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Flashcards by Marissa Alvarez, updated more than 1 year ago
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Created by Marissa Alvarez
almost 5 years ago
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| Question | Answer |
| ___ (__) is a coenzyme that forms a thioester with fatty acids Recall that __ ___ have a carboxylic acid group and an acyl group. ___ COA is required to synthesize fatty acids The rate-limiting step in fatty acid synthesis is the conversion of acetyl COA into ___ ___ | Coenzyme A (COA) fatty acids Acetyl COA malonyl COA |
| For fatty acid synthesis, the malonyl and acyl groups are bound by a thioester bond to an acyl carrier protein (___), instead of COA. Fatty acid chains are synthesized by adding ___ carbons at a time. There are 4 steps involved in growing a fatty acid chain by 2 carbons: 1) _________ 2) _________ 3) _________ 4) _________ | (ACP) two 1) Condensation 2) Reduction 3) Dehydration 4) Reduction |
| Consider an acyl chain 10 carbons long, extended to a 12 carbon acyl chain Four steps l. Condensation 2. Reduction 3. Dehydration 4. Reduction Repeated to make longer fatty acid Each reduction step requires ___ | NADPH |
| Review functions of lipids _____ — e.g. plasma membrane — glycerophospholipids, sphingolipids, and cholesterol Storage of energy — ____ Insulation Protection of surface - ___ Regulation of metabolism - ____ Regulation of blood pressure, temperature, and contraction - ____ Cell recognition - ______ | Structure triacylglycerols waxes steroids eicosanoids glycosphingolipids |
| Goals | ->Learn the biomolecules required to synthesize fatty acids ->Understand the 4 repeated reactions required to lengthen an acyl chain by 2 carbons ->Learn key enzymes and how fatty acid synthesis is regulated ->Understand how fatty acids are activated and the role of elongases and desaturases ->Understand pathways to make triacylglycerol and glycerophospholipids from fatty acids (including key intermediates) and the requirement for CTP |
| Fatty acid synthesis Needs carbon — ____ __ — from the glycolytic and citric acid cycle — citrate is major source Needs reducing power — ___ — from the pentose phosphate pathway Occurs in ____ | acetyl COA NADPH cytoplasm |
| Fatty acids are synthesized and degraded by adding or removing __ carbons at a time. For fatty acid synthesis Four repeating steps — condensation, reduction, dehydration and reduction then ___ | 2 repeat |
| Acyl groups are linked to ___ or ___ Build = ___ ___ Degrade = ___ ____ | COA or ACP malonyl ACP acetyl CoA |
| ___-__ is the substrate for fatty acid biosynthesis Malonyl COA is generated from acetyl COA and bicarbonate. Catalyzed by ___-___ ___ Irreversible reaction *key to ____ Malonate group transferred to acyl carrier protein (ACP) ->Linked via ____ | Malonyl-ACP acetyl-CoA carboxylase (ACC) regulation thioester |
| 1st step = ______ First step is the generation of ____ ACP from acetyl ACP and malonyl ACP Malonyl ACP only adds _ carbons at a time BUT acetyl ACP can have __ number of carbons to combine to malonyl ACP | Condensation acetoacetyl (OR ketoacetyl) 2 any |
| Fatty acid synthesis is catalyzed by ___ ___ __ (__ _) ->In eukaryotes it is a dimer of large 2500 amino acid proteins Fatty acid synthesis occurs in the ___ | fatty acid synthase (FAS I) cytoplasm |
| __ and __ carbon fatty acids are made in eukaryotes longer side chains don't fit Our enzyme can only accommodate 16 & 18 Carbon FA's (___ doesn’t fit) Fatty acid synthesis is energy ____, I palmitate — important to regulate 178 ATP to make | 16 & 18 longer expensive |
| Regulation of fatty acid synthesis by regulation of ACC activity | |
| Free fatty acids — some are found but they are mostly incorporated into ____. Free fatty acids must be ____ before they can be used. Forms a ___ with CoA. Activated because of high ___ bond (covalent attachment) | lipids activated thioester energy |
| Modifications to fatty acids How to make longer? ->___e xtend fatty acid by 2 carbons ->Uses ___ COA to extend How to make unsaturated? ->In eukaryotes ___ form double bonds ->Unsaturated fatty acids are synthesized ___, then desaturated. ->In prokaryotes — uses __ __ — this enzyme can partially synthesize a fatty acid, create a double bond, then continue synthesis of the fatty acid | Elongases malonyl desaturases first FAS II |
| Example of elongation and desaturation ____ fatty acid — must come from the diet (note is activated here) Desaturase introduces ___ bond-oxidation-consumes NADH - molecular oxygen is ___ Elongation — ___ COA is used to add 2 more carbons Reduction/dehydration/reduction step occurs-consumes ___ Desaturase introduces double bond-oxidation - molecular oxygen is reduced | Essential double reduced malonyl NADH |
| Most fatty acids are incorporated into triacylglycerol or glycerophospholipids ->2 acyl groups from acyl COA molecules are transferred to glycerol 3- phosphate ->____ is the product ->____ is intermediate to make triacylglycerols or glycerophospholipids | Phosphatidate Phosphatidate |
| How to make triacylglycerol? l. Remove the phosphate from phosphatidate forming ___ (__) 2. Transfer acyl group from ___ ___ to the alcohol group of DAG | diacylglycerol (DAG) acyl COA |
| How to make glycerophospholipids? Step I — CTP reacts with alcohol phosphate to form a nucleotide alcohol derivative Need __ (a nucleotide) to make glycerophospholipid as an energy source | CTP |
| How to make some glycerophospholipids? l. React __ with alcohol phosphate 2. Remove the phosphate from phosphatidate forming ___ (__) 3. Transfer the group from the nucleotide alcohol derivative to the alcohol group of DAG releasing CMP to generate _____ (PC) or ______ (PE) | CTP diacylglycerol (DAG) phosphatidylcholine phosphatidylethanolamine |
| How to make phosphatidylserine? In most eukaryotes: phosphatidyl_____: serine Phosphatidylethanolamine transferase exchanges the ____ with serine to generate phosphatidylserine (PS) | ethanolamine ethanolamine |
| How to make other glycerophospholipids? l. React CTP with phosphatidate to form ___-____ 2. React CDP-diacylglycerol with serine or ____ to generate phosphatidylserine (PS) or _____ (__) respectively | CDP-diacylglycerol phosphatidylinositol (PI) |
| Recap ->___ & ___ are required for fatty acid synthesis ->Generation of malonyl COA by ___ ___ (__) is a key regulatory reaction ->____ catalyzes condensation (addition of 2 carbons), reduction, dehydration and reduction reactions in fatty acid synthesis ->Major products of FAS I can be elongated and/or ____ ->Fatty acids are activated by ___ ->Fatty acids are ___ as triacylglycerols or used to synthesize glycerophospholipids ->____ is key intermediate and a nucleotide (__) alcohol derivative is required for synthesis of glycerophospholipids | Acetyl COA and NADPH acetyl COA carboxylase (ACC) Fatty acid synthase I (FAS I) desaturated CoA stored Phosphatidate CDP |
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