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GRADE 11 LIFE SCIENCES SESSION 5: HUMAN NUTRION Key Concepts In this session we will focus on summarising what you need to know about: • • • The differences in dentition between herbivores, carnivores and omnivores, specifically in terms of the nutritional requirements and energy relationships Identification of the macro-structure of alimentary canal and associated organs and the functions of the different parts Processes of ingestion, digestion, absorption, assimilation and egestion Terminology & definitions Nutrition Metabolism Autotrophs • • • Intake and use of food in metabolism All chemical reactions that take place in a cell an organism which is able to produce its own organic food by photosynthesis e.g. plants Heterotrophs • an organism that is dependent on another organism for food Ingestion Digestion Absorption Assimilation • • • • Deamination Homeostasis • • Insulin • Glucagon • Diabetes Malnutrition • • Bolus Chyme Peristalsis Villus • • • • Hydrolases • intake of food (eat) large molecules of food are broken down to small molecules the small molecules are absorbed into the blood Absorbed nutrients are taken in the blood plasma to all body cells Removal of the amino group from and amino acid in the liver A series of processes by which the internal environment of the body is kept constant e.g. sugar Hormone secreted by the pancreas that converts glucose to glycogen Hormone secreted by the pancreas that converts glycogen to glucose Disease characterised by high blood sugar A physical or psychological disorder that is usually the result of a faulty or inadequate diet A ball of food particles which stick together because of saliva Partially digested, finely divided food which leaves the stomach Wavelike movement in the tubes of the alimentary canal Tiny finger like projections of the small intestine that absorb the digested food Enzymes that break down food chemically e.g. carbohydrase, proteases and lipase Key Concepts X-planation All living organisms need nutrition of some sort in order to obtain the energy and building blocks required to sustain life, growth and development. Autotrophic organisms (green plants for example) use photosynthesis to obtain their nutrients and energy, while heterotrophic organisms (e.g. humans) need to consume food in order to obtain the nutrients and energy they require. For a human being to be healthy the nutrients required must be consumed in the correct proportions and amounts –this type of diet leads to maximum health and strength, while an unbalanced diet can cause many health problems. If the incorrect proportions or amounts of nutrients are eaten for prolonged periods of time the result is malnutrition. Different teeth for different life styles • • • Different animals have different types of teeth depending what they eat. Because mammals are endothermic they need a lot of food to produce heat energy to keep their bodies warm. For this they need specialised teeth to help them digest their food properly Mammals usually have four different types of teeth: o Incisors – biting food o Canines – catching, holding, tearing or killing o The premolars and molars – crushing and grinding Herbivores • • • • Well-developed incisors –for clipping off plant material Usually No canines Premolars and molars are broad and flat for chewing There is a space in front of the premolars called the diastema. The animal pushes its tongue through this gap to sweep grass into its mouth Sheep 0:0:3:3 3:1:3:3 I C P M 32 teeth Carnivores • • • Canines long for piercing skin and tearing and killing prey. Incisors short and pointed for holding and shredding Premolars and molars have jagged edges that slice, they are called carnassial teeth Cat 3:1:3:1 3:1:2:1 I C P M 30 teeth Omnivores • • • Incisors shovel shaped for biting Canines pointed for tearing Flat molars for grinding food The Digestive System Ingestion • this is where food is taken in to the alimentary canal Digestion • • • this is where large insoluble molecules of food are broken down to small molecules digestion is physical and chemical Physical o During this process food is broken down into smaller particles to enlarge the outer surface area for enzyme action during chemical digestion. This includes chewing, bolus formation, churning movements and peristalsis. Chewing Mastication - Food is broken down in smaller pieces by the teeth and the tongue. Bolus formation After food has been chewed it is rolled into a