Diet and Food Production - Unit 2 OCR

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  • Created on: 01-06-13 15:23
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  • Diet and Food Production
    • A Balanced Diet
      • What Is It? - to stay healthy it is important to have a balanced diet as it gives you the right amount of nutrients you need plus fibre and water, there are 5 important nutrients
        • Proteins - needed for growth, repair of tissues, make enzymes
        • Fats (Lipids) - act as energy source, provide insulation, make up cell membranes, physically protect organs
        • Vitamins - different ones have different functions, Vitamin D for calcium absorption, Vitamin K for blood clotting
        • Carbohydrates - provide energy
        • Mineral Salts - different minerals have different functions, Iron for haemoglobin, Calcium for bone formation
        • Fibre aids the movement of food through the gut
        • Water is used in chemical reactions, need constant supply as lost in urination breathing and sweating
      • Malnutrition - caused by too little or too much of some nutrients in your diet, three causes
        • 2. Malabsorpton where your body isn't able to absorb nutrients from digested food into bloodstream causing deficiency illness - coeliac disease reduces absorption of nutrients in small intestine
        • 1. Not enough food so you get too little of every nutrient - third world countries people have little food to eat
        • 3. Unbalanced diet may contain too little of a nutrient leading to deficiency illness, may be unbalanced with too much nutrient - too little iron leads to anaemia, too much fat or carbs leads to obesity
      • Obesity - over nutrition can lead to this, a condition defined as being 20% or more ver the recommended body weight, serious condition that can increase the rate of developing type 2 diabetes or arthritis or high blood pressure or coronary heart disease or even some forms of cancer
        • Main causes are eating too much sugary or fatty foods while getting too little exercise, body takes in more energy than it uses up and excess energy is stored as fat increasing body weight, can be due to underactive thyroid glans
        • Body Mass Index - BMI is used as a guide to help decide whether someone is underweight, normal, overweight or obese, calculated from height and weight : body mass (kg) / height (m)2
          • Below 18.5 is underweight, 18.5 - 24.9 is normal, 25 - 29.9 is overweight, 30-40 is moderately obese and above 40 is severely obese
            • BMI not always reliable as it doesn't take into account how much of a persons body mass is mad up of fat - e.g. athletes have a lot of muscle which weighs more than fat so could have a high BMI although they're not overweight
      • Coronary Heart Disease - result of reduced blood flow to the heart leading to chest pain (angina) and heart attacks, caused by atherosclerosis : narrowing and hardening of coronary arteries, diets high in cholesterol and salt can increase the risk
        • Blood Cholesterol Level - cholesterol is a lipid but also in our diet, some needed for body to function normally as it needs to be attached to protein to move around the body and form lipoproteins : substances composed of protein and lipid, the body able to regulate total level using lipoproteins
          • Low Density Lipoproteins (LDLs) - mainly lipid, transport cholesterol from liver to blood where it circulates until needed by cells, function to increase blood cholesterol when level too low, however high saturated fat diet raises LDL so more cholesterol transported increasing total level, increases build up of fatty deposits in artery wall (atheromas) at places where damage causing atherosclerosis and can lead to CHD
          • High  Density Lipoproteins (HDLs) - mainly protein, transport cholesterol from body tissues to liver where recycles or excreted, function to reduce blood cholesterol when level too high, diet in polyunsaturated fat raises HDL level so more cholesterol transported decreasing total blood cholesterol and decreasing CHD risk,
          • Salt - a high salt diet causes high blood pressure which can increase risk of damage to artery walls, these have increased risk of atheroma formation which causes atherosclerosis and increases CHD risk
    • Increasing Food Production
      • Human Food Supply - humans rely on plants for food as they are the start of all food chains, they use energy from sunlight to convert CO2 and H20 into complex organic compounds, humans and animals then eat digest and absorb compounds needed for energy and growth
        • We grow plants for direct consumption and to feed animals which we then eat, many modern farming methods aim to maximise productivity by increasing plant and animal growth by using different methods
