F1 & 2 SCIENCE- BIOLOGY STRUCTURE AND FUNCTIONS OF LIVING ORGANISMS TOPIC: STRUCTURE AND FUNCTION OF LIVING ORGANISMS SUB-TOPIC: • Nutrition in Humans AIM(S): • To examine the content of a healthy diet. • To examine malnutrition. SUCCESS CRITERIA: I can……………… • identify some sources of food components. • explain why each of the components is needed. • calculate the nutrients in a particular diet. • define malnutrition. • state some effects of malnutrition. KEYWORDS: balanced diet, malnutrition, deficiency diseases. NUTRITION • Taking in food for the body to function properly. • Staying healthy is important for all animals. • The food we eat provides the raw materials needed for growth and repair and the energy our bodies need to keep it running smoothly. A diet is the total of all nutrients a person takes in or what a person eats. BALANCED DIET • A diet that contains the right types of food in the right amounts/proportions so that the body can get the nutrients it needs. A healthy diet is made up of 7 components (nutrients). These are; • Carbohydrates • Proteins • Fats • Minerals • Vitamins • Dietary fibre • Water CARBOHYDRATES • They are the bodies main source of energy. The two kinds of carbohydrates are : Simple carbohydrates (sugars) These provide a lot of energy for immediate use. Complex carbohydrates (starches) These are good sources of energy. The body stores this energy easily for rapid use by the muscles. • It should make up about 70% of our solid diet. FATS • Also supply energy when stores of carbohydrate run low. • Contain twice as much energy as carbohydrates. The two types of fats are; • Saturated fats - are solids at room temperature and can be converted into cholesterol. • Unsaturated fats – are liquids at room temperature Excess fat is stored as body fat, causing weight gain. • Fats can be stored beneath our skin where it acts as insulation and helps keeps us warm. PROTEINS • They are used for the growth and repair of cells. • The protein you eat is broken down into amino acids and is used by the body to build cells, make blood and repair and replace tissues. • Weight lifters, athletes, pregnant women and those recovering from an injury require a lot of protein in their diet. • Proteins come either from plant or animal sources. VITAMINS AND MINERALS Vitamins Minerals • Vitamins help the body to work normally. • It helps in resisting infections and diseases. • There many examples of vitamins. • Vitamin C is very important. • Minerals combine with other foods to form parts of the body. • The body needs small amounts of certain minerals in order to stay healthy. • Examples of minerals are; calcium, iron, potassium, sodium, phosphorous etc. FIBRE AND WATER Dietary Fibre Water • Fibre is a substance called cellulose. • It cannot be digested, it aids with free bowel movement. • The body is mainly composed of water. • Approximately 60% of an adult’s weight and 80% of a child’s weight is water. • It aids in digestion, absorption of nutrients and removal of waste. CONSEQUENCES OF IMBALANCES IN THE DIET If the diet does not provide all the nutrients in the correct proportions, a person can starve or be malnourished. Malnutrition occurs when the body does not receive enough nutrients for proper function. The body will suffer severe consequences if there is too much or too little of a particular nutrient in the diet. Dangers of too much of a particular nutrient in the diet are; • High blood pressure • Coronary heart disease • Tooth decay • Obesity DEFICIENCY DISEASES • It is a disease caused by the lack of a particular nutrient in the diet. Below is a list of nutrients and their deficiency diseases. Kwashiorkor lack of protein Marasmus lack of carbohydrate ENERGY REQUIREMENTS IN A DIET We get energy from the food we eat and this is used to carry out all life processes. Our energy requirements depend on our… • Age • Gender • Activity For these reasons, the amount of energy we take in should balance the amount of energy we use. Food can be tested for its energy content using calorimetry so food packets must always show how much energy is present in the food. CALCULATING THE NUTRIENTS IN A DIET The amount of energy that food contains is measured in joules(J) or kilojoules(kJ). Take a look at the table below. RDA for Boys RDA for Girls 100g of wholemeal bread 100g of milk 100g of oranges 100g of butter TRY ANSWERING THESE… • One thick slice of wholemeal bread has a mass of 50g. How much of the following does it contain? Protein Fibre Carbohydrates • A 50g slice of wholemeal bread is spread with 10 g of butter. How much chemical energy is in this snack? • How many grams of oranges would you need to get the recommended amount of Vitamin C ? SUB-TOPIC: DIGESTION AIM: To examine digestion of carbohydrates, proteins and fats SUCCESS CRITERIA: I can……. • explain the role of enzymes in the digestion of carbohydrates, proteins, fats and oils. • explain the use of end products in the