers has led to an increase in demand for food. • The challenge is to increase food productivity to provide components of the diet for a • rapidly growing population • In order to meet the demand, the production of foods (derived from microorganisms, • plans, and animals) needs to be made more efficient and cost effective • A number of methods are used to increase productivity of foods derived from living • organisms Methods to increase productivity • Plants Improve growth rate of crops to improve yield – by using fertilisers (chemicals) • Reduce losses of crops due to disease and pests – by using chemicals (pesticides and herbicides) • Standardise plant size to make harvesting easier • Improve plant responses to fertilisers • Selective breeding – to produce plants with desired characteristics (phenotype) – e.g. high yields • Genetically modified plants – to confer resistance to pests, drought, etc; to improve texture , shelf life, etc

  27. Animals Improve rate of growth Increase productivity Increase resistance to disease – use of antibiotics to prevent or treat bacterial disease – promotes growth Selective breeding – to produce animals with desired characteristics - e.g. increased milk and meat yield Microorganisms Use of microorganisms as edible food (e.g. single cell protein) Using metabolic products (e.g. lactic acid to produce yoghurt; antibiotics to promote growth in animals) Selective Breeding (Artificial Selection) Nature selects and allows the survival of species (varieties) that are well adapted to the environment. They are selected as a result of natural environmental forces or pressures Natural Selection is the principle by which each slight variation (adaptation) , if useful, is preserved and passed onto the next generation Humans apply selection pressures to populations in order to achieve the exaggeration of certain features – one method commonly used in food production is selective breeding

  28. Selective breeding involves the following three stages Stage 1 Isolation Select a pair of plants or animals with the desired characteristic (e.g. disease resistance) Allow the pair to reproduce Stage 2 Artificial selection Select offspring with the best combination of the desired characteristics Stage 3 InbreedingAllow selected offspring to reproduce Selection and reproduction is continued for many generations, resulting in the required characteristics becoming more exaggerated in the population. Detailed records are kept to monitor and prove ancestry of valuable individuals The alleles for the undesired characteristics (which otherwise may be useful) decrease in frequency, and in many cases may be lost - e.g. disease resistance A gardener wants to eliminate thorns from a plant The majority of plants have more thorns and dominate those with fewer thorns The gardener selects the plants with fewer thorns (orange coloured plants) and allows them to reproduce

  29. Examples of selective breeding Cattle Increase milk and meat yield; increase milk and meat quality Salmon Increase rate of growth – reduce time to market; improve disease resistance and meat quality Chickens Increase egg production & meat yield Tomatoes Flavour; disease resistance – allele for disease resistance from wild tomato – bred into domestic variety Apples Disease resistance; flavour, texture, and colour Wheat Improve yield;, disease resistance; drought resistance; uniform size (for harvesting) Rice To improve nutritive value – e.g. vitamin A content (“Golden Rice”) Flowers Producing new combinations of colours and scents in garden flowers Thanks to selective breeding (not genetic engineering), cauliflower in different colours are available. They taste the same as white cauliflower, but are just, well, more fun on the plate. Scientists are also claiming that they might be healthier for you than white cauliflower because of the benefits from the compounds that give the vegetables the colour. Healthier than white or not, if its being colourful makes you and your family eat it, that's all the better!

  30. Selective Breeding – Plants Increasing yield (e.g. high yielding wheat plant a plant which can grow tall and produce multiple ears) Select a pair of plants with desired characteristics with (dominant alleles) Breed : Tall corn plant X Corn plant producing multiple ears Select the offspring with the best characteristics Tallest with most ears – breed them together Continue over several generations Until a high yielding plant is produced – very tall with multiple ears Need to preserve genetic diversity off species and keep gene pool as diverse as possible Hybrid – cross between genetically dissimilar parents • Marker-assisted selection • A section of DNA is used as a marker (probe) to recognise the gene for the desired • characteristic in offspring produced from selected parents – allows selection of offspring • for breeding at an early stage • Desired allele can bred into a domestic variety

