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Lecture 6 - (long chains of amino acids to shorter chains o...

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Gastrointestinal System Complex polymers to simple nutrients Absorb nutrients with maximal efficiency Exclude anti-nutrients (bacteria, toxins, etc.) Food passing GI system is not “in” your body (English Channel) GI system accomplishes digestive process by: o Liquification-turn food into a watery solution so that enzymes break chemical bonds o In the mouth- liquification and mechanical disruption. Not necessary but speeds up the process. Salivary amylase begins digesting starches to simple sugars. o Food in mouth causes cells in stomach to produce hydrochloric acid (HCl) and muscles in stomach contract. HCl lowers pH of food from 7 to about 2. Kills bacteria, inactivates enzymes Low pH denatures proteins and unwind to disrupt 3D structure Activates pepsin: enzyme in the stomach that slices proteins
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Unformatted text preview: (long chains of amino acids) to shorter chains o Stomach muscle action mixes and emulsifies fats o large drops to small droplets that stay dissolved. o Exit of food from stomach to small intestine controlled by pylorous (pyloric sphincter) Exit of food SLOWED BY: 1. fiber and/or fat in the diet 2. Stress • In small intestine, sodium bicarbonate (baking soda) from pancreas neutralizes stomach acid and brings mixture to neutral pH • Bile (made in liver, stored in gall bladder) coats fat droplets and keeps them from re-forming large drops • Specialized fat-digesting enzymes called lipases digest fats • Bile absorbed and recycled back to the liver • Starch is digested by pancreatic amylase to simple sugars. • Protein molecules digested to amino acids by proteases...
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