Flashcards in 129b Lipid Digestion Deck (14)
major component of dietary lipids
90% triglycerides (TG's) - 3 fatty acids attached to glyceride via ester bonds
+ cholesterol esters, PL, Vit ADEK
what happens to fat that is consumed?
Almost all is absorbed - stored in adipose tissue
most takes places in small intestine (minor in mouth and stomach via acid stable lipases)
what is the basic process involved in fat absorption/digestin? what are the primary products that are transported into enterocytes?
hydrolysis through a variety of enzymes
digestion in small intestine
1) pancreas releases...
Lipase/colipase: TAG --> MAG + 2FFA
Cholesterol esterase: CE --> chol + ester
phospholipase A2: PL-->FA + lysoPL
2) Liver releases bile to soluble products in mixed micelles
what does liver bile do?
solubilizes the lipid breakdown products (MAG, GGA, cholestrol) in mixed micelles
after absorption, how do fats leave intestine?
chylomicrons via lymphatics
after reesterification of 2MG, lecithin, cholestrol with FFA to form TG/chol ester/PL
how are TG absorped?
not by self - ester bonds must be broken to form
MG and 2 FFA
what are bile acids made from?
critical micelle concentration
concentration at which molecules self-associate to form micelles (1-2 mM for mixed bile salts)
how are fats absorped in liver cells?
MG and FFA -- passive diffusion across lipid bilayer
what happens in liver cell?
remade into TG via MGT and DGT
packaged with chylomicrons and exocytosed into lymphatics (lacteals)
some FFA can be absorbed into portal blood (short and medium length (
95% of bile acids are reabsorbed via ABST (apical Na dependent bile salt transporter b/c polar) in terminal illelium if not deconjugated
passive absorption (when small intestine bacteria deconguate bile salts to form bile acids)
pancreas secretes lipase
sphincter of Oddi relaxes
contracts the gall bladder