  31. Plants with a high yield and resistance to disease or pests • Plants showing a high level of resistance to disease or pests are bred together • Offspring showing most resistance are then bred together • Continued over several generations to produce a crop that is disease or pest resistance • Breed Resistant wheat X High yielding wheat • Prevent self pollination (by removing anthers or placing a bag over stigma) • Select best offspring – good yield and disease resistance • Back cross to high yielding wheat(offspring crossed with high yielding • plant) • Interbreedbest offspring with both characteristics • Breed and select for many generations • Mildew (a plant parasite) may adapt to overcome resistance in wheat • Genetic variation occurs due to mutation • Fungus produces a large number of spores • Wheat resistance acts as a selection pressure • Individuals that overcome resistance have selective advantage – likely to survive • Pass on mutated allele (to overcome resistance) to off spring • Increase in allele frequency occurs in successive populations

  32. Selective Breeding – Animals • Useful characteristics selected for – e.g. fast growth rate; high meat, milk or egg yields • Meat yield • Breed: Largest cows X Largest bulls • Select offspring with the best characteristics • Breed them together • Aberdeen Angus Bull • Continue over several generations – until cows with very - bred for meat yield • high meat yields are produced – i.e. very large cows (or bulls) • Milk yield • This is done in a similar way, except – • Bulls are chosen whose female relatives • have high milk yields and who produce • female calves with high milk yields • Health and welfare of the animals should not be compromised – e.g. high milk yielding cows have a higher tendency to suffer fro mastitis (inflammation of the udder) and lameness

  33. Frozen semen from selected bulls can be • Frozen and kept for long periods of time and quickly available when needed • Transported over long distances • One bull can be used for breeding with a large number of cows – prevents inbreeding • Costs of transport of animals for mating, and the stresses of mating are avoided • Sperm can be sexed and checked for genetic defects • Disadvantages • Low temperature storage may damage sperm • If the sperm used to inseminate a large number of cows have a genetic defect – the cost may be high • Failure of freezing equipment or loss of power supply • Disadvantages of selective breeding • Growth may be too rapid • Possibility of increased susceptibility to disease • Inbreeding • Reduces genetic variation

  34. Selective breeding of domesticated animals is an example of artificial selection, which occurs when man directly intervenes in the breeding of animals to produce desired traits in offspring • As a result of many generations of selective breeding, domesticated breeds can show significant variation compared to the wild counterparts, demonstrating evolutionary changes in a much shorter time frame than might have occurred naturally • Examples of selective breeding of animals include: • Breeding horses for speed (race horses) versus strength and endurance (draft • horses) • Breeding dogs for herding (sheepdogs), hunting (beagles) or racing (greyhounds) • Breeding cattle for increased meat production or milk • Breeding zebras in an attempt to retrieve the colouration gene from the extinct • Quagga

  35. Inbreeding (“in family” breeding) • Continuous inbreeding and selective breeding of particular genes (characteristics) to achieve the desired characteristics leads to • Reduced gene pool (genetic diversity) in long term • Risk of losing genes – offspring may end up with similar genome • All offspring susceptible to new disease – may be fatal • Offspring unable to cope with other environmental stresses – e.g. killed by pesticide Selective breeding compared with evolution • The selection pressure in evolution is natural selection, involving the whole • environment of the organism. • In selective breeding, the selection pressure is the artificial selection that results • from the breeder’s choice of parents. • In selective breeding, the change selected may not be an advantage to the • organism in its environment. • In evolution, the organism’s adaptation to the environment is favoured • One character may be selected, whereas in evolution the organism’s total fitness • for its environment is selected The change is commonly faster than that achieved by natural selection

  36. Using Chemicals to Improve Food Production • Fertilisers • Minerals in soil are used up during crop growth. • Fertilisers are chemicals added to soil to provide (replace) essential minerals (mainly N, P, and • K) required by the plant for growth - fertilisers increase the rate of plant growth and therefore • increase the yield • Provide minerals required for biochemical reactions and structural components in the plant • NDNA/RNA nitrogenous bases; amino acids; vitamins • P ADP/ATP; nucleic acids; phospholipids (cell membranes) • K Stomatal opening, osmotic balance • Fertilisers can be natural (compost; manure) or artificial (man made) • Organic fertilisers improve soil structure – retain water, help root growth, provide a slow release of nutrients on decay • Adding fertiliser increases yield to a point – any extra fertiliser is wasted. Fertiliser needs to be added while the plant is growing actively • Adding large amounts of fertiliser may decrease the yield - the high concentration of mineral ions decreases the water potential of the water surrounding the root hairs, causing water to be lost from the roots down a water potential gradient by osmosis • Leaching of excess fertiliser may pollute streams , rivers, and lakes – resulting in eutrophication and death of aquatic life • Fertilisers are removed from the soil during harvesting