body. KEYWORDS: digestion, enzyme, bolus, chyme DIGESTION Nutrition involves a sequence of processes which change food molecules into the sort of molecules that can be used by the body. This process is called digestion and it takes place in a specialised region called the alimentary canal or gut. Stages of Digestion • Ingestion • Physical digestion/mechanical breakdown • Chemical digestion • Absorption • Assimilation • Egestion THE PROCESS OF DIGESTION • Digestion begins in the mouth where food is broken down by the teeth. This is called mechanical breakdown. • The small parts of food are mixed with saliva and swallowed. After food is swallowed it enters the stomach, which is food enters from the gullet basically a muscular bag filled with hydrochloric acid. food leaves the stomach THE PROCESS OF DIGESTION Two things happen to food in the stomach: • the chemical breakdown of food begins; • microbes are destroyed. From the stomach, food enters the small intestine where digestion is completed and the small digested food molecules are absorbed into the bloodstream. THE PROCESS OF DIGESTION • After the small intestine, the remains of any undigested food travel to the large intestine. All that is left of the food is water and waste material. The water is valuable and so is absorbed in the large intestine into the blood stream. Undigested waste travels to the rectum where it is stored until leaving the body through the anus. DIGESTIVE ENZYMES- CHEMICAL DIGESTION • Digestive enzymes are the chemicals that break large insoluble food molecules into smaller soluble molecules. DIFFERENT TYPES OF DIGESTIVE ENZYMES • Digestive enzymes are classified by the type of food that they affect, so there are three main types: • Carbohydrase – breaks carbohydrate into smaller sugars molecules. carbohydrase sugar molecules long carbohydrate molecule • Protease – breaks protein into amino acids. These enzymes work in an acidic environment to break proteins into smaller amino acids. protease long protein molecule amino acid molecules DIFFERENT TYPES OF DIGESTIVE ENZYMES • Lipase – breaks fat into fatty acids and glycerol. Fats are digested in two stages: • First, bile (released by the gall bladder) allows the fat to “mix” with water by breaking the fat into smaller droplets. This is called emulsification. bile • Next, the digestive enzyme lipase breaks each fat molecule into the smaller glycerol fatty acid molecules . lipase fat molecule + glycerol fatty acids DIGESTION SUMMARY SUB-TOPIC:FOOD TESTS AIM: To plan an investigation (simple test) for proteins, carbohydrates, fats and oils. SUCCESS CRITERIA: I can perform simple tests to identify carbohydrates, proteins and fats. TESTING FOR CARBOHYDRATES • Starch is important an important source of energy. It can be found in foods like, potatoes, pasta and rice. Starch digestion begins in the mouth and continues in the small intestines. Enzymes such as amylase(a type of carbohydrase) breaks down starch into glucose molecules which the body can absorb and use for its life processes. • A simple test used to check for the presence of starch in food is the iodine test. VIDEO - TESTING FOR STARCH TESTING FOR CARBOHYDRATES Iodine solution gives a dark blue-black colour when it is mixed with food containing starch. • Reducing Sugars such as glucose can be tested using a chemical called Benedict’s solution. A red-orange colour change indicates the presence of glucose/ sugar. VIDEO - TESTING FOR SUGARS(GLUCOSE) TESTING FOR PROTEINS Proteins aid in growth and repair of cells. Proteins are broken down into amino acids in the body so that they can be absorbed and used. The enzyme responsible for breaking down proteins is called a protease. Fish, meat, eggs, pulses and some nuts are good sources of proteins. Proteins in food can be tested by adding Biuret solution or sodium hydroxide and copper sulfate. A purple or violet colour change shows a positive test. VIDEO - TEST FOR PROTEINS TESTING FOR FAT • Fat is another source of energy for the body. Fat is first emulsified by bile into fat droplets which is then broken down by lipase into fatty acids and glycerol, forms which the body can use or store. You can test for fat by rubbing a piece of food over a plain white paper and hold up the paper towards light. A greasy/translucent mark indicates the presence of fat. VIDEO - TESTING FOR FAT SUMMARY • A diet is the total of all nutrients a person takes in or simply what a person eats. • A healthy diet is made up of 7 components (nutrients). • Deficiency disease is a disease caused by the lack of a particular nutrient in the diet. • The amount of energy that food contains is measured in joules(J) or kilojoules(kJ). • Digestion is a process that breaks down food into smaller molecules for absorption by the body. • Digestive enzymes are the chemicals that break large insoluble food molecules into smaller soluble molecules. • Food substances can be checked in foods by using simple tests.
