Biochem lipid metab

• Lipids - represent an efficient way of storing chemical energy
• Metabolic oxidation of lipids releases large quantities

  of energy through production of acetyl-CoA, NADH,

  and FADH2
• Oxidation of fatty acids is the chief source of energy
• lipids that are sterols (steroids that have a hydroxyl group as part of their structure) are not catabolized as a source of energy but are excreted.
• Triacylglycerol - Main storage form of the chemical

  energy for most organisms
• • Carbon chains are in a highly reduced form
  • Energy yield per gram of fatty acid oxidized is greater

  than that per gram of carbohydrate oxidized
• Phosphoacylglycerol - Key component

  of biological membranes

  • May have multiple sites of action
• label phospholipase

  A) A1

  B) A2

  C) C

  D) D

  
• • Triacylglycerols and phosphoacylglycerols

  • Have fatty acids as part of their covalently bonded

  structures

  • Bond between the fatty acid and the rest of the

  molecule can be hydrolyzed

  • Lipases: Hydrolyze lipids (Triacylglycerols)

  • Phospholipases: Hydrolyze phospholipids (Phosphoacylglycerols)
• Label

  A) Triacyglycerol

  B) Phosphatidylcholine

  C) Glycerylphosphorylcholine

  D) Reuse or oxidation

  E) Glycerol

  F) Lipases

  G) Phospholipases

  
• Release of Fatty Acids from Triacylglycerols in Adipose Tissue Is Hormone-Dependent
• Rank The process:

  1. Hormone binds to a receptor on the plasma membrane of the adipocyte.
  2. This hormone binding activates adenylate cyclase, which leads to production of active protein kinase A (cAMP-dependent protein kinase).
  3. Protein kinase phosphorylates triacylglycerol lipase, which cleaves the fatty acids from the glycerol backbone. The main hormone that has this effect is epinephrine. Caffeine also mimics epinephrine in this regard
• • Fatty acid oxidation begins with activation of the

  molecule

  • Activation in lipid metabolism: Thioester bond is

  formed between the carboxyl group of the fatty acids

  and the thiol group of CoA-SH

  • Acyl-CoA synthetase catalyzes formation of the ester

  bond and requires ATP for its action

  • Esterification takes place in cytosol, but the rest of

  the reactions of fatty acid oxidation occur in the

  mitochondrial matrix

  • Acyl-CoA can cross the outer mitochondrial

  membrane but not the inner membrane