General Biochem 4 (pre-learning 1).pdf

Lipids Part 3a Prelearning: Lipolysis Dr. Rochelle Heisel BMS100 Lipogenesis Lipogenesis review: Storage of fatty acids as TG’s in liver and adipose Additional purpose of TG’s in liver: Combine with cholesterol, phospholipids and proteins to make lipoproteins Lipoproteins carry fatty acids and chole...

Lipids Part 3a Prelearning: Lipolysis Dr. Rochelle Heisel BMS100 Lipogenesis Lipogenesis review: Storage of fatty acids as TG’s in liver and adipose Additional purpose of TG’s in liver: Combine with cholesterol, phospholipids and proteins to make lipoproteins Lipoproteins carry fatty acids and cholesterol to tissues Fatty acids: used for energy Cholesterol: used for membranes and steroid hormones Lipolysis: Breakdown of TG’s to release free fatty acids and glycerol Adipose and liver: ffa’s used for energy Adipose: ffa’s released into blood and travel to liver Stored as TG’s then packaged into lipoproteins Energy Lipoproteins (FYI: VLDL) ffa’s + Glycerol-3-P Excess glucose TG’s (FYI: LDL) Glycerol ffa’s Liver β-ox Dietary fats: fatty acids packaged into chylomirons for transport to tissues Energy Glycerol TG’s Lipolysis ffa’s + Glycerol-3-P Lipogenesis Fatty acid synthesis Excess glucose Adipose Energy Extra-hepatic tissue (ex muscle) Lipolysis Sequential removal of fatty acids via hydrolysis TAG to DAG + ffa ATGL Enzyme = adipose triglyceride lipase HO DAG to MAG + ffa Enzyme = hormone sensitive lipase OH MAG to glycerol + ffa HSL Enzyme = monoglyceride lipase HO OH HO OH OH OH MGL OH Lipolysis What hormones regulate hormone-sensitive lipase (HSL)? Glucagon Insulin Epinephrine This should sound familiar…these are the same hormones that regulated fatty acid synthesis and beta oxidation. Review: how? Lipolysis Glucagon and epinephrine Increase beta ox Decrease fatty acid synthesis Insulin Decrease beta ox Increase fatty acid synthesis Trying to break down fa’s for energy, not make them. - HSL is activated to release fa’s from TG’s for energy. Have glucose for energy, want to make and store fa’s for later use. - HSL is inactivated so fa’s remain in storage as part of TG’s. Check your knowledge What can the liver do with TG’s, besides break them down? What is the purpose of this? What are the products of lipolysis? In general, what type of enzyme catalyzes hydrolysis of each fatty acid from the glycerol backbone? What 2 hormones activate HSL, and which hormone inhibits it? What is the rationale?