Fat Metabolism I’m not fat, I’ve just got a lot of potential energy!

Digestion, Mobilization, and Transport

Emulsification Fats are not water soluble Made into bile salts that are Absorbed as micelles in small intestines

Chylomicron Carriers proteins that carry fats stored in adipose tissue

Role of Hormones Can mobilize from adipose Release as Fatty acids Epinephrene and glucagon release cAMP –make fatty acids and glycerol –mobilizes fat

Animation of Process / /animations/fatty_acid_metabo lism/fatty_acid_metabolism.htmhttp:// / /animations/fatty_acid_metabo lism/fatty_acid_metabolism.htm FUN!

Activation and Transported to Mitochondria FA + CoASH --> ATP = FA-SCoA + AMP + Ppi Driven by breakup of Ppi Acyl CoA Synthetase kJ Transported through inner mitochondrial membrane via carnitine –uses specific acyl carnitine transporter

Carnitine

Formation of acyl carnitine Can get transported across inner mitochondrial membrane

Animation of Process mplates/student_resources/shared_resources /animations/carnitine/carnitine1.htmlhttp:// mplates/student_resources/shared_resources /animations/carnitine/carnitine1.html

Beta Oxidation Breakdown of fats into –Acetyl coenzyme A --> Krebs Cycle –FADH 2 --> Oxidative Phosphorylation –NADH--> Oxidative Phosphorylation Breaks off two carbons at a time to acetyl CoA –Remaining goes another round

Reactions Diagram

Reactions of Beta Oxidation Acyl-CoA Dehydrogenase –Puts in a ß double bond Oxidizes C-C bond to double bond –Produces FADH 2

Reactions of Beta oxidation Enoyl CoA Hydratase adds water –forms ß-hydroxy product

Reactions of Beta Oxidation ß-hydroxylacyl-CoA dehydrogenase oxidizes secondary alcohol to ketone –Oxygen-containing group –Produces NADH

Reactions of Beta Oxidation Acyl-CoA acetyltransferase (thiolase) Uses another CoA Produces Acetyl CoA Acyl CoA can go another round

Overall Per Beta Oxidation cycle 1 FADH 2 …………………………1.5 ATP 1 NADH………………………….2.5 ATP 1 Acetyl CoA to Krebs –3 NADH X 2.5 ATP / NADH………7.5 ATP –1 FADH 2 …………………………….1.5 ATP –1 GTP………………………………..1.0 ATP Total = 14.0 ATP

Beta Oxidation on 16 C fatty Acid

7 rounds of Beta oxidation (bottom numbers) Form 8 acetyl Co A (top numbers)

Beta Oxidation on 16 C fatty Acid totals 7 rounds of beta oxidation 7 rounds X FADH 2 X 1.5 ATP = 10.5 ATP round FADH 2 7 rounds X NADH X 2.5 ATP = 17.5 ATP round NADH 8 acetyl CoA 8 Krebs 8 Krebs X 3 NADH X 2.5 ATP = 60 ATP Krebs NADH 8 Krebs X FADH 2 X 1.5 ATP = 12 ATP Krebs FADH 2 8 Krebs X GTP X 1 ATP = 8 ATP Krebs GTP 1 ATP used to activate = - 1 ATP Total107 ATP

Unsaturated Fat Metabolism special enzymes needed to convert cis bonds in fatty acids to trans bonds

Regulation of Fat Metabolism Transport is rate-limiting Regulation of carnitine acyl transferase –off by fat synth products –high NADH

Ketone Bodies Starvation causes accumulation of acetyl CoA –not enough carbohydrates to keep Kreb’s Cycle going –acetyl CoA forms acetoacetate, b- hydroxybutyrate, and acetone. diesPathway.asphttp:// diesPathway.asp

Diabetes and Ketone Bodies When there is not enough insulin in the blood and it must break down fat for its energy. Ketones build up in the blood and then spill over into the urine so that the body can get rid of them. Acetone can be exhaled through the lungs. This gives the breath a fruity odor. Ketones that build up in the body for a long time lead to serious illness and coma. (Diabetic ketoacidosis)

Comparison of Fat Metabolism per gram and CHO per gram Fats provide about 9 kilocalories per gram and carbohydrates provide about 4 kilocalories per gram. Using nutritional units, that is 9 Calories/gram for fats and 4 Calories/gram for carbohydrates. CHO provide energy more quickly Fats are good fuel for endurance events, but not sprints