HUN3224 Intermediary Metabolism I Fall 2014 FINAL EXAM REVIEW r e p p U r e w o L 2 I Digestion and Absorption A Physiology of GI Tract 1 Mouth Mastication release of saliva from 3 pairs of salivary glands Chewing breaks down food and allows hydrolysis with the saliva Enzymes salivary amylase CHO lingual lipases FAT lysozymes 2 Esophagus peristalsis Muscular tube that connects the back of the mouth with the stomach movement of food via o Upper portion has striated muscle voluntary swallow action o Distal portion lacks voluntary control Ends at the lower esophageal sphincter LES a circular muscular valve 3 Stomach J shaped organ that holds food and allows for mechanical mixing and breaking down food Absorption of water alcohol fat soluble drugs aspirin and a few minerals Longitudinal oblique and circular mixing churning of foods muscles 5 regions cardia fundus body antrum pylorus 3 gastric glands o Cardiac mucus cells o Oxyntic parietal cells HCl intrinsic factor o Pyloric chief cells endocrine 4 Small Intestine pepsinogens gastric lipase gastrain into 3 portions duodenum jejunum and ileum Primary site of digestions and absorption separated absorption Folds maximize surface area to increase nutrient the intestinal cells Digestion occurs in the lumen brush border and within 5 Large Intestine colon fecal matter Absorption of water and electrolytes as well as stores Secretes copious amounts of nutrients Contains 400 species of bacteria 6 Accessory organs a Liver bile formed detoxifies blood b Pancreas digestive enzymes produced by acinar exocrine cells pancreatic juice metabolic hormones o Pancreatic juice bicarbonate enzymes electrolytes somatostatin and peptide YY o Secretions regulated by CCK and secretin o Proteolytic enzymes trypsinogen chymotripsinogen proteolastase procarboxypeptidases A B o Lipolytic lipase phospholipase A nonspecific esterase o Amylolytic amylase 3 c Gall bladder stores and concentrates bile d Salivary Glands in the oral cavity see Mouth above B Absorption Overall Nutrients entering the vascular system portal vein monosaccharides amino acids glycerol short chain Fas Lymphatic system only takes up TAGs as a part of chylomicrons through the lacteals Duodenum of small intestine is where the majority of nutrient absorption occurs Water electrolytes and small traces of nutrients not previously absorbed are taken up in the large intestine o 400 species of bacteria act on nutrients to form gases CO2 methane hydrogen C Carbohydrate Digestion Absorption o Some are reassembled to short chain fatty acids 1 Digestion large intestine Occurs in the mouth small intestine and 1 Mouth salivary amylase uses amylose amylopectin to cleave 1 4 linkages only down later into maltriose and maltose amylopectin also has 1 6 linkages that are broken denatured by pH 2 SKIPS STOMACH salivary amylase 3 Small intestine lumen there is the 1 4 linkages hydrolysis of starch to dextrin maltose maltotriose via pancreatic amylase only 4 Small intestine brush border the oligosaccharides are hydrolyzed to products monosaccharaides the enzymes are inhibited by the monosaccharide end Lactose glucose galactose Sucrose glucose fructose maltotriose Maltose glucose glucose Dextrin glucose maltose absorb water nutrients 5 Large intestine bacteria continues to further breakdown waste in order to Synthesis of and release of digestive enzymes o Sight and smell can initiate release of saliva from salivary glands via parasympathetic denatured by the low pH from HCl o Pancreatic amylases are inhibited by the end products o Salivary amylase stays with the bolus down the esophagus into the stomach where it is Regulation of GI motility o CCK released in the presence of glucose that inhibits gastric emptying and motility gastric emptying and motility Intestinal motility increased by hormone motilin inhibited by peptide YY and secretin o Glucose dependent insulinotropic peptidic GIP released by presence of glucose and inhibits o 2 Absorption 4 Carbohydrates are absorbed as their monosaccharide subcomponents glucose galactose or fructose Transport mechanism o Glucose and galactose in the presence of Na can cross apical membrane via facilitated diffusion with SGLT 1 sodium glucose transport o GLUT 2 is used for glucose and galactose when Na not readily available to enter the cell from the lumen enters the bloodstream via GLUT 2 also o Fructose uses GLUT 5 to be transported into the cell but uses GLUT 2 to enter blood o When blood glucose lumen insulin stimulates GLUT 2 to the baso lateral membrane to D Lipid Digestion Absorption decrease the absorption of glucose galactose from the lumen 1 Digestion Occurs in the mouth stomach and small intestine 1 Mouth lingual lipase is secreted by the serious glands in the back of the mouth tongue to break down milk fat increases with age and very helpful for babies 2 Stomach lingual lipase continues down to the stomach and remains active with gastric lipase from chief cells for limited hydrolysis 3 Small intestine enzymes pancreatic lipase is secreted into the lumen to hydrolyze TAGs cholesterifase cleaves a fatty acid from cholesterol phospholipase cleaves 1 fatty acid from lecithin the main phospholipid in the body to create lysolecithin co lipase is secreted from the pancreas as proco lipase and is activated by trypsin to prevent the inhibitory effect of bile salts on TAGs for lipase 4 Small intestine emulsification bile is synthesized in the liver and stored in the gallbladder before being released to the lumen to adhere to TAGs to cause an increase in SA to allow for lipases to reach the bonded of the glycerol and fatty acids 5 Small intestine enterocyte level micelles transport hydrophobic end products across brush border into enterocytes Pancreatic and bile secretions for all nutrients are regulated by CCK secretin somatostatin and peptide YY o CCK is released by presence of intraluminal fats glucose and a few amino acids o Secretin is released by increase presence of intraluminal H ions from the acidic chyme to stimulate release of bicarbonate from pancreas to balance the pH o Somatostatin is released from delta cells of pancreas as an inhibitory factor for digestion increases gastric emptying and decreases smooth muscle contraction and pancreatic releases Fats are the slowest to be digested and absorbed due to their presence increase release of CCK and secretin causing gastric emptying delays 5 o Bile is composed of water bile salts phospholipids unesterified
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