Green - Digestion Of Lipids Flashcards
Rare inherited disorder in which a person does not make beta-lipoproteins and thus cannot absorb dietary fats, cholesterol, and fat-soluble vitamins
Abetalipopproteinemia
Non-enzymatic protein required for digestion of triglycerides
Colipase
Diarrhea caused by infection w/ bacteria or viruses that leads to loss of enterocytes
Inflammatory/infectious diarrhea
Major mechanism for re-esterifying digested triglycerides in enterocytes
Monoglyceride acylation pathway
Diarrhea caused by the presence of unabsorbable solutes in the intestines
Osmotic diarrhea
Secondary mechanism for re-esterifying digested triglycerides in enterocytes
Phosphatidic acid pathway
Diarrhea caused by infection w/ bacteria which secrete toxins that increase secretion by intestinal cells
Secretory diarrhea
Fat in feces
Steatorrhea
Gastric lipase hydrolyzes triglycerides to ?
Diglycerides and free fatty acids
Explain the process of lipid digestion in the stomach
The stomach mixing breaks lipids into droplets to increase surface area
Low pH inhibits complete emulsification
Gastric lipase breaks triglycerides to diglycerides and free fatty acids
CCK slows gastric emptying to allow time for digestion in duodenum
Complete emulsification of fats requires what pH?
Neutral or slightly alkaline
Pancreatic enzymes hydrolyze lipids to : (x4)
Fatty acids
Monoglycerides
Lysophospholipids
Cholesterol
What are 3 pancreatic enzymes involved in the hydrolysis of lipids in the small intestine?
Pancreatic lipase
Cholesterol ester hydrolase
Phospholipase A2
Cleaves fatty acid from position 1 and 3, leaving 2 fatty acids and 2-monoglyceride
Pancreatic lipase
Cleaves fatty acid from cholesterol esters, leaving free cholesterol and fatty acid
Cholesterol ester hydrolase
Releases fatty acid from position 2 of phospholipids, yielding lysophospholipids and free fatty acid
Phospholipase A2
Non-enzymatic protein secreted as inactive form by pancreas
Prevents inhibition of pancreatic lipase by bile salts
Acts as an anchor for lipase binding enzyme to bile salts of surface of droplet of emulsifieed triglyceride
1:1 ratio w/ lipase
Also binds bile salt micelle, keeping it close ot site of hydrolysis
Colipase
Chylomicrons are transported out of enterocyte via?
Exocytosis
Where do chylomicrons enter when they leave the enterocytes/
Lacteals
Thru gaps between endothelial cells lining lymphatics
What makes up a chylomicron?
Core; triglycerides, esterified cholesterol, fat soluble vitamins
Surface; phospholipids, apoprotein, free cholesterol
Chylomicrons reach the blood stream via ________
Thoracic duct
Excretion of more than 7g fat/day in feces
Lipid malabsorption
What happens when you have lipid malabsorption due to the inability to digest fats?
The pancreatic enzymes are either not secreted or inactivated due to low pH
Occurs in pancreatitis, pancreatic carcinoma, and cystic fibrosis
What can cause malabsorption due to the absence of bile salts?
Hepatic failure
Cholelithiasis
Bacteria or acids cause bile salts to not work
What are 4 ways that you can get lipid malabsorption?
Absence of bile salts
Failure to digest fat (lack of pancreatic enzyme)
Conditions that affect or decrease the number of absorbing cells
Failure to synthesize apoproteins
Explain gluten sprue/gluten enteropathy
Pt has allergic rxn to gluten.
As a result, loss of villi in small intestine
Malabsorption of fats, proteins, and carbohydrates
Treat w/ gluten free diet
_______ cells use Na-Cl cotransport mechanism to bring Cl- into cell against Cl- gradient
Na-K ATPase keeps intracellular [Na] low
Crypt cells
What type of cotransporters do crypt cells use to get Cl- inside from the blood? (In order to secrete water)
2Cl- Na K+ cotransporter
What does intestinal secretion of water do?
It assists in processes of digestion and absorption by maintaining liquidity of the cyme in small intestine
Explain the process of H2O secretion in the small intestine (to keep chyme liquidity up for digestion and absorption)
Crypt cells have 2Cl Na K cotransporters on their basolateral membranes to bring Cl into cell. Then, there are Cl channels on the apical membrane which are stimulated by GI hormones and neurotransmitters. Cl- enters lumen. Na+ follows. Water follows to maintain isotonicity.
The Cl- channels in the apical membrane are activated by increase in _________ or _____ levels
Ca++ CAMP
This is for water movement into lumen ))
Defined as excretion of 200g or more of H2O in stools of adult during 24 hour period
Diarrhea
What is the pathophysiology of osmotic diarrhea?
There’s an accumulation of nonreabsorbable substances in the small intestine. This causes an osmotic imbalance, so water follows. There is then too much water to be reabsorbed in the large intestine
Explain what happens in secretory diarrhea
Caused by infection by certain bacteria (V. Cholerae or E. Coli) or some tumors.
The Cl- channels in the small intestine are activated. Cl- enters lumen
Na and H2O follow (can lose liters of water and salt per day)
Na absorption w/ Cl- is inhibited but w/ glucose is intact
Causes of secretory diarrhea?
Infection of intestine by bacteria
Certain tumors
How does oral rehydration therapy work?
Patient’s with secretory diarrhea’s Na-Glucose cotransporters still work. So give them water w/ salt and glucose in it and you can improve the Na gradient so that water will be absorbed
What are the roles of colonic flora? (X4)
Digest carbohydrates
Make secondary bile acids
Generate short chain fatty acids
Limit invasion of pathogenic microorganisms
3 sources of intestinal gas are?
Swallowed air
Gas diffusion from bloodstream
Gas created by bacterial action in ileum and colon
