Lipids and Lipoproteins Flashcards
Major storage form of fatty acids are:
Triacylglycerols
Sources of Triacylglycerol
Dietary and de Novo (liver hepatocytes and adipocytes)
Progression of TG synthesis in Intestinal Cells
Dietary triacylglycerols → FA’s → Fatty acyl CoA → Diacylglycerol (DAG) → Triacylglycerol (TG) + apolipoproteins + other lipids → Chylomicron
What enzyme converts fatty acids to fatty acyl CoA?
fatty acyl CoA synthetase
Progression of TG synthesis from glucose in Hepatocytes
Glucose (via glycolysis) → DHAP + NADH → Glycerol-3-P
What enzyme is specific to TG synthesis in hepatocytes?
Glycerol kinase
Progression of TG synthesis from glycerol in Hepatocytes
Glycerol (free floating) + ATP + Glycerol kinase → Glycerol-3-P
Progression of TG synthesis de novo in Hepatocytes
Acetyl CoA (via de novo fatty acid synthesis) → fatty acid (enzyme fatty acyl CoA synthetase uses ATP to add CoA)→Triacylglyerol + apolipoproteins + other lipids→VLDL
VLDL stands for:
Very Low Density Lipolipids
What glucose membrane transporter imports glucose into adipocytes?
GLUT4
Chylomicron and VLDL + ?? lipase produces fatty acid
capillary lipoprotein lipase
Progression of TG synthesis from chylomicrons and VLDL in adipocytes
Via action of enzyme capillary lipoprotein lipase: Chylomicrons + VLDL (from intestinal and liver pathways) → fatty acid → Triacylglycerol (stored here in adipocytes)
Capillary lipoprotein lipase is stimulated by what hormone?
Insulin
DHAP (from glycolysis) becomes Glycerol 3-Phosphate via what adipocyte based dehydrogenase?
Glycerol 3-phosphate dehydrogenase
Breakdown of triacylglycerol occurs in
adipocytes
Promoters of triacylglycerol breakdown:
glucagon, epinephrine, norepinephrine
Inhibitor of triacylglycerol breakdown:
insulin
Which enzyme releases one fatty acid from triacylglycerol?
Hormone - sensitive lipase
Which enzyme releases one fatty acid from diacylglycerol?
Lipoprotein lipase
Which enzyme releases one fatty acid from monoacylglycerol?
Monoacyl-glycerol lipase
What is the product molecule following removal of all three fatty acids?
Glycerol
Short chain fatty acids are released into what? Where do they go?
Into blood stream and then the liver
Longer-chain fatty acids are bound to what and go where?
They are bound to albumin and go to the liver
Hormone-sensitive lipase (HSL) is activated via phosphorylation by what kinase?
PKA
PKA is activated by what?
Glucagon and epinephrine via cAMP and a GPCR signaling cascade
Hormone-sensitive lipase (HSL) is inactivated via dephosphorylation by what phosphatase?
Protein phosphatase 1 (PP1)
Protein phosphatase 1 is activated by what hormone?
Insulin
What is perilipin and why does anyone care?
Perilipin is a family of proteins that coat lipid droplets in adipocytes and muscle cells. They are a target of obesity treatment.
What do perilipins do?
They regulate lipolysis by controlling physical access of hormone-sensitive lipase to the fatty acids
The phosphorylation of perilipin allows what?
Phosphorylation allows Hormone-sensitive lipase access to fatty acids. Promotes lipolysis.
What phosphorylates perilipin?
PKA!