3.3 Lipid Catabolism Flashcards
fatty acid release def
the cytosolic breakdown of triglycerides (highly nonpolar so most of energy is stored in these fats) during starvation of glucose and glycogen by using lipase(responsible for cleaving ester bonds so that small intestine can absorb the substituents of the monoglycerol and fatty acids) through lipolysis
fatty acid transport
- occurs in the cytosol
- covalently bonded to coenzyme A to make acetyl co A to activate it
- has a carnitine shuttle (moves from cytosol to mitochondrial matrix)
what is coenzyme used for?
- biosynthesis of fatty acids
- oxidation of fatty acids
- oxidation of pyruvate
define lypolysis
lipase will break the parent triglycerides and will become desterfied/hydrolysed to get rid of ester bonds so that the new tryglycerides can be used to generate high energy when moved to the matrix of mitochondria BUT HAS NOT YET TRANSPORTED TO THE MATRIX DURING LYPOLYSIS
what is the main purpose of the carnitine shuttle?
to take the newly formed tryglyceride from lipolysis from the cytosol to the matrix
-it also gives access to beta oxidation
what is beta oxidation?
produces reduced cofactors FADH2 and NADH and acetyl coA
what carbon number is beta on a fatty acid?
3
appearance factors of coA
- HS thiol group
- at least one phosphate group
- adenine
what does brackets mean on fatty acids?
the number of repeated units
fatty acid with 12 carbons and no double bonds?
protonated: lauric acid
ionized/ natural form: laurate
acyl group: lauryl
fatty acid with 14carbons and no double bonds?
protonated: mryristic acid
ionized/ natural form: myristate
acyl group: miristyl
fatty acid with 16 carbons and no double bonds?
protonated: palmitic acid
ionized/ natural form: paulmitate
acyl group: paulmyl
fatty acid with 18 carbons and no double bonds?
protonated: stearic acid
ionized/ natural form: stearate
acyl group: stearyl
triglycerol appearance
three carbonyl , three CH, three r groups and fatty acid part is carbonyl
acetyl coA synthetase
acetyl group of fatty acid wants the phosphate group f atp and
when binded the thiol of S co A will do nucleophilic attack on carbon of mixe anhydride atp fatty acid
makes thiol
carnitine acetyl transferase I
quaternary amine that will have acyl-CoA is first converted to acyl-carnitine by carnitine acyltransferase I—an enzyme located at the outer (intermembraneous space) surface of IMM—in order to exploit the carnitine shuttle system for its delivery into the mitochondrial matrix
carnitine-acylcarnitine translocase
Acyl-carnitine is shuttled across the inner mitochondrial membrane (IMM)—from the cytosol (or the intermembraneous space) to the mitochondrial matrix
carnitine acetyl transferase II
catalyzes the reverse transfer of acyl group of acyl-carnitine back to CoA to generate acylCoA and free carnitine
what happens to the free carnitine
goes back to cytosol to be recycled
acyl vs enoyl
acyl has 1 double bond bc of acetyl
enoyl will have 2 double bond
acyl-CoA dehydrogenase
Dehydrogenation of saturated C-C single bond within acyl-CoA results in the formation of enoylCoA harboring a C=C double bond and requires strong FAD to make double bond of high energy
hydration
Hydration of unsaturated C=C double bond within trans-2-enoylCoA (prochiral) results in the formation of L-beta-hydroxyacyl-CoA
beta -Hydroxyacyl-CoA Dehydrogenase
usually involving keta it is NAD which reduces
Oxidation of –OH to a keto group at the C position within L-beta-hydroxyacyl-CoA results in the formation of corresponding ketoacyl-CoA
beta Ketoacyl-CoA Thiolase
Thiolysis (or breaking bonds with –SH group—cf hydrolysis and phosphorolysis) initiated by nucleophilic attack of the thiol group (-SH) of CoA on the keto group within -ketoacyl-CoA results in the cleavage of C-C bond, thereby releasing the first acetyl-CoA