  37. Ammonium nitrate is a widely used fertiliser and is manufactured in industry • The nitrogen is used by the plant for • making amino acids (proteins) and • other nitrogen containing chemicals • Using manufactured fertilisers allows • the farmer to apply the right quantity of • fertiliser • Using manure gives an idea of how much • should be used to get the best yield • Pesticides • Pesticides increase crop yields by killing pests (insects, rats, snails) that • feed on the crops – they increase yield by preventing damage and • destruction of crops. Include insecticides, rodenticides, and fungicides; • herbicides are used to kill weeds • Broad spectrum – kill a range of different species – non pest species may also be harmed • Specific – kill only one species • Animals may be treated topically with pesticides – e.g. to kill ticks that live in wool (e.g. sheep) by dipping • Danger of pollution – bioaccumulation in food chain; persistence in environment Liquid copper is uses as a fungicide – to treat raspberry cane blight

  38. Herbicides (“weed killers”) Chemicals that are used to kill unwanted plants (“weeds”) Mechanism of action- photosystem inhibition (in chloroplasts) – inhibits photosynthesis - specific enzyme inhibition – e.g. to inhibit amino acid synthesis • Problems with pesticides and herbicides • Pesticides (and herbicides) for agriculture are specially formulated to decompose rapidly • after application to avoid pollution and undesirable effects on other organisms (e.g. through • bioaccumulation in food chains) – however these do not provide long-term control • DDT is not biodegradable – builds up in the body of the insect • Animals near the top of the food chain accumulate large amounts of DDT in their tissues and may cause the death of the animal (e.g. birds of prey) • Some non-pest species are also harmed and may disrupt the balance of the ecosystem – • e.g. killing of pollinators such as bees • May need to be applied several times during a growing season – this is expensive • Development of pesticide resistance - due to mutation (natural / random)- resistant survive • Resistant will pass on resistant allele (mutation) for resistance to offspring • Higher proportion of resistant individuals in population • Pesticide may persist in the food being consumed , causing health problems

  39. Development of resistance in the pest population • Variation exists in insect population • Insecticide exerts a selection pressure • Some are resistant • Mutation (natural / random) • Resistant survive (non-resistant die) • Resistant will pass on, allele (mutation) for resistance to offspring • Higher proportion of resistant individuals in population • Biological pest control • Natural predators (e.g. Ladybirds) of pests can be employed to control pests (e.g. aphids) • Ladybirds feed on aphids • Avoids the hazards of pesticides • Nemaslug contains concentrated doses of nematodes, which are specific natural enemies of slugs • Long term solutions • The use of pesticides to kill pests (e.g. Insects) is a short term solution • A long term solution would be to use of selective breeding to create a crop strain • resistant to the pest

  40. Antibiotics Antibiotics are chemicals that kill or inhibit the growth of bacteria – they are used in the treatment of bacterial diseases – e.g. respiratory infections They are selectively toxic to the bacteria – they do not harm host cells Antibiotics are mixed in the feed of animals or administered in order to increase yield – they help to increase the growth rate of animals and their size when mature • Antibiotics help to treat or prevent disease caused by bacteria - enable animals to be • free of disease • The body uses energy to fight infection – in phagocytosis, inflammation, fever, and the • immune response – this reduces the amount of energy available for growth • Disease free animals do not need to expend energy in dealing with pathogens • Antibiotics therefore, enable the animals to use the energy for growth and not in fighting • infection – thus increasing he yield of milk and meat • Antibiotics reduce the spread of disease among animals that are intensively farmed and in • close proximity to each other – this also helps to improve the yield, since transmission of • infection is to other animals is prevented • Antibiotics also promote growth by influencing gut bacteria – allowing efficient digestion • and preventing unnecessary fermentation – the energy being energy diverted for growth • Increases growth rate and size when mature

