Dietary Lipids

Question 1

Hormonal control of digestion

Answer 1

Intake meal - mucosa of jej and duod produce CCK - CCK causes gall bladder to expel bile and panc enzyme - slows gastric contractions - secretion from mucosa responds to low pH chyme and induces panc bicarb to neut - optimal pH. Process increases insulin

Question 2

Lipases

Answer 2

Enzyme of lipid digestion. first in stomach = acid stable lingual lipase. Primary target = short and medium chain FA TAGs (milk)

Question 3

Emulsification of lipids

Answer 3

with aid of bile salts in duod, increase micelle SA
Bile salts (glyco and taurocholate) create stable particles; enzymes adhere to micelles and graze 1 FA at a time

Question 4

Degrade of TAGs

Answer 4

Too large for mucosal uptake

Pancreatic lipase cleaves ester bonds at each end to create 2 FFAs and monoglycerol

Colipase holds panc lipase at interface between lipid and aqueous media and allows exposure of lipase to active site. Activate by chymotrypsin (zymogen). Inhib via Orlistat

Question 5

Panc neut pH lipid hydrolases in intestine

Answer 5

Cholesterol Esterase - removes ester

PLA2 - after PL’s action at C2, remaining Fatty Acyl removed via lysophospholipase leaving soluble glycerophosphate

Question 6

Lipids enter at brush border

Answer 6

Short and Med chain enter without Micelle aid, abs mostly as monoglycerides and FFAs, reassembled into TAG in mucosa. TAG, chol, PL to CM. CM exit mucosa and enter lymph to circulation via thoracic duct

Question 7

Fate of LCFA and chol in mucosa

Answer 7

Upon absorb - LCFA and chol are esterfied. First act to FA-CoA by FA-CoA synthase (thiokinase) with 2 ATP

Question 8

Fate of SC and MC FA

Answer 8

not esterfied: enter portal circulation directly with albumin to liver

Question 9

mucosal cells and CM

Answer 9

Assemble and secrete CM with ApoB100

Question 10

CMs

Answer 10

Sole LP carrier of dietary lipid
In liver - gene transC into ApoB100
In intestine - same gene ApoB100 to ApoB48; mod via transC processing

Question 11

CM assembly

Answer 11

ApoB48 with lipid requires MTP (ER) = microsomal Triglyceride transfer protein

Question 12

CM role

Answer 12

Accelerates transport of TAG, chol esters, and PLs across organelle membrane. As ApoB48 made - lipid begins to associate with it in a process catalyzed by MTP

Question 13

MTP def

Answer 13

Beta lipoproteinemia - deficient assembly of all ApoB bearing lipoproteins (CM, VLDL, IDL, LDL)

Question 14

CMs function

Answer 14

Exocytosed into lacteals of gut. Roles = Seperate fats from water and signal cells, cargo of lipid

Question 15

HDL and CM

Answer 15

Key apoproteins are acquired from HDL that function as roving resevoir of ApoProteins
ApoC 2 - activates LPL
ApoE: hepatic endocytosis of CM

Question 16

CM empty

Answer 16

emptied by membrane LPL and glycerol to liver. LPL held by GPI with Hep Sulfate (SO4 bound). Fat does not go to Liver and Brain via CM

Question 17

LPL variants

Answer 17

Cardiac and Skl M 1/15th of rest to indicate constant need

Question 18

Defects in lipid absorb

Answer 18

Leads to steatorrhea, def in FAs and fat soluble vits (ADEK) leading to blood clot disorders and dermatitis and others