how to keep our bodies healthy main types of food substances and their functions the building blocks of carbohydrates, lipids and proteins how to test for different food substances the importance of water to the human body how food is digested and absorbed the role of enzymes in digestion the structure of teeth [3 oral diseases and oral care the importance of a balanced diet infectious diseases and their prevention how non-infectious diseases are related to unhealthy lifestyles cancer and diabetes biotechnology and healthMr. Chan is 40 years old. He is an office He has lunch in a nearby restaurant every day. worker. He takes the MTR to work every He eats mostly meat and rice, but very few day. vegetables. He often drinks sugary soft drinks. He has a busy job and usually leaves the He notices that his body mass has increased. office at 7 pm. Then he goes home to have He goes to see a dietitian for advice. dinner and to watch TV. He does not do any exercise. @ Your task Imagine you are a dietitian. What advice would you give Mr. Chan? You may have some ideas after studying this Unit. Let’s start! @ detton 885 a 4 2 ge 2Q@ Allanswers OD TE Do you think you are healthy? What is the meaning of being healthy? According to the World Health Organization (WHO), a healthy person should have good physical health, mental health and social well-being. In this Unit, we will focus on physical health. What can we do to keep our bodies healthy? What is a healthy body? Look at the picture below and answer the questions that follow. 1. Do you want to be the people in front of the mirror or their images in the mirror? Why? oO 2. Discuss with your classmates what habits we should develop to keep our bodies healthy. a a Ss.QTE 12 Abalanced diet » Abalanced diet helps us ‘grow, support daily activities ‘maintain body functions and ‘control body mass. To keep our bodies healthy, we need to develop a healthy lifestyle. Enough rest > Young people between 14 to 17 years old need 8 to 10 hours of sleep each day. > Sleep helps us grow, repair body cells and resist diseases. Avoid smoking, alcohol and drug abuse » Smoking causes harm to our lungs, heart and blood vessels, leading to lung cancer and cardiovascular diseases. > Abusing alcohol or drugs badly affects the function of our brain land damages our organs. Appropriate physical activities > Physicalactivties help us control body mass, strengthen body functions and resist diseases, Good hygiene > Good hygiene is important ‘for preventing diseases. 12.1. Ahealthy lifestyle is required to keep our bodies healthy. A healthy lifestyle is essential for building a strong and healthy body and preventing diseases. We should also avoid smoking, alcohol and drug abuse because these substances have harmful effects on the body. heathy festye ARES at balanced det 858K carlovesculadsese Physicalocunty 38) deoe 4 Iygiene fiQ@ Allanswers OD TE * To keep our bodies healthy, we need to develop a healthy lifestyle. © A healthy lifestyle includes: having a —__C) diet, appropriate amount of —___C_____ activities. and enough rest; also practising good —__ and avoiding smoking, alcohol and drug abuse. Physical activities for different age groups Search information on the appropriate amount and intensity of physical activities for people of different age groups. Then complete the table below. Recommended amount and intensity RAO art oer Oa re ECan ESCs at least __ C3). minutes of moderate physical activities a week; or __CQ)—— Q 65 and above | minutes of vigorous physical activities a week A Qe Q ® o @ 12.1 Exercises to train body fitness ‘We can do different types of exercises to improve our strength, endurance and body suppleness. Explore more on our web. er Marathon running requires high endurance. vigorous SUP body suppleness S¥RNAERRE strength 28 endurance Fids@ TE © Allanswers WP a ean aouy 12.2 Nutri on and health ® Main types of food substances People in different countries have different diets. There are many choices of dishes. Despite the differences in our diets, we can all obtain the food substances we need. 12.2. Different dishes provide the same food substances. There are six main types of food substance: proteins, vitamins, minerals and dietary fibre. arbohydrates, lipids, Carbohydrates, lipids and proteins are primary food substances. They are essential