UNIT 6: LIPIDS: Digestion and Function Flashcards
Where does lipid digestion begin?
Saliva
- lingual lipase
Triglycerides –> FFA and DG
no detergents present
What happens to lipids in the stomach?
- acid environment denatures proteins and muscle contraction promotes emulsification
- gastric lipase
- hydrolysis of TF sn-3 –> FFA and DA
What is the role of bile?
- bile secretes into duodenum, act as a detergent and facilitate micelle formation
How does fat enter the small intestine?
- as large lipid droplets
emulsified by mechanical shearing and detergent effects of bile
What is the role of pancreatic lipase
Pancreatic lipase
- hydrolyze TG at sn-2 and sn-3
What is the role of cholesterol esterase?
works with pancreatic lipase
- hydrolyze cholesterol-esters to release free cholesterol and FFA
What is the role of phospholipase?
release FFA and 2-lysophospholipid
Pancreatic lipase attacks what bonds?
ester bonds
- hydrolyze to release from TG
What happens right when 2lysoPL, MG, FFA, free cholesterol enter the inside of the enterocyte?
need to convert and reesterfy to form phospholipid, triglycerol, and cholesterol esters to prevent detergent actions
Once inside the enterocyte, where do the neutral/amphipathic lipids go?
to the golgi
What happens to the lipids in the golgi?
packaged as a chylomicron
What is bigger? Mixed micelles (prior to enterocyte) or chylomicrons (after packagingi n golgi)
Chylomicrons are much much bigger
Where do chylomicrons go after the enterocyte?
Leaves the intestinal cell and into the lacteal, enters the lymphatic system
–> destination: hepatocyte
What happens to chylomicrons prior to entering the hepatocyte?
- Apoproteins bind the chylomicron surface (Apo-C,-E,-B)
- lipoprotein lipase deplete TG core
What is the role of apoproteins?
- improve binding function to regulate metabolism further
- increase water solubility
How does lipoprotein lipase act on a chylomicron?
- LPL is bound to endothelial cell surface
- binds to ApoC
- deplete TG core - release FFA
- FFA taken up by cells that require more FFA (heart, skeletal)
What is a chylomicron remnant?
- a chylomicron depleted of TF
- shrink in size
- leftover is cholesterol esterase
How does the liver cell recognize the chylomicron remnant?
- liver receptor binds ApoE on chylomicron remnant
How are LPL anchored?
LPL are anchored to endothelial cells via a proteoglycan anchor
- LPL enzyme binds ApoC on chylomicron
ApoB, ApoC, ApoE bind to…?
all are bound to
- chylomicron
- VLDL
- LDL
