Lipid degradation

Question 1

Degradation enzymes in stomach

Answer 1

LINGUAL LIPASE, GASTRIC LIPASE

• degrade short- to medium chain lipids
• optimum pH 4-6
• orlistat inhibits the enzymes

Question 2

Degradation in duodenum

Answer 2

-emuslification: bile salts + peristalsis (increase surface area, makes smaller)
-pancreatic enzymes
induced by cholecystokinin CCK

Question 3

TAG’s

Answer 3

• degraded by pancreatic lipase

- colipase (activated by trypsin) anchors lipase to surface of lipids

Question 4

Cholesteryl esters

Answer 4

• hydrolysed by CHOLESTEROL ESTERASE= cholesterol + FFA

- enzyme activity increase by bile salts

Question 5

Phospholipids

Answer 5

• degrade by PLA2(activated by trypsin)
• cleaves one FFA, leaves lysphospholipid
• FFA removed by lysphospholipase

Question 6

Micelles

Answer 6

• FFA, cholesterol, 2-monoacylglycerol form with bile salts + fat-soluble vitamins
• micelles fuse with microvilli, enter enterocytes

Question 7

Fates of lipids after absorption

Answer 7

Whole mixture to ER

• TAG’s: resyntesized by TAG SYNTHASE
• Lysophospholipids: ACYLTRANSFERASES
• Cholesterol: esterified to FA by ACYL CoA CHOLESTEROL ACYLTRANSFERASE
• short+medium FA: portal circulation, carried by albumin

Question 8

Resynthesized particles

Answer 8

• packed as CHYLOMICRONS (phospholipids, cholesterol, apolipoprotein B48)
• released in lacteals
• lymph system to venous system