for supporting life. Vitamins, minerals and dietary fibre are protective food substances. They are important for keeping, the body healthy. Petree ‘substances Eo Fig. 12.3 The six main types of food substances. * Primary food substances include Oo and Oe * Protective food substances include ase TEREST, eteeiee Ee a ile it primary food substance ARNO ge actbetodsubtnce AEROIt we take in too much carbohydrates, our bodies convert the excess into fats, which are _,, stored unde the skin carbohydate BK starch 388 sugar 1 CD Allanswers CB TE 1. Carbohydrates Carbohydrates are the main source of energy for our bodies. Two common examples of carbohydrates in our diet are starch and sugar. Starch is a complex form of carbohydrates, It is found in foods such as rice, bread and potatoes. Sugar is a simple form of carbohydrates It tastes sweet and is soluble in water, Sugar is found in fruits, candies and cakes, Examples of sugars include glucose, sucrose, maltose and fructose chocolates and candies anna 12.8. Foods richin sugar After we take in food containing starch, the starch is broken down into glucose, which is then transported to body cells. Glucose is used by body cells to release energy during respiration. The energy released is used to support body activities. Carbohydrates are the main source of ______ for ‘our bodies, slucose HERR fructose FRE sucrose ER imotose 278 7@ TE A Healthy Body pid aR cary oll Two examples of lipids in our diet are fat and oil. Fat is solid at room temperature. It is usually found in animals. Meat, lard, butter and cheese are rich in fat. Oil is liquid at room temperature. It is usually found in plants. Examples include peanut oil, corn oil and canola oil. = peanuts and peanut butter Foods rich in lipids Lipids are essential to our bodies. The major functions of lipids are: © Energy storage-When our bodies are short of carbohydrates, the body uses the stored lipids to release energy. © Keeping warm-tipids stored under the skin act as an insulator of heat to keep us warm * Protecting organs—Lipids stored around internal organs act as a soft cushion to protect these organs against shock. © Forming cell membranes—tipids are a major component of cell membranes. int The functions of lipids in the body include: energy storage, keeping warm, protecting organs, and forming cell membranes. lad Be enol ol) FEE@ TE 3. Proteins rotein taken into our body is Prote digested to amino acids. Excess ‘amino acids willbe converted into Muscles, bones, skin, hair and blood. They are essential for growth sare a major component of many body tissues, including cacbohyrates an some waste covponysrtes and somsvaste and repair of our body tissues, especially in children and young passed out ofthe body inure. people. {You wil earn more about amino season eiay When our bodies are short of both carbohydrates and lipids, proteins can also be used to release energy. Fish, meat, eggs, dairy products and beans are rich in proteins. No milk cheese nuts and beans fish Fig. 12.7 Foods richinproteins Proteins are essential for growth and repair of our body tissues. Learn more Kwashiorkor Kwashiorkor is 3 disease caused by a lack of proteins in the diet. It is more common among children in developing countries. Kwashiorkor patients have weak muscles and a swollen abdomen. They may also suffer from poor physical and mental development. K © Child suffering from kwashiorkor protein EER amino oid #388 sstorkor este 5510 ® TE AHealthy Body 4. Vital iS Vitamins have no energy value, but are essential for maintaining the normal functions of cells and organs in our bodies. Only small amounts of vitamins are needed. They help promote growth and development, regulate metabolism and strengthen immunity. Each vitamin has important functions. The lack of any vitamin in our diet may lead to deficiency diseases. Some examples are shown below. oo Functions: Deficiency disease: + night blindness—poor vision in dim light * important for vision in dim light fish ver oi > immunity Dairy products, carrots, fish liver oil and dark green vegetables are rich in vitamin A. | * strengthening Functions: Deficiency disease: * maintaining healthy * scurvy—gums bleed and skin and gums & &) wounds heal poorly * healing of wounds — Je Frosh fruits and vegetables aro ich in vitamin C. 7 scury Funct Deficiency disease: * maintaining strong * rickets-bones bones and teeth become soft and bent Mil, fish liver oll and egg yolk are rich in vitamin D, rickets Functions of some vitamins and the related deficiency diseases scurvy Sms metabolism SFR BRUER neko Immunity 28/3 right blindness EE5. Minerals Similar to vitamins, minerals have no energy value. We need small amounts of minerals to maintain a healthy body. Minerals are needed to regulate metabolism. Some of them are used to form body tissues. For example, calcium is used for building bones and teeth. The lack of minerals in our diet may lead to various deficiency diseases. Some examples are shown below. eS Functions: € * building bones {tickets in children and teeth 5 és i Deficiency diseases: * osteoporosis—bones * blood clotting become weak in adults Function: Deficiency disease: + making haemoglobin in red blood cells + anaemia—number of red blood cells is lower than normal, leading to pale skin, tiredness and fainting Red meat, iver nuts, beans and dark {green vegetables are richin ron. Deficiency disease: * maintaining the functions of the thyroid gland * goitre—the thyroid gland becomes swollen ‘Seafood and seaweed are rich in iodine. a ey goitre Fig. 12.9 Functions of some minerals and the related deficiency diseases _ mineral BOE hemoglobin ns osteoporosis {tyrod glond 8 4KEE anaemia $b ‘odine u@ TE © Allanswers AHealthy Body 12.2 lodine deficiency in Mainland China lodine deficiency is a common problem in some areas of China. To solve this problem, the government of China started 4 programme in the 1990s to provide people with iodized salt. Explore more on our Web. Gone - © lodized salt Deficiency diseases The people below suffer from various deficiency diseases. In each case, name the disease that the person suffers from. Also, state the food substance(s) they may lack in their diets. Then suggest THREE types of foods that they should eat more. (a) Deficiency disease: Food substance(s) she lacks: Foods to eat more: (b) Food substance(s) he lac Foods to eat more: (co) Deficiency disease: Food substance(s) she lacks: Sooo oe oe Deficiency disease: soo Cpe SEEEeEe Cope eeL oe SERRE eG eee oD a od x Foods to eat more: Jodied sale 8 12etary be SFR persis $8) re Dietary Fruits, vegetables and whole grain cereals are the main sources of dietary fibre, Dietary fibre is a substance mainly found in the cell wall of plant cells. It does not provide us with energy. It cannot be digested or absorbed by our bodies. However, it is important for keeping us healthy. Do you know why? ‘ruts and vegetables cereals 12.40 Foods rich in dietary fibre Food in the intestine is pushed forwards by the contraction of muscles in the intestinal wall. This is called peristalsis. As dietary fibre cannot be digested, it adds bulk to food and stimulates peristalsis, Dietary fibre also holds water which keeps faeces soft so that they can be passed out of the body easily. This helps prevent constipation. muscles contract food intestine + z 12.11 Peristalsis along the intestine * Vitamins and minerals are essential for maintaining the normal functions of our bodies. © Dietary fibre stimulates peristalsis in the prevent constip: testine and helps digest fe absorb constipation JE 13,@ TE A Healthy Body B Building blocks of carbohydrates, lipids and proteins Starch, lipids and proteins are large and complex molecules. They are made up of small molecules joined together like building blocks. 1. Building blocks of carbohydrates Complex carbohydrates are made up of simple carbohydrates. For example, starch is a complex carbohydrate. It is made up of many molecules of glucose, a simple carbohydrate. eo @e eo -— e@ glucose starch m xs 3 m 2 2 ° 2 Fig. 12.12 A starch molecule is made up of many glucose molecules. 2. Building blocks of lipids The main type of lipids in our diet is triglyceride, which include fats and oils. Each triglyceride molecule is made up of one glycerol molecule joined to three fatty acid molecules. ==» | —- SSE ERERAGERRAES ‘glycerol 3fatty acids tiglyceride Fig. 12.13 A triglyceride molecule is made up of one glycerol molecule and three fatty ‘acid molecules. There are two main types of fatty acids: saturated fatty acids and unsaturated fatty acids, Fats are mostly made up of saturated fatty acids and oils are mostly made up of unsaturated fatty acids. wilycetide #2805 sured arty acid ERE ‘lycerol Hi unsaturated foty acid 7RHERIERAABS 14 tanyaca memeaminoadé EER Q@ Allanswers OD TE er Different types of lipids ‘There are different types of lipids. Triglycerides are the main type of lipids in our diet. They are the energy stores in our bodies. Cholesterol is another type of lipids, which is an essential component of cell membranes. 