Biochem lec 3 - Lipid Metabolism - Metabolism of dietary lipids Flashcards
characteristics of lipids
heterogenous group of water insoluable (hydrpophobic) organic molecules
major source of energy
where does digestion of lipids begin and what is it catalyzed by
begins in stomach
catalyzed by lipase (an acid stable enzyme)
triacylglycerols (TAGS) are the primary targets
where does emulsification of dietary lipids (fats) occur?
small intestine (duodenum)
increases the surface area of the hydrophobic lipid droplets so that digestive enzymes can act effectively
fats are carried out of the small intestine by what
bile salts (hydrophillic points out, hydrophobic will interact w fat)
which pancreatic enzyme degrades TAG
pancreatic lipase
which pancreatic enzyme degrades cholesterol esters
cholesterol esterase
(cholesterol esters to cholesterol and free FAs)
which pancreatic enzyme degrades phospholipids
phospholipase A2 and lysophospholipase
where does degradtion of dietary lipids occur
in the pancrease by pancreatic enzymes
what is too large to be taken up efficiently by the mucosal cells of the intestinal villi
triacylgercol, therefore acted upon by pnancreatic lipase
most dietary cholesterol is present in what form
free form (nonesterified)
what does phospholipase A2 do
removes 1 FA from C2 leaving a lysophospholipid
what does lysophospholipase do
remove the FA at C1 leaving a glycerophosphoryl base
how does cholecystokinin have hormonal control of lipid digestion in the small intestine
stimulates the release of bile and pancreatic enzymes
how does secretin have hormonal control of lipid digestion in the small intestine
secretin stimulates bicarbonoate and water
(helps w synthesis of fatty acids)
what do lipids along w bile salts and fat soluble vitamins form
mixed micelles
(disk shaped clusters of amphipathic lipids that coalesce with their hydrophobic groups on the inside and their hydrophilic groups on the outside
what is the primary site of lipid absorption is where of the enterocytes
brush border membrane
another name for intestinal mucosal cells
enterocytes
the mixture of lipids absorbed by the enterocytes are synthesized to complex lipids in what location?
(resynthesis of TAG and cholesteryl esters occurs where)
in the ER
lipid malabsorption can result in what
steatorrhea (lipid in the feces)
what is lipid malabsoprtion/steatorrhea caused by?
disturbances in lipid digestion/absorption
newly resyntheiszed TAGS and cholesterly esters are very hydrophobic or hydrophilic, and therefore aggregate in what type of environments
very hdrophobic, aqueous environments
lipid droplets (chylomicrons) are surrounded by
and this increases or decreases the solubility of the droplet particle
-phospholipids
-unesterified cholesterol
-apolipoprotein
increases the solubility
chylomicrons are released by what from what into the lacteals
exocytosis from enterocytes
what are lacteals
lacteals are lymphatic vessels originating in the villi of the small intestine
chylomicrons follow the lympatic sytem then enter what
the blood
after chylomicrons enter lymph, ___
they enter the blood
TAGs are drawn off by muscle and fat cells
then chylomicrons remnants are removed from the blood by the liver
TAGs contained in chylomicrons are broekn down primarily where
in capillary beds of skeletal muscle and adipose tissue
lipoprotein lipase
break down TAG, attach to the line surface in blood vessels/capillaries so it can be taken by cells
(degrades circulating triglycerides in the bloodstream)
Hormone sensitive lipase -
breaks down TAG to drain storage (regulates lipid stores in adipocytes and steroidogenic tissues)
fatty acids
-directly taken up by muscle cells and adipocytes
-travel in blood until taken up by cells
-produce energy in some cells
-stored as TAGs in some cells
glycerol used almost exclusively by what to do what
by liver to produced glycerol-3-phosphate which can enter glycolysis or gluconeogenesis by oxidation to DHAP
remaining chylomicron components taken up by what
by liver and hydrolyzed to their component parts
some can be recycled by the body
