Human Nutrition IGCSE Biology Past Paper PDF 2024

BY CELL :00201110983031 00201110983031 [email protected]  1. Describe what is meant by a balanced diet 2. State the principal dietary sources and describe 3. the importance of: 4. (a) carbohydrates 5. (b) fats and oils 6...

BY CELL :00201110983031 00201110983031 [email protected]  1. Describe what is meant by a balanced diet 2. State the principal dietary sources and describe 3. the importance of: 4. (a) carbohydrates 5. (b) fats and oils 6. (c) proteins 7. (d) vitamins, limited to C and D 8. (e) mineral ions, limited to calcium and iron 9. (f) fibre (roughage) (g) water 10. State the causes of scurvy and rickets 11. Identify in diagrams and images the main organsof the digestive system, limited to: (a) alimentary canal: mouth, oesophagus,stomach, small intestine (duodenum and ileum) and large intestine (colon, rectum,anus) (b) associated organs: salivary glands, pancreas,liver and gall bladder 12. Describe the functions of the organs of the digestive system listed in 7.2.1, in relation to: (a) ingestion – the taking of substances, e.g. food and drink, into the body (b) digestion – the breakdown of food (c) absorption – the movement of nutrients from the intestines into the blood (d) assimilation – uptake and use of nutrients by cells (e) egestion – the removal of undigested food from the body as faeces CELL :00201110983031 00201110983031 [email protected]  The digestive system: includes the alimentary canal, salivary glands, liver & pancreas. Important process in human digestion INGESTION Taking in substances as food &drinks into the alimentary canal through mouth DIGESTION Breakdown of large insoluble food Molecule into smaller soluble one that can be absorbed into blood ABSORBTION Movement of small food molecules and ions through the wall of the intestine into the blood EGESTION The passing out of the food that has not been digested through the anus. Assimilation Movement of digested food molecules into the cells of the body where they are used, becoming part of the cells. CELL :00201110983031 00201110983031 [email protected]  Types of digestion PHYSICAL DIGESTION (MECHANICAL) Breakdown of food into smaller pieces without chemical change to the food molecules, to increase the surface area for chemical digestion. Ex: 1. Teeth: bite, chop and grind food into smaller pieces. 2- Stomach: churning food by contraction& relaxation. 3- Emulsification: breaking down of large fat droplets into smaller ones by bile juice. CHEMICAL DIGESTION Breakdown of large insoluble molecules into small soluble ones by using enzymes, including break down of bonds (hydrolysis) Stages of digestion IN MOUTH.1 A. PHYSICAL DIGESTION BY TEETH STRUCTURE OF THE TEETH CELL :00201110983031 00201110983031 [email protected] Enamel - It is the outer layer of the tooth - It is the hardest substance made by the body - Can be dissolved by acids 2. Dentine - Living regions contains channels of cytoplasm. - It is quite hard but not as hard as enamel. 3. Pulp (cavity) - Contains nerves for sensation - Contains blood vessels to supply food and oxygen. - Contains cells which make dentine. 4. Cement - It is a bone-like substance. - Have fibres growing out of it to attach the tooth to the jaw bone, and to allow the tooth to move slightly. CELL :00201110983031 00201110983031 [email protected]  Types of teeth Have sharp edges Are more pointed Are four in each Larger and for cutting and to tear food jaw, two in each broader biting of food -Are two in every side than premolars - Found in the jaw - Each has one or - Each has four front of the two cusps and roots or more mouth - Broad fo grinding cusps Four in each jaw and crushing food - Used of crushing and grinding Wisdom teeth - Are the teeth found at the back of the jaw. - Are so called because they grow later than others. General functions of teeth 1. Help with the ingestion and physical digestion of food. 2. Bite off pieces of food. 3. Chop, crush or grind into smaller pieces and this gives the food a larger surface area, which make it easier for the enzymes to work, and helps to dissolve the soluble parts of food, 4.It facilitates swallowing of food. CELL :00201110983031 00201110983031 [email protected]  B. chemical digestion in mouth BY USING SALIVA THAT CONTAINS WATER 1. Help in digestion 2. Dissolving food 3. Soften the food to be easier to chewed and swallowed MUCUS 1. Make chewed food in mouth bind together to form bolus. 2. Lubricates food making it easier to move down the alimentary canal. 3. Also forms a covering over the inner surface of the alimentary canal preventing enzymes& acidic juices in stomach from digesting cells. AMYLASE Digest the starch in alkaline condition and change it into maltose ESOPHAGUS The food is moved through the oesophagus by peristalsis (Waves of contraction and relaxation of muscle walls of alimentary canal to push the food forward towards the stomach.) CELL :00201110983031 00201110983031 [email protected]  DIGESTION IN STOMACH A.PHYSICAL DIGESTION by contraction and relaxation. B. CHEMICAL DIGESTION GASTRIC JUICE CONTAINS 1. Hydrochloric To kill microbes that may enter with the food To activate the enzyme pepsinogen into the active acid pepsin. 2. Pepsinogen - An inactive enzyme - It is activated by hydrochloric acid to form pepsin - Pepsin acts on proteins to be digested into polypeptides. 3. Mucus To protect the wall of the stomach against hydrochloric acid and pepsin. 1. Pepsin is secreted in an inactive form. 2. Stomach secretes a protective layer of mucus Pepsin in the stomach: Pepsin digests proteins by breaking them down into polypeptides. Trypsin in the small intestine: Breaks down proteins to polypeptides CELL :00201110983031 00201110983031 [email protected]  NOTICE The enzyme that digest proteins are known as proteases 3. Proteases are secreted in an inactive form in order not to digest the cells producing them as the cells are made of proteins 4. salivary amylase stops in the stomach as it acts in slightly alkaline. 