Lipid Digestion and Absorption Flashcards
How many grams of lipids do adults consume?
- about 81g
- 90% TAG
- 10%
- cholesterol
- cholesterol esters
- phospholipids
- free fatty acids
Acid Lipase
acid-stable lipases function in the stomach at optimal pH between pH 4 and 6
- want to break ester bonds
- lingual lipase
- gastric lipase
- target TAG containing short and medium chain FA (milk fat)
- important in neonates
lingual lipases
- acid lipase
- secreted rom glands at back of tongue
- wants to break ester bonds
gastric lipase
- acid lipase
- secreted from the gastric mucosa
- wants to break ester bonds
emulsification of lipids
-small intestine
two complimentary actions:
- mechanical agitation
- bile salts secretion
mechanical agitation in emulsification of lipids
-dietary material via peristalsis increases the lipid droplet surface area
Bile salts secretion in emulsification of lipids
- made in liver
- stored in gallbladder
- secreted into small intestine
- detergent properties
detergent properties of bile salts
stabilize particles as they become smaller, prevents them from coalescing
components of bile
glycine and colic acid
pancreatic enzymes
secreted from the pancreas digest dietary TAG, cholesterol esters and phospholipids
digestion
the removal of specific FA by breaking ester bonds attaching the FA
What are some pancreatic enzymes?
- pancreatic lipase
- colipase
- cholesterol esterase
- phospholipase A2
- lysophospholipase
pancreatic enzymes responsible for TAG digestive
- pancreatic lipase
- colipase
pancreatic enzymes responsible for cholesterol ester digestion
-cholesterol esterase
pancreatic enzymes responsible for phospholipid digestions
- phospholipase A2
- lysophospholipase
TAG digestions
too big for intestinal mucosal cells to endocytose efficiently
pancreatic lipase
- pancreatic enzyme
- digestion of TAG
- cleaves FA of glycerol backbone
- produces 2 free FA
- 1 2-monoacylclycerol
- 2-3% total protein in pancreatic secretions
- VERY HIGH catalytic efficiency
colipase
- pancreatic enzyme
- TAG digestion
- binds pancreatic lipase at a 1:1 ratio
- promotes pancreatic lipase activity when inhibitory bile salts are present
cholesterol esteras
- pancreatic enzyme
- cholesteryl ester digestion
- 10-15% (esterified cholesterol)
- digests esterified cholesterol
Phospholipase A2
- pancreatic enzyme
- phospholipid digestion
- removes FA to produce lysophospholipid and a free fA
lysophospholipase
- pancreatic enzyme
- phospholipid digestion
Gut endocrine cells
sense: -lipids and partially digested proteins -the low pH of chyme entering the intestines Secrete: -CCK -secretin
CCK
-hormone secreted in response to presence of lipids and partially digested proteins
promotes:
- bile salts
- phospholipids
- free cholesterol
decreases:
- gastric motilitly
- reducing release of gastric contents
secretin
-hormone secreted in response to the low pH of chyme entering the intestine
promotes:
-bicarbonate, makes alkaline
micelles
- disk shaped clusters of amphipathic lipids
- formed from these three products, bile salts, and fat soluble vitamins (K,A,D,E)
Enterocytes
- coalese/arrange with hydrophobic groups burried and hydrophillic groups exposed
- micelles associate with the brush border of enterocytes
chylomicron
apolipoprotein B-48
- fat soluble vitamins inside here
- nonphospholipid bilayer
fatty acyl-CoA synthetase (thiokinase)
forms acyl-CoA
TAG synthase
makes TAG via acyltransferase activity
acyl CoA: cholesterol acyltransferase
-esterifies cholesterol with a FA
secretion of lipids from enterocytes
enterocytes—lymph system—vascular system
lipoprotein lipase
associates with the lumen of endothelial cells of capillary beds
-clip out FA from TAG in chylomicron
chylomicron digestion
liver takes up empty chylomictron and break down components to use for energy
lipid malabsorption in gallbladder/liver
bile issues, can’t stabilize droplets
lipid malabsorption in pancrease
enzyme issues (can’t clip lipids off of macromolecules)
lipid malabsorption in stomach
can’t bring stuff in
cystic fibrosis
- disability for producing pancreatic enzyme released into small intestine
- defect in chloride ion channel
- hard time getting water into ducts
- mucus clogs ducts
number one reason for lipid malabsorption
pancreatic
