PowerPoint Slides for Cambridge IGCSETM Biology Student's Book CHAPTER 7 HUMAN NUTRITION © 2021 Marshall Cavendish Education Pte Ltd The following content has not been through the Cambridge Assessment International Education endorsement process. 1 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book 7.1 Diet In this section, you will learn the following: • • • • Describe what is meant by a balanced diet. State the principal dietary sources and describe their importance. State the causes of scurvy and rickets. Describe the use of DCPIP test for vitamin C. © 2021 Marshall Cavendish Education Pte Ltd 2 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What is a balanced diet? A balanced diet contains the right amount of • carbohydrates, • fats, • proteins, • vitamins, • minerals, • water, • dietary fibre, to meet the daily requirements of the body. The child on the right has rickets, caused by a deficiency of vitamin D or calcium in her diet. © 2021 Marshall Cavendish Education Pte Ltd 3 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What is a balanced diet? Some vitamins and mineral ions Vitamin or mineral ion C (Ascorbic acid) D Function(s) Needed for synthesis of collagen, a protein needed to help wounds heal and bind the cells together Deficiency disease Scurvy: swollen bleeding gums, internal bleeding (haemorrhages) in muscles and skin, difficulty in wound healing and painful swelling of joints Promotes absorption of calcium and Rickets in children: risks of tooth phosphates from the intestines, and helps decay, bones become soft and keep teeth and bones strong pliable, and bones can bend under the body weight, resulting in bowed legs or knock knees © 2021 Marshall Cavendish Education Pte Ltd Sources Citrus fruits (lemons and oranges), papaya, bananas and green vegetables Egg yolk, liver or liver oil (cod liver oil), sardines, tuna and salmon 4 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What is a balanced diet? Some vitamins and mineral ions Vitamin or mineral ion Function(s) Deficiency disease Sources Rickets in children Osteoporosis in adults: bones become less dense and fragile, increased risks of fracture Milk, cheese, green leafy vegetables, tofu, soya beans and ikan bilis Calcium Needed for healthy bones and teeth, muscle contractions and clotting of blood • • Iron Needed for making haemoglobin, the red pigment in red blood cells that carries oxygen around the body Anaemia: the person looks pale due to lack of red blood cells and gets tired easily due to insufficient oxygen for respiration © 2021 Marshall Cavendish Education Pte Ltd Liver, egg yolk, meat and green leafy vegetables 5 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Dietary fibre or roughage • Dietary fibre such as cellulose is present in plant matter and aids in digestion. • Cellulose cannot be digested in our bodies. • This stimulates the intestinal walls to contract, in a process called peristalsis. • Peristalsis prevents constipation. © 2021 Marshall Cavendish Education Pte Ltd 6 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Let’s Investigate 7A • Fruit with the highest number of drops of juice needed to turn DCPIP colourless has the smallest vitamin C content. • The more drops of juice needed to turn DCPIP colourless, the lesser the concentration of vitamin C in the drops that fruit has the smallest vitamin C content. © 2021 Marshall Cavendish Education Pte Ltd 7 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book 7.2 Nutrition and the Human Digestive System In this section, you will learn the following: • • Identify in diagrams and images the main organs of the digestive system. Describe the functions of the organs of the digestive system in relation to ingestion, digestion, absorption, assimilation and egestion. © 2021 Marshall Cavendish Education Pte Ltd 8 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What is nutrition? Nutrition is the process by which organisms obtain food and energy for • growth, • repair, • and maintenance of the body. In humans, nutrition consists of the following processes: • Feeding or Ingestion • Digestion • Absorption • Assimilation Feeding or ingestion is the process whereby food is taken into the body © 2021 Marshall Cavendish Education Pte Ltd 9 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book The human digestive system The human digestive system consists of the alimentary canal and the organs (liver and pancreas) connected to it. The human digestive system © 2021 Marshall Cavendish Education Pte Ltd 10 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book The human digestive system 1. The mouth Food enters the body through the mouth. In the mouth there are: • teeth • salivary glands • tongue © 2021 Marshall Cavendish Education Pte Ltd 11 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book The human digestive system 2. The oesophagus The oesophagus (gullet) is a narrow, muscular tube where food passes in wave-like contractions called peristalsis. 