digestion - I. Digestion, Absorption and Metabolism...

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I. Digestion, Absorption and Metabolism Background Before each cell can be nourished, food must be changed into most simple form so it can be absorbed into the blood. Then it must be transported to the cells for use. Digestion is the process of changing food into the simplest form 1. Digestive tract is a coiled tube ~30 feet that passes through the center of the body 2. Until the food passes through the digestive walls, it’s still considered to be ‘outside’ the body 3. Digestion is accomplished by a combination of mechanical and chemical changes 4. Peristalsis: churning action that propels food down the tract (Chewing and Peristalsis are mechanical changes) 5. Chemically ingested food is changed by enzymes, which are provided in the mouth, stomach, small intestine, etc. a. Enzyme: protein that is a catalyst or trigger for chemical reactions Amylase: acts on starch Protease: acts on protein Lipase: acts on lipid A. Digestion End products of digestion are: monosaccharides (CHO), amino acids (protein), fatty acids, glycerol, mono and diglycerol (fat), minerals, vitamins, and water 1. Ingestion Regulated by appetite which responds to both external and internal stimuli a. internal: drop in glucose level stimulates hunger or contractions of the stomach in the absence of food b. external: social, time, place, stress, reward
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2. Mouth a. saliva- 2 major roles 1) mixes with food, lubricates dry food, dilutes thicker foods 2) provides the starch splitting enzyme (salivary amylase) which converts complex CHO to simple CHO b. lingual lipase 1) at the base on the tongue to begin the digestion of lipids
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digestion - I. Digestion, Absorption and Metabolism...

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