Fat Digestion and Metabolism PDF

Fat digestion and metabolisms Fat metabolism including forth stage : 1. Fat digestion 2. Fat absorption 3. Fat storage 4. Fat oxidation Definition of oxidation A. Fat oxidation: is most important method to produce energy in man a...

Fat digestion and metabolisms Fat metabolism including forth stage : 1. Fat digestion 2. Fat absorption 3. Fat storage 4. Fat oxidation Definition of oxidation A. Fat oxidation: is most important method to produce energy in man and animals from neutral storage fat. B. Neutral fat have high energy in oxidation yield about ( 9 kilocalorie /gm ) compare to glycogen that yield ( 4 kilocalorie /gm ). Stages of fat Digestion and transportation 1. fat digestion :.In stomach : a. Sold Fat and cholesterol emulsified by heat of stomach and acidic gastric juice and gastric lipase enzymes then move this acidic emulsification to small intestine. 2. fat absorption : a.In small intestine: 1. (Alkaline) Bile juice convert (Acidic )emulsified fat and triacylglycerol into neutral mixed micelles 2. , pancreatic lipase enzyme also, lysis these micelles into simple fatty acids in order to facilitate absorption by intestinal mucosa b.In intestinal mucosa : 1. Simple fatty acids which absorbed converted again into triacylglycerol 2. Triacylglycerol + cholesterol + incorporated with Appoprotein to form chylomicrons (lipoprotein the transporter) which moving it through lymphatic vessels to blood vessels to hepatic tissue cells. 1 c. lipid storage in fat tissues 1. Lipoprotein lipase enzyme lysis chylomicron ( large molecules ) and convert triglycerides into ( small particles) free fatty acids and glycerol. 2. In order to facilitate transportation and storage fats as a triglyceridea again in myocytes and Adiopcyte. 4.lipid oxidation (beta oxidation ) 1. In case of requirement to energy / triglycerides lysis , release free fatty acids and glycerol as a responses to glucagon and Epinephrine hormones 2. fats move from adipose tissues via blood stream in order to distributed to tissue cells in needs in which oxidized by beta –oxidation reaction as a fuel in the mitochondria of these cells. FAT digestion transformation and metabolism 2  Lipoprotein structure (chylomicrone ) -Beta oxidation rreaction Befor oxidation : Fat enter to cell cytoplasm and before entering the mitochondria to start oxidation two steps must be done : 1. Activation of fatty acids This activation is occur in cytoplasm by reaction fatty acids with Co- enzyme- A to formed fatty acid acyle Co-A : Fatty Acid + Co-ASH ------------> ATP = Fatty Acyle -SCo-A + AMP ((Acyl CoA Synthetase)) 2. reaction with Carnitine transporter Fatty Acyle -SCo-A which yielded transported through inner mitochondrial membrane accompanied with carnitine : form acyl carnitine transporter 3 Beta-oxidation reaction : There are four stages of beta- oxidation reaction : ATP of Beta Oxidation Per n FAD-dependent dehydrogenation n Hydration n NAD-dependent dehydrogenation n cleavage each cycle: 1 Acetyl CoA in Krebs: – 3 NADH X 3 ATP / NADH………9 ATP – 1 FADH2…………………………….2 ATP – 1 ATP………………………………..1.0 ATP Total = 17.0 ATP Beta Oxidation on 16 C fatty Acid O CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 C O Beta Oxidation on 16 C fatty Acid ( EX. PALMITIC ACID) 1 2 3 4 8 5 6 7 O CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 C O 3 7 6 4 5 1 2 7 rounds of Beta oxidation Form 8 acetyl Co A Beta Oxidation on 16 C fatty Acid : EX.PALMITIC ACID totals 8 acetyl CoA IN 8 Krebs 4 8 Krebs X 3 NADH X 3 ATP = 72 ATP ((Krebs NADH )) 8 Krebs X FADH2 X 2 ATP = 16 ATP ((Krebs FADH2 )) 8 Krebs X GTP X 1 ATP = 8 ATP ((Krebs ATP)) 7 rounds of beta oxidation: 7 rounds X FADH2 X 2 ATP = 14 ATP (( round FADH2)) 7 rounds X NADH X 3ATP = 21 ATP (( round NADH)) 2 ATP used to activate = - 2 ATP Total 129 ATP = (131-2) IN Unsaturated Fat Metabolism special enzymes needed to convert cis DOUBLE bonds in fatty acids to trans bonds. Assist prof. Dr Majid Joudah uaibi 29-5-2021 5