Lipolysis, FA Oxidation, Ketogenesis Flashcards
describe lipoysis within an adipocyte
3 sequential enzymes: adipose triglyercide lipase (ATGL), hormone sensitive lipase (HSL) which works on digylericde, and monoglyceride lipase (MGL) . ATGL and HSL are highly regulated and HSL uses perilipin for its action
what is lipoprotein lipase?
it is produced in adipocytes and then expressed on the surface of cells and acts on the circulating TGs to convert them into FAs for uptake
what is pancreatic lipase?
this is responsible for hydrolysis of ingested TGs in the small intestine
what are free fatty acids?
FFAs are circulating in plasma or bound to albumin and are available as oxidative fuel
where does fatty acid oxidation take place?
in the mitochondria of all cells except the brain and RBCs
what protein is responsible for FA uptake in cells?
CD36
what happens to FAs after cellular uptake?
fatty acyl-CoA synthases catalyze fatty acyl-CoA. This cannot pass through the mitochondrial matrix, so it is converted via carnitine acyltransferase 1 (CAT-1) to fatty acyl carnitine, which can enter the mitochondria
what is CAT-1?
this is an enzyme that converts fatty acyl-CoA into fatty-acl carnitine for passage into the mitochondria, this is allosterically inhibited by malonyl-CoA which is high when glucose is present
what is CAT-II?
this reforms fatty acyl-CoA from fatty acyl-carnitine
what is beta oxidation in the mitochondria?
beta oxidation occurs initially at the beta carbon and goes through several cycles of releasing 2 carbons through acetyl CoA, each cycle produces 1 FADH2 and 1 NADH for the ETC. The acetyl-CoA can enter the TCA and make more ATP, but this requires replenishment to form OAA
describe the energy yield per mol of FA CoA
80 ATP from acteyl CoAs, 10.5 from FADH2, 17.5 from NADH, ATP utilization -2, total of 106 total ATP per mol
describe ketogenesis
this occurs only in the liver with low levels of OAA (from low levels of glucose), when the acetyl-CoA is shuttled into an alternative pathway this forms acetoacetate and B-hydroxybutyrate which are the ketone bodies
where does ketone oxiation occur?
the brain and muscle
how are ketones taken up into the body?
monocarboxylate transporter MT/MTT
how does the energy yield of ketones compare to glucose?
more energy yielded and less oxygen is required
