Lecture 23: Metabolism of Fatty Acids Flashcards
Which of the following statements is INCORRECT about fatty acids?
-Saturated fatty acids have higher melting temperature than unsaturated fatty
acids.
-Naturally occurring unsaturated fatty acids mostly have double bonds in trans
configuration.
-ω-3 and ω-6 fatty acids are nutritionally essential fatty
-Polyunsaturated fatty acids such as arachidonic acid are used as precursors
to make eicosanoids
Excess energy is stored as
fat
Fatty acids are synthesized from
acetyl CoA
Liver and adipose tissue convert
glucose to fatty acids to triacylglycerol
Triacylglycerol
-leaves liver in VLDL lipoprotein
-enters blood
-stored in adipocytes
adipocytes
-store triacylglycerol
Brown fat cell
-many mitochondria producing heat with little fat particles scattered
Fatty acid synthesis
-cytosol
-acetyl CoA +2 Carbons at a time
-carried by ACP or FA synthase through THIOester bond
-2 NADPH used per cycle
-carboxyl group of malonyl CoA released as CO2
-final product released from ACP by hydrolysis
Transfer of acetyl CoA
-acetyl CoA from mitochondria cant cross membrane
-transported to cytosol as citrate
Malonyl CoA
-substrate for FA synthesis
-inhibits FA oxidation
Commitment step of FA synthesis
-acetyl CoA to Malonyl CoA by acetyl-CoA carboxylase
-use ATP
Acetyl CoA carboxylase regulation
-Activated by citrate and isocitrate
_INHIBTED by acyl CoAs
Acyl carrier protien (ACP)
-carries growing fatty acid chain thru thioester bond (covalent)
-releases final product by hydrolysis
Modification of Fatty Acids
-palmitate can be elongated
-adding double bonds with desaturases
palmitate
-humans synthesize as saturate C16 acid
-elongated by enzymes other than FA synthase (stearate = C18)
Desaturases
-add double bonds to FA
-only up to the 9th carbon
-3,4,5 positions only act on FAs with doublle bond at 9th carbon
-omega 3 and omega 6
essential fatty acids
-omega3
-omega6
Hydrolysis of Triacylglycerol
-lipases
-triacylglycerol to glycerol and 3 FAs
-glycerol converted for either glyolysis or gluconeogenesis
-FAs used for energy production through OXIDATION
Acyl CoA
-activate fatty acids
-used for oxidation or synthesis
-needs to be converted to acylcarnitine to get into mitochondria for oxidation (rate-limiting step)
Acylcarnitine
-converted form of acyl CoA that can be transported into mitochondria from cytosol for FA oxidation
-RATE-LIMITING step of FA oxidation!
RATE-LIMITING step of FA oxidation
transportation of acyl CoA to mitochondria as acylcarnitine
Carnitine palmitoyltransferase (CPT I)
-INHIBITED by malonyl CoA
B-oxidation
-2 Cs removed from acyl CoA as acetyl CoA at a time
-Produces NADH, FADH2, and Acetyl CoA
-go on to fuel TCA, substrate for ketone bodies and cholesterol
Propionyl CoA (C3)
-FAs with odd number of carbons after B-oxidation
-can be converted to Succinyl CoA (ANAPLEROTIC)
Oxidation of palmitate to acetyl CoA produces (in ATP)
26 ATP
Synthesis of palmitate from acetyl CoA REQUIRES (in ATP)
49 ATP
Compartmentation (Fatty acids)
-oxidation in mitochondria
-synthesis in cytosol
-prevents futile cycle