3. The stomach The stomach is a distensible muscular bag, with thick and well-developed muscular walls. Peristalsis The stomach wall © 2021 Marshall Cavendish Education Pte Ltd 12 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book The human digestive system 4. The small intestine The small intestine consists of the U-shaped duodenum, and the much-coiled ileum. ~ 6 metres long 5. The large intestine The large intestine consists of the colon and the rectum where undigested food is stored. ~ 1.5 metres long Large intestine Small intestine © 2021 Marshall Cavendish Education Pte Ltd 13 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book The human digestive system 6. The pancreas The pancreas secretes pancreatic juice and hormones. 7. The liver The liver produces bile and is involved in assimilation of nutrients. 8. The gall bladder The gall bladder stores bile. Liver Gall bladder Pancreas © 2021 Marshall Cavendish Education Pte Ltd 14 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Let’s Practise 7.1 and 7.2 2 Figure below (Figure 7.7 on Student’s Book p. 113) shows a mass of food as it moves along the small intestine. (a) What happens to the wall of the alimentary canal at the region marked A? (b) Draw an arrow in the diagram to show the direction in which the food is moving. © 2021 Marshall Cavendish Education Pte Ltd 15 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book 7.3 Digestion in Humans In this section, you will learn the following: • • • • • • • Describe physical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules. State that physical digestion increases the surface area of food for the action of enzymes in chemical digestion. Describe the function of the stomach in physical digestion. Describe chemical digestion as the breakdown of large insoluble molecules into small soluble molecules. State the role of chemical digestion in producing small soluble molecules that can be absorbed. Describe the functions of amylase in breaking down starch, protease in breaking down protein, and lipase in breaking down fats and oils. State where these enzymes are secreted and where they act. © 2021 Marshall Cavendish Education Pte Ltd 16 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book 7.3 Digestion in Humans In this section, you will learn the following: • • • • • • • Describe the functions of hydrochloric acid in gastric juice. Describe the digestion of starch by amylase. Describe the digestion of maltose by maltase to glucose on the membranes of the epithelium lining the small intestine. Describe the digestion of proteins by pepsin in the acidic conditions of the stomach. Describe the digestion of proteins by trypsin in the alkaline conditions of the small intestine. Explain that bile is an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action. Outline the role of bile in emulsifying fats and oils to increase the surface area for the chemical digestion. © 2021 Marshall Cavendish Education Pte Ltd 17 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What is digestion? Digestion is the process whereby large food molecules are broken down into smaller, soluble molecules that can be absorbed into the body cells. • Physical digestion The mechanical breakdown of food into small pieces without any chemical change to the food molecules. • Chemical digestion The breaking down of the large molecules in food into small soluble molecules that can be absorbed. This involves chemical reactions catalysed by digestive enzymes. Chemical digestion by hydrolytic reaction © 2021 Marshall Cavendish Education Pte Ltd 18 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Processes that take place in the mouth (a) In the mouth, chewing breaks up the food and mucus softens the food. (b) Food is rolled into boli and passed down the oesophagus. Digestion begins in the mouth © 2021 Marshall Cavendish Education Pte Ltd 19 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Digestive processes that take place in the stomach 1. Gastric glands secrete gastric juice into the stomach cavity. 2. Peristalsis in the stomach wall churns and breaks up the food, and also mixes the food with gastric juice. 3. Dilute hydrochloric acid in gastric juice stops the action of salivary amylase, provides an acidic medium suitable for pepsin to work and kills certain potentially harmful microorganisms in food. 4. Pepsin in gastric juice digests proteins to short chains of amino acids. 5. The partly digested food becomes liquefied, forming chyme. 6. Chyme passes in small amounts into the duodenum when the ring of muscle at the lower part of the stomach relaxes and opens. © 2021 Marshall Cavendish Education Pte Ltd Chyme passes in small amounts into the duodenum 20 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Digestive processes that take place in the small intestine Chyme enters the small intestine. It stimulates the pancreas to secrete pancreatic juice, the gall bladder to release bile, the epithelial cells in the small intestine to produce the enzymes maltase and lipase. © 2021 Marshall Cavendish Education Pte Ltd 21 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Digestion of different foods How are carbohydrates digested? How are proteins digested? Some protein digestion begins in the stomach, where pepsin digests proteins. The undigested proteins that enter the small intestine are digested by trypsin. © 2021 Marshall Cavendish Education Pte Ltd 22 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Digestion of different foods How are fats digested? Big fat droplets are