Triglyceride, Phospholipid, and Sphingolipid Metabolism Flashcards
Where does phosphatidylethanolamine synthesis begin?
The cytoplasm
How does short term fatty acid metabolic regulation work? What mechanisms?
Allosteric regulation, covalent modification of AMPK (AMP kinase), and hormones
How does long term fatty acid metabolic regulation work? What mechanisms?
Changes in gene expression
Which regulatory hormones phosphorylate protein kinases? Which hormones dephosphorylate?
Glucagon/epinephrine phosphorylate
Insulin dephosphorylates
What are the allosteric modulators of FA metabolism?
NADH, thiolase, malonyl-CoA, long chain fatty acids
What inhibits beta-hydroxyacyl-CoA-dehydrogenase? When does this reaction occur?
NADH
Third reaction in beta-oxidation
What inhibits thiolase? When does this reaction occur?
Acetyl Co-A
Fourth step in beta-oxidation
What inhibits CAT-I? What hormones affect this? What is CAT-I?
Malonyl-CoA (ACC product)
CAT-I = Carnitine-Acyl Transferase
High insulin/glucagon ratio leads to high malonyl-CoA level that causes the inhibition of beta-oxidation in liver
What inhibits ACC? What is ACC?
ACC = Acetyl-CoA Carboxylase
High long chain fatty acid acyl-CoA level inhibits ACC (depolymerization) -> blocks FA synthesis
What activates AMP-activated protein kinase (AMPK)?
High AMP/ATP ratio
When does AMP level increase?
In response to stress, nutrient deprivation, and prolonged exercise
What does AMP do?
Promote phosphorylation reactions and inhibit dephosphorylation
What does AMPK do?
Switches off anabolic pathways and switches on catabolic pathways
Inhibits FA synthesis by inhibiting ACC (phosphorylation)
Inhibits TG synthesis by inhibiting glycerol-3-phosphate-acetyltransferase
How does insulin regulation of FA metabolism work?
Insulin- promotes fat synthesis by signal transduction; activates ACC by dephosphorylation; triggers GLUT4 to cell surface
How does epinephrine/glucagon regulation of FA metabolism work?
Increases lipolysis by stimulating phosphorylation
How does long term regulation of FA metabolism work (w/transcription factors)
Insulin upregulates genes that code for enzymes in FA and NADH synthesis
Glucagon and Long-chain FAs inhibit this
What are the two classes of transcription factors involved in FA metabolism?
SERBPs and PPARs
What are lipoproteins?
Group of molecular complexes found in the blood plasma of mammals
Transport lipid molecules through the bloodstream from organ to organ
Where are protein components for lipoproteins synthesized? What are they called
Apolipoproteins
Synthesized in liver (VLDL) or intestine (chylomicrons)
What is the endogenous lipid transport pathway?
Transport of recently synthesized TG packaged in VLDL from liver to other tissues?
What is the exogenous pathway?
Transport of recently synthesized TG packaged in chylomicrons to other tissues
How are lipoproteins classified?
According to their density
low density = more triacylglycerols
high density = more proteins
What are the classes of lipoproteins? What do they do?
Chylomicrons- transport dietary TG and cholesterol to muscle and adipose tissues
Very-low-density lipoproteins
Intermediate-density lipoproteins (same as VLDL, but once they have delivered their triacylglycerol molecules)- transport lipids to tissues
Low-density lipoproteins- transport cholesterol and cholesterol esters to tissues
High-density lipoproteins- scavenge cholesterol and cholesterol esters from VLDL and LDL, and transport to liver and steroid synthesizing organs
What are the apolipoproteins that correspond to each lipoprotein? What do they do?
Nascent chylomicron- B48
Mature chylomicrons- B48, C-II, E (latter two acquired from HDL) - activates lipoprotein lipase (LPL)
Chylomicron remnants- B48, C-II, E (latter 2 from HDL) - binds liver specific receptor for removal from blood
Nascent VLDL- B100
Mature VLDL - B-100, C-II, E (latter 2 from HDL) - activates LPL
ILDL - B-100, C-II, E (latter 2 from HDL) - binds liver specific enzymes for removal from blood
LDL - B-100, C-II, E (latter 2 from HDL) - binds to LDL receptor to deliver cholesterol