5. Chyme: The food mixed with the gastric juice and that leaving the stomach in known as, it is acidic Small intestine Consists of two parts which are 1.DEODENUM 2.ILEUM function:.1- emulsification of fat function:.1-. complete digestion of 2- change pH of food corning from all food types. stomach from acidic to alkaline 2-Absorption of digested food CELL :00201110983031 00201110983031 [email protected]  Types Of Digested Juices in Small Intestine 1.In Duodenum Type of juice Formed in the liver - It is stored in the gall bladder - It is not necessary as an enzyme as it does not help to speed up a metabolic Reaction Components of bile 1.Bile A. Bile pigment - Formed in the liver due to the destruction of dead red blood cells. - Excreted with urine and feces giving each its characteristic color. B. Bile salts - Are used to emulsify fats (Means breaks down the large droplets of fats into smaller droplets) -contains hydrogen carbonate it is an alkali that helps neutralise acid( chyme) coming from stomach. 2.pancreatic juice Components of bile Produced in  1. Bicarbonate Reduces acidity of Chyme. pancrease 2. Amylase Breaks carbohydrates into maltose. 3. (trypsin ) Breaks proteins into polypeptides. Works in the  4. lipase Breaks fats into fatty acids and. deodenum glycerol. CELL :00201110983031 00201110983031 [email protected]  2.In Ileum Adaptation of ileum to its function It is very long, about 5m in an adult This gives plenty of time for digestion and human absorption It has villi. Each villus is covered with This gives the inner surface of the cells which have even smaller small intestine a projections on them, called very large surface area. microvilli The larger the surface area, the faster the nutrients can be absorbed. Villi contains blood capillaries Monosaccharides, amino acids, water, minerals and vitamins, and some fats, pass into blood, to be taken to the liver and then round the body Villi contains lacteals, which are part Fats are absorbed into the lacteals of the lymphatic system. Villi have walls only one cell thick The digested nutrients can easily cross the wall to reach the blood capillaries and lacteal. CELL :00201110983031 00201110983031 [email protected]  Intestinal enzymes 1. Lipase: Like the pancreatic lipase it acts on lipids to be digested into fatty acids and glycerol 2. Peptidase: Acts on polypeptides to be digested into amino acids 3. Maltase: - Acts on maltose to be digested into glucose CELL :00201110983031 00201110983031 [email protected]  Summary for digestion CELL :00201110983031 00201110983031 [email protected]  Absorption of food Bloody route Amino acids, monosaccharides, water, minerals and water-soluble vitamins: - Pass through the epithelial cells of villi into the blood capillaries. - Blood capillaries of villi join together forming a blood vessel known as hepatic portal vein - Hepatic portal vein carries the absorbed food to the liver a. To store the excess glucose in the form of glycogen b. To break down the toxic materials by a process known as detoxification c. To break down the excess amino acids by a process known as deamination producing urea. Lacteal route Fatty acids and glycerol Large intestine components Colon Absorption of water and salts Rectum Storage of feces Anus Egestion CELL :00201110983031 00201110983031 [email protected]  Important comparisons Root hair cell Villus 1. Consists of one cell only Consists of many cells 2. Has a cellulose cell wall - No cellulose cell wall 3. Found in plants 4. Contains a large sap vacuole - Found in animals 5. Contains no blood vessel - Contains no sap vacuole 6. Contains no lacteal vessel - Contains blood vessels 7. Used for absorption of water and - Contains lacteal vessel miner - Used for absorption of digested food. Functions of Liver 1. Destruction of hemoglobin of dead red blood cell to produced Iron is stored in liver Pigments are used in making bile. 2. Produces bile which is used to emulsify fats 3. Detoxification: (Means breaks down the toxic materials to be excreted with urine.) Drugs are modifies Hormones 4. Deamination (is the removal of nitrogen containing part of amino acids as urea 5. of energy from the remainder of amino acid 6. Manufacture of plasma proteins such as fibrinogen. 7. Regulation of level of glucose in blood. CELL :00201110983031 00201110983031 [email protected]  Hepatic Portal Vein Hepatic Vein 1. It joins small intestine and liver. It joins and liver and the inferior vena 2. It contains a higher concentration cava. of glucose. - It contains a lower concentration of 3. It contains a higher concentration glucose as the liver stores the excess of amino acids. glucose in the form of glycogen 4. It contains a lower concentration - It contains a lower concentration on of urea Amino acids, because the liver breaks 5. May contain toxic materials down excess amino acids by a process known as deamination. - It contains a higher concentration of urea which is formed as a result of deamination. - No toxic materials as the liver breaks down the toxic materials by a process known asdetoxification CELL :00201110983031 00201110983031 [email protected]  Some diseases that affect digestive system DIARRHEOA DEFINITION Excessive loss of watery feces CAUSES Infection by a bacteria that causes cholera. TREATMENT giving oral rehydration therapy"' drink containing water with small. amounts of salt & sugars dissolved in it. HOW TO 1-Sewage treatment PREVENT THE 2- vaccination TRANSMISSION 3- using suitable antibiotics Explain how the cholera causes dirrhoea 1. Cholera bacteria are ingested and start to multiply in the small intestine. The bacteria attache to the wall of the alimentary canal. 2. The bacteria releases toxins. 3. The toxin stimulates the lining of the intestine to secrete chloride ions, which accumulate in the lumen of the small intestine. 4. This increases the concentration of the fluid in the lumen, lowering the water potential. 5. So water move out of blood into the lumen of small intestine by osmosis. So more watery faeces cause diarrhoea. CELL :00201110983031 00201110983031 [email protected]