emulsified into tiny fat droplets, which are then broken down by lipase. (emulsified fats) © 2021 Marshall Cavendish Education Pte Ltd 23 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Organs and enzymes involved in digestion Region of Digestion Secretion Source Enzyme(s) Action Mouth Saliva Salivary glands Salivary amylase Starch → maltose Stomach Gastric juice Gastric glands Pepsin Proteins → polypeptides Bile Liver - Bile emulsifies fats Trypsin Proteins → polypeptides Amylase Starch → maltose Lipase Fats → fatty acids and glycerol Lipase Fats → fatty acids and glycerol Protease Polypeptides → amino acids Maltase Maltose → glucose Pancreatic juice Small intestine Intestinal enzymes © 2021 Marshall Cavendish Education Pte Ltd Pancreas Epithelial cells 24 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Let’s Practise 7.3 2 An experiment was set up as in figure as shown (Figure 7.12 in Student’s Book). The water in the beaker was covered with a thin layer of oil. When sulfur powder was sprinkled into the beaker, the powder rested on the layer of oil and did not sink. However, when a detergent (which acts like bile) was added into the beaker, the sulfur powder sank into the water. Explain what happened. © 2021 Marshall Cavendish Education Pte Ltd 25 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book 7.4 Absorption In this section, you will learn the following: • • • • • State that the small intestine is the region where nutrients are absorbed. State that most water is absorbed from the small intestine, but that some is also absorbed from the colon. Explain the significance of villi and microvilli in increasing the internal surface area of the small intestine. Describe the structure of a villus and describe the roles of capillaries and lacteals in villi. Describe the functions of the organs of the digestive system in relation to egestion. © 2021 Marshall Cavendish Education Pte Ltd 26 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book How is the small intestine adapted for absorption? The inner surface has numerous minute finger-like projections called villi, which increase the surface area for absorption. Scanning electron micrograph of the small intestine showing the villi © 2021 Marshall Cavendish Education Pte Ltd 27 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book How does absorption take place in the intestines? Villi in a portion of the small intestine © 2021 Marshall Cavendish Education Pte Ltd 28 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What happens after absorption in the small intestine? 1. Blood rich in nutrients: transported to liver. 2. Most of the absorbed sugar: converted into glycogen and stored. 3. Some glucose: distributed around body via blood leaving liver. 4. Amino acids: • Used for growth and repair by cells. • Used to form enzymes and hormones. Absorption in the colon The colon absorbs water and mineral ions into the bloodstream. © 2021 Marshall Cavendish Education Pte Ltd 29 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book 7.5 Human Dentition In this section, you will learn the following: • • Identify in diagrams and images the types of human teeth: incisors, canines, premolars and molars. Describe the structure of human teeth, their types and functions in physical digestion of food. © 2021 Marshall Cavendish Education Pte Ltd 30 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What are the types of teeth and their functions? Human skull showing the different types of teeth © 2021 Marshall Cavendish Education Pte Ltd 31 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What is the structure of the teeth? Longitudinal section of incisor and molar teeth © 2021 Marshall Cavendish Education Pte Ltd 32 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Let’s Practise 7.4 and 7.5 5 The table below (Table 7.3 in Student’s Book p. 121) shows the results of the absorption of digested food substances in the presence and absence of oxygen. By what processes are the digested food substances absorbed? Explain your answers. © 2021 Marshall Cavendish Education Pte Ltd 33 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What have you learnt? Can you draw your own mind map? © 2021 Marshall Cavendish Education Pte Ltd 34 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book What have you learnt? Can you draw your own mind map? © 2021 Marshall Cavendish Education Pte Ltd 35 PowerPoint Slides for Cambridge IGCSETM Biology Student's Book Acknowledgements • • • • • • • • • Slide 1: digestive system X-ray © Gustoimages | Science Photo Library Slide 2: balanced diet © unsplash.com (https://unsplash.com/photos/VpOpy6QrDrs) Slide 3: ricket child © Topical Press Agency | Stringer | Getty Images Slide 6: vegetables © pixabay.com (https://pixabay.com/images/id-1238252/) Slide 9: girl eating salad – ID 105605079 © Olena Yakobchuk | Dreamstime.com Slide 11: mouth © pixabay.com (https://pixabay.com/images/id-29657/) Slide 12: gastric mucosa © Astrid & Hanns-frieder Michler | Science Photo Library Slide 18: boy eating © pixabay.com (https://pixabay.com/images/id-3324316/) Slide 27: intestinal lining © Steve Gschmeissner | Science Photo Library © 2021 Marshall Cavendish Education Pte Ltd 36
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