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17 Cards in this Set
- Front
- Back
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What are bile salts and bile acids?
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Amphipathic compounds, synthesized in liver and secreted via gall bladder into lumen
Bile acids compounded with a cation (Na+) |
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Describe the process for the release of bile salt?
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Chyme released into duodenum stimulates secretin and CCK release
Secretin stimulates pancreas to form fluid high in bicarb CCK stimulates pancreas to produce fluid high in enzyme and causes contraction of gall bladder Bicard and bile salts neutralize chyme Lipid is emulsified by bile salt in SI |
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What is the purpose for colipase?
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Pancreatic lipase is inactivated in presence of bile salts, which coat the substrate
Colipase binds to lipid and to the lipase, relieving the bile salt inhibition and allowing lipid to enter active site of the lipase |
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What is the action of pancreatic lipase?
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Specific for positions 1 and 3 of glycerol, converting triglyceride to 2-monoacylglycerol and free fatty acids
An isomerase converts 2-monoacylglycerol to 1-monoglyceride which can be hydrolyzed by pancreatic lipase to glycerol and free fatty acid |
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What is the action of cholesterol esterase and phospholipase A2?
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Cholesterol esterase: hydrolyze cholesterol esters
Phospholipase A2: partially hydrolyze dietary phospholipids |
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What are micelles?
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Microdroplets that are emulsified by bile salts, in which the concentration needs to be above the critical micelle concentration
Fatty acids and 2-MG are packaged into micelles with bile salts |
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What is the purpose for micelles?
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Mediate the transport of lipid digest through the aqueous environment of the gut lumen to the brush border of the enterocytes
Short chain fatty acids (14-C or less) can diffuse across the enterocyte membrane in the absence of micelle formation |
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How are lipids absorbed into epithelial cells of the brush border microvilli?
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Diffusion, bile salts are left behind in the lumen
Bile salts reabsorbed in distal intestine and returned to liver via enterohepatic circulation Glycerol and medium chain fatty acids have high water solubility and pass through the mucosa into portal circulation, transported to liver bound to serum albumin |
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How are the different types of lipid transformed in the mucosa?
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Long chain FA form acyl CoA in ATP rxn catalyzed by acyl CoA synthetase
2-monoacylglycerol reacted with acyl CoA to reform TG Cholesterol converted to cholesterol esters Phospholipid components converted back to phospholipids |
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What happens to lipids after they accumulate and are transferred into the cisterni of smooth ER?
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Protein is added to the lipid to form chylomicrons
Composed mainly of triacylglycerols, with apo B48 |
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What happens in A-beta lipoproteinemia?
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Absorbed lipids have inability to be incorporated into chylomicrons
Leads to steatorrhea |
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Where do chylomicrons go after leaving the intestinal mucosa?
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Extruded into lymphatic system and pass through the thoracic duct into the circulation
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What does the body do with plant sterol?
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Less than 5% dietary plant sterol absorbed
ATP binding cassette transporter pumps plant sterol and some cholesterol out of intestinal cells into lumen Preferentially removed by secretion into bile |
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What is chylomicron retention disease?
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Inherited disorder that affects absorption of fats, cholesterol, and certain fat-soluble vitamins
Lack of chylomicron transport |
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What situations could cause malabsorption of products of lipid digestion?
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Decreased absorption by mucosa
Impaired chylomicron formation Impaired chylomicron transport |
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What situations can cause maldigestion of products of lipid digestion?
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Impaired micelle formation
Impaired lipolysis |
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What can be used to treat maldigestion and malabsorption?
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Use of medium chain triglycerides
More soluble Hydrolyzed by pancreatic lipase and gastric lipase rapidly Rapid absorption and pass directly into blood |
