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28 Cards in this Set
- Front
- Back
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What is the purpose of fatty acid synthesis? Where does it occur? What goes in/out? Regulation?
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Energy Storage
Location: Cytoplasm of hepatocytes Acetyl CoA-->Fatty Acids Regulation: Rapid control via AcCoa carboxylase |
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In what type of environment are fatty acids stored? What does this allow for?
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Non-aqueous environment; allows for large stores
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How do energy sources change from the fed state to post-absorptive state? 24 fast? 72 hour fast?
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Fed: Energy from diet
Post-Absorptive: Glycogen breakdown 24 hour fast: Gluconeogenesis 72 hour fast: FA oxidation (not as glucose!) |
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What are examples of esterified fatty acids? How are unesterified fatty acids transported in blood?
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Esterified: TG's, cholesterol ethers, phospholipids
Must circulate while bound to ALBUMIN |
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What are the essential fatty acids?
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Linoleic Acid and Linolenic Acid
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Describe the first step of fatty acid synthesis.
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Acetyl Group Shuttle:
Acetyl CoA from inside mitochondria to cytosol via Citrate |
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Describe the second step of FA synthesis.
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Malonyl CoA Synthesis:
RATE LIMITING STEP! Acetyl-CoA Carboxylase is RATE LIMITING ENZYME for FA Synthesis Regulated by insulin and counterregulatory hormones |
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What's the rate limiting enzyme for FA synthesis? How is it regulated?
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Acetyl CoA Carboxylase
Insulin, Norepi, Glucagon |
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Describe the third reaction of fatty acid synthesis. What's the energy source that drives this reaction?
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Malonyl-CoA + Acetyl CoA + NADPH-->Palmitate
Via Fatty Acid Synthetase Complex (REDUCTION REACTION!!!) Driven by NADPH (14 of them) from HEXOSE MONOPHOSPHATE PATHWAY |
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What is the fatty acid synthase complex? What is its overall reaction? Requirements?
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Complex of 7 enzymes that facilitate successive steps in FA synthesis
General: Lengthens FA by 2C's via REDUCTION REACTION!!! Requires acyl carrier protein (ACP) and Pantothenic acid (vitamin)--latter is what malonyl-coA binds |
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What steps occur after formation of Palmitate? Where do these steps occur?
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Elongation: ER and mitochondria in brain and adrenal gland
Desaturation: ER and catalyzed by oxidases |
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If vertebrates lack the enzyme to convert oleic acid to linoleic acid, how is this acid obtained?
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Through diet. It's an essential fatty acid. As is linolenic acid.
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Describe the three fatty acids esterified to glycerol.
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They're usually different, C1 saturated, C2 unsaturated, C3 can be either
It's complicated. |
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What two functions do white fat cells serve?
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Energy Storage
Metabolic functions: make cytokines (for inflammation) |
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What is the purpose of fatty acid degradation? Where does it occur? What goes in/out? Regulation?
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Purpose: Provision of energy
Location: mitochondria (it's oxidation) Dietary and Stored FA's-->CO2 + H2O + ENERGY (once completely oxidized) OR KETONE BODIES (in liver) Regulation: transport into mitochondria via carnitine shuttle |
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Describe the first step in fatty acid oxidation.
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Triacylglycerol (stored in fat cells)-->
Diacylglycerol + FFA--> Monoglyceride + FFA--> Glycerol + FFA All via Hormone-Sensitive Lipase: activated by cAMP-dependent kinase; inactivated by insulin |
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Describe the second step in fatty acid oxidation.
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Mitochondrial Transport in Liver Cell:
Outer mitochondrial membrane: RCOO- + CoA-SH+ATP-->RCO-S-CoA via Faty Acyl-CoA Synthase RCO-S-CoA + Carnitine--> RCO-Carnitine + CoA-SH Via CPT1 RCO-Carnitine + CoA-SH--> RCO-S-CoA in inner mitochondrial membrane via CPT II THIS IS THE REGULATORY POINT IN FATTY ACID OXIDATION!!!! |
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Why are only long-chain fats subject to regulation?
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Carnitine transport system is required for importing FA's of chain length longer than 12C's.
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What is the third step of FA oxidation?
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RCO-S-CoA + FAD-->Enoyl-S-CoA + FADH2
Via Acyl-CoA Dehydrogenase |
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Via what reaction is most energy derived from fat?
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beta-oxidation
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What do steps 4 to 7 of FA oxidation result in? Quantify this in terms of ATP.
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Enoyl-S-CoA-->-->-->8 acetyl-S-CoA + 7FADH2 + 7NADH + 7H+
2ATP per FADH2 3 ATP per NADH =35 ATP 8 acetyl=CoA-->96 ATP Total: 131 ATP per mole |
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Describe the steps of ketogenesis. When and where do these reacitons occur?
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How is ketogenesis triggered?
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In fasted state, have net flux of OAA-->Glucose (gluconeogenesis)
Decrease in OAA --> decreased acetylCoA used for citrate formation acetyl CoA then preferentially convereted to acetoacetate (AcAcCoA) So ketogenesis behaves as an overflow PW for AcCoa |
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What's the effect of carbohydrate availability on ketogenesis?
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Low cab availability-->increased hepatic ketogenesis
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Explain diabetic ketoacidosis.
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Lack of insulin stimulates lipolysis in periphery
Released TG's transported to liver where ketogenesis is fully activated Results in diabetic ketoacidosis |
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What's the purpose of alpha-oxidation? Location? In/out? Regulation? Clinical relevance?
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Purpose: metabolize Fa's that can't undergo direct beta-oxidation
Location: Peroxisomes FA (alpha-carbon is substrate for hydroxylation)-->alpha-OH FA's Regulation: Substrate-driven Clinical Note: Defective in REFSUM'S DISEASE |
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What's the purpose of omega-oxidation? Location? In/out? Regulation? Clinical notes?
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Purpose: Alternative metabolism of FA's
Location: Extra-mitochondrial (microsomal) In/Out: FA (omega-carbon)-->Dicarboxylic FA's REgulation: Substrate-driven Notes: Upregulated if beta-oxidation defective |
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What are symptoms of MCAD?
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Medium Chain Acyl-CoA DH Deficiency:
Fatty Liver No ketonuria Hypoglycemic Accumulation of medium chain fatty acids (octanedioic, nonanedioic, decanedioic acids) |
