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2. ©1996 Norton Presentation Maker, W. W. Norton & Company The human digestive system: amylase pepsin, HCl bile (emulsifier) trypsin, amylase, H 2 CO 3 (alk), lipase subunit absorption bacterial culture unknown water reabsorption waste holding, elimination acidic portion alkaline portion

3. ©1996 Norton Presentation Maker, W. W. Norton & Company An intestinal cross section reveals the increased surface area: circular muscles for peristalsis

4. ©1996 Norton Presentation Maker, W. W. Norton & Company To increase the surface area of the absorptive regions of the intestine, the lining is corrugated and lined with villi villi

5. ©1996 Norton Presentation Maker, W. W. Norton & Company The villi of the intestine have good blood supply for nutrient uptake Notice how the villus is coated with microvilli…for more area! sugars, amino acids, nucleotides

6. ©1996 Norton Presentation Maker, W. W. Norton & Company Here you can see the microvilli from a single villus villus microvilli

7. Digestion of polysaccharides amylase Starch maltase Maltose Glucose These monosaccharides are ready for absorption from the digestive system. glu  -1,4 glycosidic bond

8. terminal AA removers dipeptide splitter Individual Amino Acids For Absorption in Small Intestine Protein digestion in mammals: HisGluTyrThrLysHisGluSerArgAspTrpThrPhe amino end carboxyl end Stomach Pancreas pepsin HisGluTyrThrLysHisGluSerArgAspTrpThrPhe HisGluTyrThrLysHisGluSerArgAspTrpThrPhe HisGluTyrThrLysHisGluSerArgAspTrpThrPhe HisGluTyrThrLysHisGluSerArgAspTrpThrPhe trypsin chymotrypsin carboxypeptidaseaminopeptidase dipeptidase Proteins are polymers of some 22 different amino acids Enzymes cleave the peptide bond during… recognize phenolic AA, cleave amino side recognize phenolic AA, cleave carboxyl side recognize basic AA, cleave carboxyl side cleave AA from amino endcleave AA from carboxyl end recognize dipeptide, cleave peptide bond

9. ©1996 Norton Presentation Maker, W. W. Norton & Company Chymotrypsinogen conversion into chymotrypsin Chymotrypsinogen from pancreas is inactive Activation by acidic pepsin cleavage Finished chymotrypsin with active site recognizing Tyr, Trp and Phe How do you make digestive enzymes without digesting yourself?

10. Summary of macromolecule digestion into subunits Disaccharides maltose sucrose lactose Monosaccharides gluose frucose galactose Polysaccharides starch (amylose) salivary amylase pancreatic amylase intestinal maltase sucrase lactase Proteins Peptides Amino Acids Endopeptidases: stomach pepsin pancreatic trypsin pancreatic chymotrypsin Exopeptidases: pancreatic intestinal Fats (triglycerides) Emulsified fats liver bile monoglycerides fatty acids glycerol direct absorption pancreatic lipase