2.3 Digestion of Lipids Flashcards
Fat digestion occurs where?
Small Intestine
Know the five roles lipids play in our diet
Energy Source
Increase Texture and palatability of foods
Solubilization and dispersion of flavors
Slow gastric emptying
Essential fatty acids and fat-soluble vitamins
90% of dietary lipids are what in what form?
Triacylglycerols
What enzyme is found in the mouth that begins emulsification with dietary phospholipids but is not very significant..
Lingual Lipase
What lipid enzyme is found in the stomach?
Gastric Lipase
What enzyme is used for only short and medium chain FA
Gastric Lipase
What is the optimal pH for gastric lipase
pH 7
Why is the optimal pH significant for gastric lipase?
Only babies have pH 7 in their stomachs. Therefore, gastric lipase is active in these individuals rather than adults
Bile acids are derivatives of what other molecule?
Cholesterol
Name the three specific bile acids that are cholesterol derivatives
Cholic Acid (Add H+) Glycocholic Acid (add Glycine) Taurocholic Acid (add Taurine)
Where is Bile synthesized and stored?
Synthesized in the liver
Stored in the Gallbladder
What must happen to lipids before they can be digested by intestinal enzymes
They must be emulsified
What is the enterohepatic cycle?
Most bile salts are reabsorbed in small intestine and returned to liver via the portal vein
Where is Cholecystokinin released from and is released in response to what?
Released from jejunum in response to chyme in the duodenum
Cholecystokinin stimulates what three things?
Stimulates gall bladder to release bile into small intestine
Stimulates pancreas to release digestive enzymes
Stimulates stomach to slow down
Where is secretin released and in response to what stimulation?
Released in duodenum in response to low pH of the chyme entering the intestine
What is the function of Secretin
To tell pancreas to release a bicarbonate solution to increase pH and neutralize the pH of chyme so that it is not so acidic
Name the three pancreatic digestive enzymes
Pancreatic Lipase
Cholesteryl Esterase
Phospholipase A2
Function of Pancreatic Lipase
Converts TAGS into 2 monoacylglycerol and FFA
Can we absorb monoacylglycerols?
Yes but not Triacylglycerols. THey must be broken down first by pancreatic lipase
Function of Colipase
To help stabalize interface between water and fat for pancreatic lipase to function
Function of Cholesteryl Esterase
Degrade cholesterol esters to FFA and Cholesterol
Is cholesterol an essential nutrient?
No, cholesterol is synthesized in the liver in large quantities
Function of Phospholipase A2
Part of the process to remove the 2 FA from phospholipids
What activates phospholipase A2?
Trypsin
What is the inactivated form of colipase
Procolipase
What activates Procolipase
Trypsin
What are the two products when Procolipase is activated?
Colipase and Enterostatin
Function of Enterostatin?
Cleaved from procolipase it ahas an activity as a satiety signal.
Phospholipiase A2 removes a fatty acid from what carbon first? This leaves what product?
C2 (middle carbon)
Product is lysophospholipid
What enzyme removes the remaining FA at C1 on Lysophospholipid?
Lysophospholipase
What is the final product after Phospholipase A2 and Lysophospholipase have cleaved the two FA from C2 and C1 respectively?
Glycerylphosphorylbase
Role of FABP2/I-FABP
To sequester and bind FFA within the intestinal cell
What enzyme repackages Cholesterol Esters and Triacylglycerols within the intestinal cell?
Acyltransferase
Role of Fatty Acyl CoA Synthetase?
TO add a CoA to a Free Fatty acid within the intestinal cell to trap it in the cell.
Fatty Acyl CoA are the substrates for repacking cholesteryl ester and TAGs
T or F, Short and Medium chain FA do not require micelles for absorption. They travel to the liver via portal blood attached to albumin.
True
What are the three primary breakdown products of lipid digestion?
FFA
Cholesterol
Monoacylglycerol
