生物化学IILectureFattyacidmetabolismwebversion.pptVIP

Fatty acid metabolism – topics Role of lipases – breakdown of triglycerides and phospholipids Activation of fatty acids for the β-oxidation cycle (CoASH) Transport into the mitochondria (carnitine) β-oxidation pathway Even chain saturated FA Unsaturated FA Odd numbered FA Role of biotin and Vit B12 Energy calculations Starvation Energy sources for exercise Fatty acid oxidation-energy from lipids Long chain FA serve as main source for animals: FA are oxidized and broken down to AcCoA. The release of electrons (NADH) drives ATP synthesis ? Energy The production of AcCoA feeds the TCA cycle ? Energy Sources of FA: Diet Cell storage (lipid droplets) Synthesis (excess carbs, etc.) Fatty acid oxidation outline Lipases are produced in the pancreas Role of Lipases Breakdown of Triglycerides Triglycerides ingested ? water insoluble Emulsified by bile salts (detergents) in intestine Lipases break them down to fatty acids and glycerol which are taken up by intestinal mucosa Triglycerides stored in adipose tissue Broken down by lipases, triggered by hormonal signals (epinephrine, glucagon) Lipases Breakdown of phospholipids by phospholipases Phospholipases A (1 and 2), C, and D. Phospholipases important for intracellular signals Ex: Inositol triphosphate from Phosphotidyl inositol which is involved in signalling Ca+ release from ER (muscle contraction, other acitivties) Phospholipases also present in snake venom and wasp/bee poisons β-oxidation Sequential breakdown of fatty acids to yield AcCoA Occurs in mitochondria (like TCA) Series of 4 basic steps that are repeated over and over AcCoA produced ? TCA cycle ? CO2 and energy For a C16 we have 7 rounds of β-oxidation to yield: 8 AcCoA 7 NADH 7 FADH2 β-oxidation Palmitic acid (C16): C15H31COOH + 23 02 ? 16 CO2 + 16 H2O ?Go` = - 9773 KJ/mol Glucose (CH2O)6 + 6 O2 ? 6 CO2 + 6 H2O ?Go` = - 2868 KJ/mol Palmitic acid has many more carbons to oxidize and is much more reduced Β-oxidation-transport into mitochondria The fatty ac