Nutrition in humans

Name: __________________ Topic: Nutrition in humans Concepts Summary Notes Nan Hua High School Biology 1 LO: Describe the functions of main regions of the alimentary canal and the associated organs: mouth, salivary glands, oesophagus, stomach, duodenum, pancreas, gall bladder, liver, ileum, colon, rectum, anus, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate  Ingestion: food taken into the body  Digestion: large, insoluble molecules are broken down to small, soluble molecules for absorption into body cells o Physical process which involves mechanical break up of food into smaller pieces through chewing o Chemical process which involves the breaking of bonds in molecules which involves enzymes  Absorption: Products of digestion such as glucose and amino acids will be taken into the bloodstream through the wall of ileum of the small intestine by processes active transport and diffusion  Assimilation: Uptake of absorbed food substances into cells and tissues to be converted into new protoplasm or used to release energy (liver)  Egestion: removal of undigested material Mouth (Ingestion, digestion) ● Chewing action of teeth breaks up food into small particles to increase surface area to volume ratio (Physical digestion) ● Tongue mixes food with saliva ● Salivary glands secrete saliva to soften the food

Name: __________________ Topic: Nutrition in humans Concepts Summary Notes Nan Hua High School Biology 2 ● Saliva contains salivary amylase to digest starch to maltose. (Chemical digestion) ● Optimal pH of salivary amylase is pH 7. Oesophagus (some digestion in the bolus) ● Long narrow muscular tube, made up of longitudinal and circular muscles ● Circular muscles constricts the lumen while the longitudinal muscles shortens the oesophagus ● Both sets of muscles work antagonistically (contract and relax alternately) to produce slow wave-like contractions that push the food down the oesophagus and the process is known as peristalsis. ● Starch digestion by salivary amylase in the bolus of food continues here and no enzymes are secreted here. Stomach (Digestion) ● Thick, muscular bag ● Peristalsis in the stomach churns, breaks up and mixes the food well with gastric juice ● Stomach wall secretes gastric juice (Dilute hydrochloric acid, pepsinogen, prorennin) ● Pepsin digest proteins into polypeptides ● Optimum pH of pepsin is pH 2 ● Hydrochloric acid o Denatures salivary amylase o Activates pepsinogen into pepsin, prorennin into rennin (to curdle milk for digestion) o Provide acidic medium for optimal action of gastric enzymes o Kills harmful microorganisms such as bacteria ● Storage of food, where the partly digested food particles becomes liquefied chyme. Duodenum (first part of small intestine) (Digestion) ● Peristalsis to churn, break up and mix the food well with digestive juices ● Receives bile (produced by liver, stored in gall bladder) via bile duct o Bile has no enzymes, so it cannot digest food. o Bile salt speeds up fat digestion by lipase by emulsification of fats into small fat globules, which increase surface area for lipase to act on. ● Secretes intestinal juice (Sucrase, Maltase, Lactase, Enterokinase, Erepsin, Lipase) ● Receives pancreatic juice (amylase, lipase, trypsinogen) from pancreas via pancreatic duct. ● Complete digestion of carbohydrates, proteins and fats takes place

Name: __________________ Topic: Nutrition in humans Concepts Summary Notes Nan Hua High School Biology 3 Ileum (last part of small intestine) (Absorption) ● Mainly for absorption ● Walls have numerous folds to provide a larger surface area for faster absorption of digested food substances. ● Villi walls are one-cell thick epithelial cells to decrease distance to allow for faster absorption of digested food substances. ● Epithelial cells have microvilli to increase surface area to volume ratio for faster absorption of digested food substances. ● Each villus is richly supplied with blood capillaries and lymphatic capillaries/lacteals to carry away quickly the absorbed food substances to maintain a steep concentration gradient. o Lacteals absorb and transport fats. o Blood capillaries absorb and transport glucose and amino acids away from the small intestine. ● Small intestine is long to provide sufficient time for more absorption of digested food substances. Colon (Large intestine) ● No digestion takes place ● Absorbs water, vitamins and dissolved mineral salts from the undigested food and the remaining undigested matter is known as faeces. Rectum ● Rectum stores faeces temporarily ● Rectum muscles would contract to expel faeces through the anus - process is known as egestion.

Name: __________________ Topic: Nutrition in humans Concepts Summary Notes Nan Hua High School Biology 4 LO: Describe peristalsis in terms of rhythmic wave -like contractions o f the muscles to mix and propel the contents of the alimentary canal ● Peristalsis is the rhythmic wave-like contractions of muscles. ● Circular and longitudinal muscles work antagonistically (one contracts and the other relaxes) ● Eg; Circular muscles contract, longitudinal muscles relax, wall of oesophagus constricts, becomes narrower and longer and push the food forward.

Name: __________________ Topic: Nutrition in humans Concepts Summary Notes Nan Hua High School Biology 5 LO: Describe the functions of enzymes (e.g. amylase, maltase, protease, lipase) in digestion, listing the substrates and end-products Organ Substrate Enzyme Products mouth starch salivary amylase maltose stomach proteins pepsin polypeptides * cow’s stomach soluble caseinogen rennin insoluble casein (milk protein) duodenum starch pancreatic amylase (from pancreatic juice) maltose fats pancreatic lipase (from pancreatic juice) fatty acids + glycerol proteins trypsin (from pancreatic juice) polypeptides Trypsinogen (inactive) enterokinase (from intestinal juice) trypsin (active) polypeptides erepsin (peptidase) (from intestinal juice) amino acids fats intestinal lipase (from intestinal juice) fatty acids +glycerol lactose lactase (from intestinal juice) galactose + glucose maltose maltase (from intestinal juice) glucose + glucose sucrose sucrose (from intestinal juice) fructose + glucose

Name: __________________ Topic: Nutrition in humans Concepts Summary Notes Nan Hua High School Biology 6 LO: Describe the structure of a villus and its role, including the role of capillaries and lacteals in absorption ● Each villus has numerous microvilli to increase surface area to volume ratio for faster absorption of digested food. ● Villus wall is one-cell thick