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INTRODUCTION
• Molecules that contain hydrocarbon • Make up the building blocks of the structure
and function of living cell• Hydrophobic
DIGESTION
• StomachLingual lipase(2.5-5)
Active in stomach, from mouthActs on short chain triglycerides(SCT) eg milk,ghee and
butterMore significant in newborn infants
Gastric lipase(5.4)Acid stableSecreted by chief cellStimulated by gastrin
30% digestion
• IntestinesBile(7.7) neutralize acid chymeEmulsification by bile salt
Lipids disperse into smaller dropletsReduce surface tensionSurface area increasedFavoured by bile salt, peristalsis and phospholipid
Pancreatic lipaseHydrolyse fatty acid (1st and 3rd )Isomerase shift ester bond (2nd to 1st), then hydrolyse2-Monoacycl glycerol(78%), 1-Monoacyl glycerol
(6%),glycerol and fatty acids(14%)Partial ( incomplete)
Cholesterol EsteraseCholesterol ester hydrolysed to free cholesterol and
fatty acidsPhospholipase A2
Produces lysophospholipid and a fatty acidC0- lipase
Secreted by pancreas as inactive zymogenActivated by trypsinNeeded for lipase reaction
ABSORPTION
• Short Chain Fatty Acid and Medium Chain Fatty AcidNot need re-esterificationDirectly enter blood vessel, through portal vein
to liverRapid absorption
• Long Chain Fatty Acid
Absorb by mixed micelle formation from intestinal lumen to the mucosal cell of intestine.
What is micelle?Physical aggregates of bile salt and phospholipid that carry digested lipids and fat soluble vitamins to mucosal cell of intestine.
Where it is located?microvillous surface of jejunal mucosa
LCFA re-esterified to form triglyceride inside interstinal mucosal cell
Free glycerol absorbed from the intestinal lumen directly enters into bloodstream.
The bile salts are reabsorb from the large intestine and returned to liver via enterohepatic circulation.
The chylomicrons are used for transport of lipid from the intestinal mucosal cells trough lacteal into thoracic duct and empties lymph circulation. cylomicrons
Lipid partTAG
phospholipid
Cholesterol ester
Protein partApo-B-48Apo-A (intestinal cell)
Apo-EApo-CII (from HDL)
DISORDER
AbnormalitiesDefective digestion
(unsplit fat) chronic
pancreatic disease
steatorrhea
Defective absorption (split fat)
Celiac disease,
sprueCrohn’s
disease
Surgical removal of intestine
Obstruction of bile
duct
Chyluria
chlylothorax
CONCLUSIONLipid digestion involve 3 enzyme at 3 different location: Ligual lipase-stomach Gastric lipase-stomach Pancreatic lipase-small intestine
Lipid absorption: Minor digestion Major digestion Bile acid facilitated formation of micelle Passive absorption Reesterification Chylomicron formation