ball, bolus, and swallowed down the pharynx into the oesophagus. Churning movements Takes place by muscular contractions in the stomach wall. Food is also mixed with the gastric juice in which digestive enzymes occur Peristalsis Muscular contractions of the wall of the alimentary canal, which develop by the contraction and relaxation of the circular and longitudinal muscles. This helps push the food through the alimentary canal. Chemical Digestion • • This is the breakdown of large insoluble molecules to smaller soluble molecules by hydrolases (enzyme) by a process called hydrolysis. During hydrolysis water id added. Substrate Carbohydrates Proteins Fats / lipids Enzyme Where is it produced? Carbohydrases In the mouth, e.g. salivary amylase pancreas and small maltase intestines sucrase lactase Proteases In the stomach and e.g.pepsin pancreas and small rennin intestine trypsin erepsin Lipase In the pancreas and small intestine End product Glucose Fructose Galactose Amino acids Glycerol and fatty acids ABSORBTION • • Digested food is now in soluble form (glucose, amino acids, glycerol and fatty acids) and is absorbed by diffusion by the villi that line the small intestine. Structure and importance of a villus - The villus is surrounded by a single thin layer of columnar epithelium for fast and easy diffusion - The villus contains many capillary blood vessels for effective uptake of nutrients - It contains a central lacteal for the uptake of fats - Goblet cells in columnar epithelial secrete mucous to dissolve digested nutrients The columnar epithelial cells have many mitochondria, which provide energy for active transport Microvilli on the columnar epithelium enlarge the absorption area Most absorption in the small intestine occurs in the jejunum. The products of digestion enter cells of the villi, move across the cells, and enter blood vessels called capillaries. Diffusion accounts for the movement of many nutrients, but active transport is responsible for the movement of glucose and amino acids. The products of fat digestion pass as small droplets of fat into lacteals, which are branches of the lymphatic system. Absorption is completed in the final part of the small intestine, the ileum. Substances that have not been digested or absorbed then pass into the large intestine. All substances that are absorbed end up passing through the liver, carried away from the gut by the hepatic portal system. THE HEPATIC PORTAL SYSTEM Once inside the blood vessels the nutrients are transported to the liver via the hepatic portal vein (part of the hepatic portal system, which includes the veins draining blood from the stomach and the intestines). In the liver many nutrients are processed before moving on to the cells of the body via the hepatic vein THE ROLE OF THE LIVER Excess Nutrients The cells of the liver remove excess glucose from the bloodstream and convert the glucose to a polymer called glycogen for storage. The liver also functions in amino acid metabolism. In a process called deamination, it converts some amino acids to compounds that can be used in energy metabolism. In doing so, the liver removes the amino groups from amino acids and uses the amino groups to produce urea. Urea is removed from the body in the urine. Fats are processed into two-carbon units that can enter the Krebs cycle for energy metabolism. The liver also stores vitamins and minerals, forms many blood proteins, synthesizes cholesterol, and produces bile for fat digestion. Toxins Alcohol, drugs and other materials that may be harmful to the human body are detoxified by the liver and rendered harmless. Other organs are responsible for the excretion of these products e.g. urea from excess amino acid metabolism is excreted by the kidneys. X-ample Questions Question 1 Study diagram 1 and answer the questions that follow 1 2 3 4 5 6 Diagram 1.: Diagram showing a part of the digestive system 1.1 Provide labels 1-6. 1.2 What is the food in the part labelled 2 known as? (1) 1 Draw a suitable graph to show the pH of the mouth, stomach, and small intestine. (6) 2 1.3 (6) 4 Study diagram 2 and answer the questions that follow. 3 1.4 Name blood vessel 1 and the valve labelled 4. (2) 5 1.5 The pancreas labelled 5 is an endocrine as well as an exocrine gland. Name one endocrine function of the pancreas. (2) 1.6 In which part would you experience heart burn? Explain what heartburn is. (1) (2) 1.7 Draw a villus and label the relevant structures. ( 2 mark drawing, 1 mark heading, 7 labels) (10)