Fat Metabolism

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

2. Digestion, Mobilization, and Transport • http://courses.cm.utexas.edu/emarcotte/ch339k/fall2005/Lecture-Ch17-1/Slide2.JPG

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

4. Chylomicron Carriers • proteins that carry fats • stored in adipose tissue

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

6. Animation of Process • http://www.wiley.com/legacy/college/boyer/0470003790/animations/fatty_acid_metabolism/fatty_acid_metabolism.htm • FUN!

7. Activation and Transported to Mitochondria • FA + CoASH --> ATP = FA-SCoA + AMP + Ppi • Driven by breakup of Ppi • Acyl CoA Synthetase • -32.5 kJ • Transported through inner mitochondrial membrane via carnitine • uses specific acyl carnitine transporter

8. Carnitine

9. Formation of acyl carnitine • Can get transported across inner mitochondrial membrane

10. Animation of Process • http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/carnitine/carnitine1.html

11. Beta Oxidation • Breakdown of fats into • Acetyl coenzyme A --> Krebs Cycle • FADH2 --> Oxidative Phosphorylation • NADH--> Oxidative Phosphorylation • Breaks off two carbons at a time to acetyl CoA • Remaining goes another round

12. Reactions Diagram

13. Reactions of Beta Oxidation Acyl-CoA Dehydrogenase • Puts in a ß double bond • Oxidizes C-C bond to double bond • Produces FADH2

14. Reactions of Beta oxidationEnoyl CoA Hydratase • adds water • forms ß-hydroxy product

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

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

17. Overall Per Beta Oxidation cycle • 1 FADH2…………………………1.5 ATP • 1 NADH………………………….2.5 ATP • 1 Acetyl CoA to Krebs • 3 NADH X 2.5 ATP / NADH………7.5 ATP • 1 FADH2…………………………….1.5 ATP • 1 GTP………………………………..1.0 ATP Total =14.0 ATP

18. Beta Oxidation on 16 C fatty Acid

19. Beta Oxidation on 16 C fatty Acid • 7 rounds of Beta oxidation (bottom numbers) • Form 8 acetyl Co A (top numbers)

20. Beta Oxidation on 16 C fatty Acidtotals • 7 rounds of beta oxidation 7 rounds X FADH2 X 1.5 ATP = 10.5 ATP round FADH2 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 FADH2 X 1.5 ATP = 12 ATP Krebs FADH2 8 Krebs X GTP X 1 ATP = 8 ATP Krebs GTP 1 ATP used to activate = - 1 ATP Total 107 ATP

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

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

23. 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. • http://www.biocarta.com/pathfiles/ketonebodiesPathway.asp

24. 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)

25. 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