  41. Problems with the use of antibiotics • encourages the development of antibiotic resistance • antibiotic resistant pathogens passed along food chain to other organisms • antibiotics passed onto other organisms through food webs • Development of antibiotic resistance • Initially, a population of bacteria will contain • members who have a range of resistance • to antibiotics. Each circle represents a • bacterial cell and the darker the colour, the • more resistant the bacterium is • If the population is then exposed to • antibiotics, the bacteria that are not • resistant will be killed. However, highly • resistant bacteria will survive • Some bacteria will mutate as a result of the • selection pressure created by the antibiotic • and become resistant • If these bacteria are not killed by the • immune system, they will reproduce – and • the daughter cells will inherit the resistance • Thus, over time, the population becomes • more resistant to the antibiotic

  42. Microorganisms and Food Production Microorganisms such as bacteria, yeast and other fungi, have been used traditionally in all parts of the world for producing food for human consumption. This has recently been exploited on a commercial scale Yoghurt Made by adding Lactobacillus bacteria to pasteurised (heat treated) and cooled milk Bacteria use the lactose sugar in milk to produce lactic acid, which causes the milk protein to thicken (curdle) due to the acidic pH and impart a sour taste Temperature is controlled to maintain flavour and texture of the product Cheese Milk is curdled using a protease enzyme (rennin). The curds are then acted on by Lactobacillus. Additional flavour can be given – e.g. by allowing the controlled growth fungi (such as Penicillium) in the cheese

  43. Bread Leavening of bread due to CO2 produced by yeast (fungus) by respiration – the CO2 becomes trapped in pockets of protein (gluten) in the dough, created by kneading, which makes the dough rise due to expansion of the gluten pockets on baking in a hot oven Glucose CO2 + Ethanol Wine Yeast + grape juice (glucose) Ethanol (wine) + CO2 Single cell protein (SCP) SCP is used as edible food – e.g. mycoprotein is made from the hyphae (filaments) of the fungus Fusarium A continuous culture is used to grow Fusarium to make SCP The fungus produces protein with a similar amino acid profile to animal and plant protein It is heat treated (to kill bacteria) and marketed as a meat substitute for vegetarians (QuornTM ) and as a healthy option for non-vegetarians, as it contains no animal fat or cholesterol Fungi can use a wide variety of waste material as nutrients (whey, paper) for growth – economically advantageous No mechanical stirrer is used – to prevent breakage of the fungal hyphae Hyphae of Fusarium graminearum Ammonia provides nitrogen for amino acids (protein)

  44. Exam Question & Marking Scheme Microorganisms, such as the fungus Fusarium, can be grown and then purified to produce mycoportein. The mycoprotein can be used as a food as a food source for humans The table compares mycoprotein with beef Use the data to describe and explain the advantages and disadvantages of using microorganisms to produce food for human consumption Lower / less, energy than beef; useful for slimming / weight control Lower / less, total fat; low / less, saturated fat; lower cholesterol Lower risk of CHD / heart attack / atherosclerosis / stroke / hypertension Lower / less, iron content; increased risk of anaemia / fewer RBCs / less haemoglobin / reduced oxygen carrying capacity of blood Lower / less, protein (only 12 g per 100g); affects growth and repair of tissues Mycoprotein provides more balanced diet Need larger intake to meet requirements

  45. With climate change threatening the availability of land for rearing livestock and the growing awareness of the environmental impact of meat production, mycoprotein may yet be set to fulfil its original mission; to provide the world with a nutritious, abundant, environmentally friendly protein • Advantages of using microorganisms for food production • Grow rapidly under right conditions (pH, temperature, nutrients, oxygen) – protein • Production is much faster than animals – resulting in faster production of food • (compared to growing crop plants and rearing animals) • Their optimal growth conditions can be easily created artificially to maximise yield and • controlled – allowing year round food production – not affected by seasons or location • Production can be regulated (increased or decreased) according to demand – by • controlling their environment • Grow on a range of inexpensive materials – utilises recycling of waste products – • economically favourable • Food produced by microorganisms has a longer shelf life than raw products they're • made from – e.g. cheese lasts longer than milk • Provide a good source of protein (having a complete amino acid profile) for • vegetarians • Protein contains no animal fat or cholesterol • No ethical animal welfare issues

