BICH 411 ex 3 lipid metabolism

exogenous pathway

chylomicrons

endogenous pathway

LDL, VLDL, IDL, HDL

Fatty acids and monoglycerides are emulsified by

bile salts to form micelles that facilitate absorption in the intestines

FA’s enter the epithelial cells and link to form

Triglycerides

Triglycerides combine with proteins inside the _____ to form ____.

Golgi Body; chylomicrons

Chylomicrons enter the ____ and are transported away from ____

lacteal; the intestines

Major dietary lipids involved in digestion

triacylglycerols (cholesterol, free FAs, phospholipids, and cholesteryl esters)

Important enzymes involved in digestion

pancreatic lipases, colipases, and cholesterol esterases

protein digestion occurs in the

stomach

bile is made in the

liver and stored in the gallbladder.

intestine enzymes are made in the

pancreas

Emulsification

Micelles and solubilized fat globules produced by bile salts

interfacial activation

increase in activity when lipases interact with the surface of lipid droplets.

absorption involves the formation of

chylomicrons

FAs, mono-, and diacylglycerols must be absorbed by

mucosal cells in small intestines

only what type of monoglycerides and FAs can be absorbed?

freely dissolved

what aids in absorption by facilitating diffusion of lipids into mucosal cells

bile salts

what happens to FAs inside mucosal cells?

They are re-esterified into triacylglycerols.

chylomicrons are packaged:

TAGs, cholesterol esters, apoproteins, and vitamins

chylomicrons are transported via

the lymph system

bile salts mix with fats to form

mixed micelles

intestine lipases degrade TAGs to form

FAs and glycerols

FAs taken up by intestinal mucosa form

TAGs

reconstructed TAGs are packaged with cholesterol which are

chylomicrons

chylomicrons are shuttled through the lymph system and blood stream to the

tissues

chylomicrons are aided by what? and recognized by what?

aided by lipid binding proteins (apolipoproteins) and recognized by muscle/fat cell receptors on the surface

extracellular lipoprotein lipase is activated by

apoC-II in capillaries

after extracellular lipoprotein lipase is activated, FAs and glycerol are

taken up by the cells

FAs are used in what

muscle cells, then reesterfied into TAGs for storage in adipocytes

the major structural components of lipid transport

triacylglycerol, phospholipid, cholesterol, apoprotein

lipoproteins in order of density (lowest » highest)

chylomicrons « VLDL « LDL « IDL « HDL

chylomicrons

dietary TAGs, cholesterol, cholesteryl esters

VLDL

transport TAGs, and FAs from liver » tissue

LDL

major cholesterol carrier in blood stream

IDL

“transition particle” between TAG transport and cholesterol transport

HDL

used for cholesterol recovery and delivery to steroidogenic tissues

apoproteins

protein portion of lipoproteins, dictates interactions

apolipoprotein A1 (ApoA1) structure

homotetramer, wraps around HDL particle

ApoA1 binding occurs where

chylomicrons and HDL, adds a high degree of hydrophobicity

ApoA1 helps clear

fats and cholesterol from WBCs in arterial walls

Reverse cholesterol transport

ApoA1 facilitates interactions with SRb1 receptor within HDL liver

HDL binds to SRB1 and

transfers component lipids to the cell, depleted HDL dissociates from receptor

ABCG1

lipid homeostasis, tissue lipid levels and efflux (cholesterol » HDL)

ABCA1

cholesterol and phospholipids » ApoA1 (forms nascent HDL-nHDL)

LDL contains ApoB-100

in 1:1 ration

ApoB-100 structure

huge monomer that covers ½ of LDL

which apoprotein plays a role in LDL receptor mediated endocytosis

ApoB-100

LDL receptors are

transmembrane glycoproteins

LDL receptors target ApoB-100 in

clathrin coated pits

ApoB-100 and cholesteryl-esters hydrolyze to

amino acids, FAs, and cholesterol

ApoE structure

multiple isoforms that associate with chylomicrons and remnants

ApoE is found in

VLDL, IDL, and some HDL

ApoE has enhanced binding to

LDL receptors in the liver and CNS

defects in ApoE4 is correlated to

Alzheimer’s