3. Building blocks of proteins Proteins are made up of amino acids. The proteins in our bodies are made up of 20 different types of amino acids. They are joined together in different sequences to form many different proteins. This r 10 using the 26 letters of the English alphabet to form a large number of different words m 3 nm 2 2 ° 2 15 ‘amino acids protein Fig. 12.14 Protein is made up of amino acids. Carbohydrates, lipids and proteins are made up of small molecules joined together like building blocks. rene ees carbohydrate (starch) Qa lipid (triglyceride) Q protein Q chokesteo! RENEE@ TE AHealthy Body The importance of water to our bodies Fite en lve fo several wes In addition to the six types of food substances, we must also take in | Inman dove wttearnetee water, Water makes up about 70% of our body mass. Water has many important functions in the body. * Water is the main component of the cytoplasm of cells. It provides a medium for chemical reactions to take place in body cells. component of blood, which transports substances around the body. * Water which leave the body in solution form, such as urine and sweat. a solvent for wastes * Water makes up body secretions, e.g, digestive juices. * Water helps regulate our body temperature through the evaporation of sweat. Fig. 12.15 The functions of water in the body Our body loses water through urination, sweating and breathing out. This water loss must be replaced by drinking six to eight glasses (1 glass = 250 cm*) of water every day. We can also obtain water from other drinks such as milk, juice, tea or soup. We may suffer from poor digestion and constipation if we do not drink enough water. 12.16 Wemust drink ‘enough water every day to Seema Water has many important functions in our body. secretion 8% ination $i 16Q@ Allanswers OD TE The six main types of food substances and water all have important functions in the body. These are summarized in Fig. 12.17. Carbohydrates Lipids Proteins provide energy store energy, keep warm, build body tissues for protect organs and ‘growth and repair ‘make up cell membranes Vitamins and Minerals aa Water ‘maintain a healthy body by Dietary fire) is the main component of regulating metabolism and stimulates peristalsis and cytoplasm, blood, body strengthening immunity prevents constipation secretions, sweat and urine 12.17 Functions of the six main types of food substances end water ° 7 Checkpoint 12.1 — Write ‘T’ for a true statement and ‘F’ fora false statement. (a) Fat and oil are two types of carbohydrates. (b) Lipids stored under the skin can keep us warm. Co) itamins are a source of energy for our bodies. [a @) Amino acids are the building blocks of proteins. QaaeM (©) We must drink at least three litres of water every day. 9 7@ TE © Allanswers AHealthy Body D Food tests We have learned about different food substances and their functions. Now let us carry out food tests to test for the presence of glucose, starch, lipids, proteins and vitamin C. Experiment video Fes glucose test paper glucose solution dropper 2 distilled water spot plate Procedure 1. Observe the test end of a piece of glucose test paper. eo 2. Add one to two drops of glucose solution to a welll on a spot plate. What colour is it? 3. Dip the test end of the glucose test paper into the glucose solution and then take the paper out. Wait for 30 seconds. 4. Compare the colour of the test end of the paper with the colour chart on the bottle of glucose test paper. [> Ti Is there any colour change? 7 ‘The colour changes in glucose test paper of diferent brands D Yes/no. The test end of glucose test paper —___ ay Be efferent elec reer ao Q the colour chart on the bottle. 5. Take anew piece of glucose test paper. Repeat Steps 2 to 4 with distilled water instead of glucose solution. This acts as a control to show that the result in Step 4 is due to the presence of glucose. Is there any colour change in this case? __C_ foodtest 40308 18