Biochem Lec 20-21 Flashcards
what is triacylglycerol
also known as triglyceride or TAG and the structure consist of a glycerol backbone attached to three fatty acid chains, also known as acyl chains, as this is where extra carbons are stored
these fat molecules are mainly stored in fat cells, muscle and other tissue
what does it mean to be saturated and how is that important in fats
fatty acyl chains are saturated, meaning they have no double bonds between the carbons, and that is important to allow close packing
the chains in TAG need ti be hydrolyzed off to be used
what is the overview on fat metabolism
the TAG stored in fat cells will be hydrolyzed, broken, into glycerol and fatty acids where the glycerol goes to liver cells and undergo gluconeogenesis to become glucose while the fatty acids chains go to also liver and other tissues to undergo fatty acid oxidation to become Acetyl CoA that get used in citric acid cycle
both end up generating energy
what will cause fatty acids to break and get transported from cell into other tissues to undergo beta oxidation
the hormones epinenphrine and glucagon which are active during fast state will cause intracellular signalling through GPCRs to activate lipase, the process of signalling involve the GPCR when stimulated will activated the adenylyl cyclase which converts ATP to cAMP and that will activate protein kinase A which will phosphorylate triacylglycerol lipase and phosphorylated lipase will hydrolyze ester bonds to produce the free fatty acids and glycerol by breaking triacylglycerol into diacylglycerol and then into monoacylglycerol and by other lipases that will lead to product of 1 glycerol and 3 fatty acid chains
which enzyme is the hormone sensitive lipase
triacylglyerol lipase is the hormone sensitive lipase
what transports the fatty acid chains after they have been freed
albumin will transport them in the blood
how are free fatty acids activated in cytoplasm
the acyl chains will get trapped in cell by covalent addition of coenzyme A and the acyl CoA synthase enzyme, a ligase that uses ATP, will form the fatty acyl CoA molecule and the pyrophosphate (PPi) get hydrolyzed into 2 phosphate groups as that is favourable and what drive the reaction in forward direction
how is the side reaction of hydrolyzing pyrophosphate important for acyl CoA molecule
the reaction of breaking the pyrophosphate intop 2 phosphate groups will drive the reaction of forming acyl CoA and keeping it from going back
what makes ATP–>AMP energetically favourable
this reaction is so efficient that it is responsible for 95% of the ATP made from oxidative phosphorylation as it uses ADP as subtrate since ATP synthase can only bind ADP where the reaction go as: AMP+ATP–>2ADP–>2ATP, where the first part is catalyzed by adenylate kinase and the second part is catalyzed by ATP synthase
what is the energy required for fatty acid activation by CoA
the process require 2ATP as one will be ised for activation and other to produce ADP and the enrgy to keep acyl CoA and 1water molecule will be needed to hydrolyze PPi
where does beta oxidation occur and how does it get to where it needs to
so acyl CoA is made in cytoplasm but beta oxidation occur inside matrix so the acyl CoA has to access the matrix but it cna only enter the mitochondrial inner memrbane by the porins and is too large and water soluble to cross into matrix so requires the help of shuttle
what is the way that carnitine shuttle allow for acyl CoA to get into matrix
the shuttle consist of two enzymes and a translocase where the carnitine acyltransferase I (CAT I) enzymes is found in cytoplasmic side while the carnitine acyltransferase II (CAT II) is found in the matrix side
the CAT I will convert carnitine into acyl carnitine by transfering the acyl group of acyl CoA to carnitine and then this acyl carnitine gets translocated into matrix side by translocase enzyme of the shuttle and once in matrix then CAT II will transfer the acyl group from acyl carnitine to CoA and make acyl CoA again and free carnitine to be reused
what is point of making the fatty acyl CoA outside the matrix if it is only used in matrix
the whole idea is about regulation since having permitivity will allow for membrane to stop and let molecules come in as seen appropriate
could carnitine supplements act as magic pill and promote weight loss
no because translocase protein is saturable meaning if carnitine exceed the threshold then that will cause bottlneck effect and excess carnitine gets ridden of due to body detecting excess carnitine