Lipid Metabolism Flashcards
What are the dietary lipids?
-triacylglycerols (TAGS)
-fat soluble vitamins (FSVs)
-cholesterol and cholesteryl esters (CEs)
-phospholipids (PLs)
TAG digestion in the stomach
using gastric lipase:
breaks down some TAGS into DAGS (diacylglycerol) + fatty acids (FAs)
TAG digestion in the small intestine (short story)
-bile creates emulsification droplets
-pancreatic colipase and lipase
TAG digestion in the small intestine (long story)
-cholecystokinin is secreted by the duodenum
-acts on pancreas to secrete digestive enzymes pancreatic pancreatic lipase & colipase
-acts on gallbladder to secrete bile
-bile breaks up fat gobules into small emulsification droplets
-colipase allows lipase to enter emulsification droplets
-lipase breaksdown TAGS & DAGs into MAGS (monoacylglycerol) and free fatty acids
What are the products of digestion?
MAGS and FAs
Lipid absorption
mixed bile salt micelles transport lipids to brush border for absorption
Emulsification droplets become what once digestion is complete?
mixed bile salt micelles
Absorption of MAGs + FAs occurs via
transporters at the brush border
What do products of digestion go?
the endoplasmic reticulum
What carries MAGs + FAs to the endoplasmic reticulum
transport proteins
What transport protein specifically carries the products of digestion to the ER?
via fatty acid binding protein (FABP)
What happens in the ER?
MAGs + FAs turn into TAGs
What happens in the ER after the reesterification of TAGs
the TAGs are then packaged into chylomicrons and enter the lymph for transport to the heart
What happens during ruminant lipid digestion
-TAGs turn into glycerol + FAs
-biohydrogenation of PUFAs
What is the process of lipid digestive in a ruminant?
-microbes breakdown TAGs into glycerol + FAs and the glycerol is converted to UFAs which are absorbed through the rumen wall
-FAs from plant material are polyunsaturated fattyacids (PUFAs)
-microbes bihydrogenate PUFAs into saturated fatty acids (SFAs)
-SFAs continue on through the digestive tract for absorption in the S.I.
What are the various lipoproteins?
-chylomicrons
-very low density lipoproteins (VLDL)
-low density lipoproteins (LDL)
-high density lipoproteins (HDL)
Whats apolipoprotein?
protein associated with lipoproteins
that is used for:
-structural
-enzyme cofactors
-ligands for receptors
What do chylomicrons have?
Apo B48
Where do Chylomicrons enter? from?
enter the lymph from the s.i. for transport to the heart
What happens with chylomicrons after they enter the lymph?
-when enters the bloodstream, chylomicron will associate w/ Apo C-2
-chylomicron travel through the bloodstream and when the Apo C-2 binds to lipoprotein lipase on capillary wall, TAGS in chylomicron is broken down into glycerol + FAs
-once 80% of TAG have been released, the chylomicron dissociates from Apo C-2 & become chylomicron remnant
Where do FAs go?
they enter the cell and are used for energy
Where does glycerol go?
goes to the liver
How is chylomicron remnant removed from bloodstream?
via apo B48 receptor on liver
What do VLDLs have?
Apo 100 and Apo E
Where do VLDLs go? from?
released into bloodstream from liver
What happens with VLDL when released into the bloodstream?
- when enters bloodstream, VLDL will associate w/ Apo C-2
-VLDL travel through the bloodstream and when the Apo C-2 binds to lipoprotein lipase on capillary wall, TAGS in VLDL is broken down into glycerol + FAs
-when over 1/2 of TAG is released by VLDL, Apo C-2 dissociates & VLDL becomes IDL
-when over 80% of TAG has been removed apo E dissociates & IDL becomes LDL
How is TAG removed from IDL?
apo E binding to receptors on capillary walls
What do LDLs have?
Apo B100
What happens with LDL?
when apo B100 binds to receptors on capillary walls, cholesterol diffuses out of the LDL into tissue
How are LDLs removed?
LDLs are removed from circulation by Apo B100 receptors on liver
What do HDLs have?
Apo A-1
What are HDLs secreted by?
HDLS
What do HDLs do?
perform reverse cholesterol transport
-when Apo A-1 binds to receptors on capillary walls, cholesterol is removed from tissues and diffuses into HDL
What removes HDL from circulation?
liver removes via apo A-1 receptor
What are the biological roles for lipids?
-energy source
-structural components of membranes
-lubricants
-signaling molecules
Fatty acid synthesis
-liver and adipose tissue
-lactating mammary gland
