25 terms

Digestion and transport of dietary lipids

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Terms in this set (...)

American diet intake of fat
Less than 30%
recommended intake of fat
Lingual and gastric lipases
back of tongue digests short& medium chains, less than 12C (active in infants for cow's milk)
a gut hormone that stimulates the secretion of pancreatic enzymes
Bile salt
binds to globules of dietary fat made my peristalsis to increase the surface area, come from cholesterol, lack doubt bond and has more -OH which means that its more soluble
Bile salt fate
5% leave via feces 95%reabsorbed at ileum, go to liver then are stored in the gallbladder
Pancreatic lipase
digests dietary TAG, works on FA of all lengths from position 1 & 3 (secreted with co lipase and bicarb-stimulated by secretin to raise pH to 6)
remove FA's from compounds an example is cholesterol esterase
Phospholipase A2
digests phospholipids making a free FA and a lysophospholipid
tiny microdrolets emulsified by bile salts after digestion, they travel through a layer of water to the microvilli where lipids are absorbed and bile salts are left behind
Short and medium chains of FA
don't need bile salts for absorption, go into blood bound to albumin and not lymph
Synthesis of TAG
in the epithelial cells, FAs are activated to fatty acyl CoA+ 2-monoacylgrylcerol diacylglycerol reacts with fatty acyl CoA then TAG
intermediate of TAG synthesis in intestinal cells
Phosphatidic acid
intermediate of TAG synthesis in tissues that is not intestinal cells
Synthesis of chylomicrons
- phospholipids come with other proteins and contain cholesterol, fat soluble vitamins, and apoproteins
RNA editing
a gene makes Apo-B in mRNA the "C" is switched to "U" which results in a stop codon so result is not ApoB-100 (for VLDL) but ApoB-48 for Chylomicrons
How are chylomicrons released?
Exocytosis into the chyle of the lymphatic system then enter blood via the thoracic duct
How long does it take for chylomicrons (dietary fat) to enter blood?
1-2 hours after the start of meal and continues for many hours
Nascent chylomicrons
accept proteins from HDL in the lymph and blood result in a mature chylomicron
transport apoE and apoCII
recognized by the receptors in the liver and enter by endycytosis and then is digested by lysosomes
activates LPL (lipoprotein lipase) which is on the capillaries endothelial cells (proteoglycans in the basement membrane) of muscle and adipocytes and cells of lactating mammary glands
LPL isozyme in adipose tissue
has a high Km then muscle (think heart) because you only want it to be most active after a meal when TAG is abundant
LPL (lipoprotein lipase)
digest TAG of the chylomicrons and VLDL
an artificial fat substitute, taste without calories it's a sucrose molecule with FA that are esterifies, can't be hydrolyzed by the pancreatic lipase and pass through the intestinal tract