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