Lipid Digestion FC Flashcards
Questions
Answers
What breaks down fatty acids? From what? Which positions?
Lipases
Triglycerol
From positions 1 and 3
What lipase is made in the mouth? Does it remain active in the stomach?
Lingual Lipase
Yes
Why do lipases only have limited activity without stomach churnning?
Because they can only act on the surface area of a lipid droplet
What secretes gastric lipase?
Gastric mucosa
Which lipase does most triacylglyceral hydrolysis?
Pancreatic lipase
Besides pancreatic lipase, what else is secreted by the pancreas with the lipase? What is its function?
Procolipase - proenzyme
Converted to colipase by trypsin
Colipase binds lipace to mixed micelle, prevent inhibition of lipase by bile salts
What are the two major products of lipase?
2 FFA
1 2-monoacylglycerol
What two other ezymes are released from the pancreas to aid in lipid metabolism? What is their function?
Prophospholipase A2 - converted to phospholipase A2 by trypsin, then removes FA from 2nd position, producing one FFA and one lysophosphlipid
Choslesterol esterase - hydrolyzes ester producing cholesterol and FFA
Which fatty acids do not require bile salts to be absorbed?
Short/medium chain bile salts
Which 3 proteins play a role in sterol absorption?
NPC1L1 - Niemann-Pick C1-like protein
SCARB1 - scavender receptor B-1
CD36
What happens if NPC1L1 is knocked out?
70% decrease in cholesterol absorption
What percentage of dietary cholesterol is absorbed?
30-40%
What percentage of FFA and MAGs are absorbed?
Nearly 100%
What binds with long chained fatty acids inside intestinal cells?
Fatty acid-binding protein (FAB)
Where in the cell are fatty acids converted to triacylglycerols?
ER
Which pathway contributes to most triacylglycerol synthesis? What two enzymes are used?
Monoacylglycerol Pathway
Monoacylglycerol acyltransferase and diacylgycerol acyltransferase
What is a secondary pathway for triacylglycerol synthesis? What enzyme is used first? Which enzyme can be used from the monoacylglycerol pathway and when?
Phosphatidic acid pathway
Glycerol kinase
Diacylglycerol acyltransferase - adds 3rd acyl after the phosphate group has been removed from 3rd position
What are the two components of a chylomicron? Where are chylomicrons secreted?
Reassembled lipids and APO-lipoprotein
Into lymph
What color will stool be when there is insufficient Bile? Where there is insufficient pancreatic enzymes?
Light/clay colored
Normal
What two enzymes does Orlistat inhibit? What does this cause? Side effects are similar to what disorder?
Inhibits gastric and pancreatic lipase
Reduces fat absorption
Steatorrhea
What is Olestra? How does it interact with lipase? What supplement must be given?
Fatty acyl resistant to lipase (taste and consistency of fat)
Supplement fat soluble vitamens
What does Ezetimibe inhibit? What does this decrease?
Inhibits NPC1L1
Deccreases cholesterol absorption