      • Fertilisers - chemicals that increase crop yields by providing minerals plants need to grow, soil minerals are used up in growth so fertilisers replace them so a lack of minerals doesn't limit growth of next crop, two types :
        • Natural Fertilisers - organic matter including manure and sewage sludge
        • Artificial Fertilisers - inorganis matter containing pure chemicals as powder or pellets
      • Pesticides - chemicals that increase crop yield by killing pests that feed on crops, fewer plants are damaged or destroyed, may be specific and kill only one pest species or broad and kill a range, the advantage of broad spectrum pesticides is that they kill a wide range in one go however this means they may harm some non-pest species
      • Antibiotics - animals farmed for food sometimes given these to increase food production
        • Advantages - animals can use more energy to grow and increase food production rather than fight disease, help promote animal growth as they influence bacteria in gut allowing more efficient food digestion, makes it less likely bacterial diseases will pass to humans
        • Disadvantages - can increase change of bacteria becoming resistant so more difficult to treat future disease, animals natural useful bacteria may be killed, antibiotics may be present in animal products humans consume causing unwanted effects
      • Selective Breeding - involves selecting most useful plants of animals to reproduce together increasing productivity, general method : 1. select plant or animal with useful characteristic that will increase food production, 2. breed them together, 3. select best characteristic offspring and breed them together, 4. continue over generation until high yield is produced
        • Crops - often involves selecting plants with characteristics such as high yield or resistance : e.g. corn which is taller with more ears, apples resistant to apple scab
        • Animals - select animals with useful characteristics such as fast growth rate or high meat milk of egg yield : e.g. cows with high milk yield so breeds largest ones
        • Arguments For - produce high yielding animals of plants, produce ones with increased resistance to disease, bred to increase tolerance of bad conditions
        • Arguments Against - cause health problems (chickens grow quickly can cause heart and lungs to be unable to support increasing body mass), reduces genetic diversity as results in inbreeding reducing gene pool
    • Microorganisms and Food
      • Microorganisms in Food Production - used in production of many foods and drinks, some can convert sugar into other substances that humans can use for food production
        • E.g. Breas is mixture of yeast with sugar flour and water so yeast turns sugar into ethanol and CO2, Wine is yeast and grape juice where yeast turns juice into ethanol and CO2
        • Advantages - populations of microorganisms grow rapidly under right conditions so food produced quick, can grow on range of inexpensive material, environment can be artificially controlled, optimum conditions are easy to create, some food made often lasts longer in storage than raw products
        • Disadvantages - high risk of food contamination as conditions created are also favourable to harmful microorganisms which may cause food to spoil or cause poisoning, conditions required can be simple to create but small changes can kill microorganisms
      • Food Spoilage - deterioration of characteristics,can be caused by growth of unwanted microorganisms which multiply and secrete enzymes that break down the food molecules, some may produce waste products that contribute and cause poisoning if food is eaten, very young and elderly people are more likely to be affected by poisoning as they have weaker immune system
      • Preventing Spoilage - either killing or depriving microorganism of conditions needed to grow which stops or slows down growth
        • Salting - inhibits growth by interfering with ability to absorb water, salting lowers water potential of environment outside microbe cell causing water loss
        • Adding Sugar - sugar inhibits growth by interfering with ability to absorb water (see salting)
        • Freezing - keeps food below  -18 so slows down enzyme controlled reaction and freezes water in food so microorganisms can't use it
        • Pickling in Vinegar - vinegar has low pH which denatures enzymes preventing them from functioning and inhibiting growth
        • Heat Treatment - involves heating food in high enough temperature to denature enzyme and kill microorganism present, pasteurisation is one form of this as it involves raising liquids to high temperature
        • Irradiation - involves exposing food to radiation which kills and microorganisms present by destroying or damaging its DNA and can extend shelf life considerably

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