  46. Disadvantages of using microorganisms • High risk of food contamination – conditions are also favourable to harmful organisms • – may cause the desired product to spoil or if eaten cause illness (food poisoning) – • may be fatal • Small fluctuations in the optimum conditions (e.g. temperature; pH) may kill the • microorganisms • Pathogenic microorganisms may grow alongside the useful microorganism and • produce toxins • Aseptic techniques need to be employed in culturing microorganisms • Protein has to be purified – to ensure it is not contaminated • Taste and palatability may be affected – not the same as protein from traditional • sources (mainly animals) • Down stream processing – separating protein from waste may be time consuming • and expensive – risk of contamination • Objections to eating food grown on waste and produced by microorganism • Specialist laboratory facilities may be needed for production o an industrial scale – • demanding investment which may not be possible in some developed countries • Long term effects not known

  47. Food Spoilage by Microorganisms and Preservation of Food • Microorganisms obtain their nutrients by feeding on organic • material around them and at the same time produce and excrete • waste products that spoil food and make it unsuitable for consumption • The main ways in which microorganisms spoil food, or make it unattractive and unsuitable to eat are: • Visible growth Fungi (mould) growing on food – e.g. the bread moulds (Mucor and Penicillium) • Extracellular Bacteria and fungi secrete digestive enzymes digestion extracellularly and then absorb the soluble • nutrients • Eventually, all the food will be turned into liquid • and the food no longer suitable for consumption • Toxins Some bacteria and fungi produce toxins – e.g. • Clostridium spp produces the powerful deadly • bacterial toxin botulin • The cholera bacterium produces a toxin which • causes vomiting and diarrhoea • Pathogenic microorganisms in food may cause disease directly – e.g. • the Salmonella bacterium attacks the lining of the stomach and small intestine – causing food poisoning, which may be fatal

  48. Food preservation Prevention of food spoilage involves inhibiting the growth of microorganisms or killing them – by depriving them of the conditions they need to grow. The food must then be packaged to prevent further contamination with microbes Preservation increases the shelf life of the food Food should be eaten within required time - while it is fresh; by the sell by/expiry/eat before, date Salting (dehydrates microorganisms) Adding salt to food – prevents microorganisms from absorbing water (needed to survive) by osmosis by creating a very low water potential around the microbial cell. E.g. salted meats; gherkins and eggs in brine Sugaring (adding sugar) Similar effect to salting. E.g. high sugar content of fruit jams; tinned fruits Pickling – in acidic vinegar Acidic pH - denatures enzymes and other proteins – changes tertiary structure of enzymes (and active site) and other proteins - inhibits microbial growth. e.g., pickled onions Freezing (below -180C) – long term Slows down biochemical reactions (inactivates enzymes) and freezes the water – microorganisms cannot use the water; immobilises enzymes; ice damages cells; no reaction medium available; microbes cannot move Drying Dehydrates microorganisms – water leaves by evaporation

  49. Heat treatment Heat food to high temperature – kills all microorganisms present – store in an air tight sterile container - e.g. sterilised milk in bottles; canned meats; denatures biological molecules Pasteurisation – heat liquids (e.g. milk) to a high temperature (720C) for a short time (15 seconds) and cool rapidly (to 40C) and store in sealed container at low temperature. Kills most microbes but not spores Irradiation Expose food to ionising radiation (e.g. X-rays, gamma rays, UV) – damages DNA. Kills any microorganisms present and prevents replication– extends shelf life considerably; cannot eliminate toxins already produced by microorganisms Cooking Heat denatures the enzymes and other proteins in microbes – kills microbes; denatures enzymes and other proteins; disrupts microbes Smoking Forms a hard dry surface – smoke contains antibacterial substances (e.g. sodium benzoate) – e.g. smoked fish To prevent further contamination Canning –food heated to denature proteins and sealed in airtight cans Vacuum packing – excludes air – microbes cannot respire aerobically Plastic or paper packaging – prevents microorganisms coming into contact with food

  50. Exam Question & Marking Scheme In Scotland, in 2007, there was a major food poisoning outbreak that killed three people Suggest one group in the population that is more likely to die from food poisoning and give a reason for your suggestion The food poisoning outbreak involved the bacterium Escherichia coli 0157 (E coli 0157) which had been responsible for contaminating meat products . The meat had been stored at 110C rather than the recommended 50C and this led to meat spoilage Explain how bacteria cause food spoilage Food normally spoils much faster if stored at temperatures higher than 50C Explain why food spoils faster at higher temperatures Food can be preserved by keeping it at low temperature in a refrigerator or freezer Name two other methods of food preservation and state how each method works

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