الشحميات ٤. أكسدة الدسم في الا نسجة: الدكتورة درر الصوفي( ٤ ) عدد الصفحات( ١٣ ) CO2 anhydrous ATP. o o. Wikipedia.com

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1 8 H الشحميات ٤. الدكتورة درر الصوفي( ٤ ) عدد الصفحات( ١٣ ) 1 أكسدة الدسم في الا نسجة: CO2anhydrous ATP o o Wikipedia.com Fatty acids, stored as triglycerides in an organism, are an important source of energy because they are both reduced and anhydrous. The energy yield from a gram of fatty acids is approximately 9 Kcal (37 kj), compared to 4 Kcal/g for carbohydrates. Since the hydrocarbon portion of fatty acids is hydrophobic, these molecules, can be stored in a relatively anhydrous (water free) environment. Carbohydrates, on the other hand, are more highly hydrated. For example, 1 g of glycogen can bind approximately 2 g of water, which translates to 1.33 Kcal/g (4 Kcal/3 g). This means that fatty acids can hold more than six times the amount of energy. Put another way, if the human body relied on carbohydrates to store energy, then a person would need to carry (31 kg) of hydrated glycogen to have the energy equivalent to (5 kg) of fat.

2 أكسدة الغليسيرول: ATP. DHAPTGsTAGs Revision: o o أكسدة الحمض الدسم: Ωαβ : الا كسدة بيتا β 2

3 مراحل تحول البنزوي يك إلى هيباريك : ATPAcetyl CoA A Benzoic Acid CoA.SH ATP + Mg ++ + Glycine Benzoyl Co-A Hippuric Acid (benzoylglycine) بالنسبة لفينيل حمض الخل :phenylacetic acid AATP A 3

4 س: أین تتم الا كسدة البتاي یة الا كسدة بیتا في المتقدرات. Revision: fatty acid-binding protein Acyl -Co AAcetyl Co AATP {Acyl CoA synthetase)a} Acyl Co A Acyl Co A 4

5 CO-AAcyl-CoA A A Co-A CPT-II Revision: Acyl - Co a 5

6 Sources of carnitine (Lippincott s pg 189): Carnitine can be obtained from the diet,where it is found primarily in meat products. Carnitine can also be synthesized from the amino acids lysine and methionine by an enzymatic pathway found in the liver and kidney but not in skeletal or heart muscle. Therefore, these tissues are totally dependent on carnitine provided by hepatocytes or the diet, and distributed by the blood. [Note: Skeletal muscle contains about 97 percent of all carnitine in the body.] Carnitine deficiencies: Such deficiencies result in a decreased ability of tissues to use LCFA (long chain fatty acids) as a metabolic fuel, and it can also cause the accumulation of toxic amounts of free fatty acids and branched-chain acyl groups in cells. Secondary carnitine deficiency occurs for many reasons, including 1) in patients with liver disease causing decreased synthesis of carnitine, 2) in individuals suffering from malnutrition or those on strictly vegetarian diets, 3) in those with an increased requirement for carnitine as a result of, for example, to pregnancy, severe infections, burns, or trauma, or 4) in those undergoing hemodialysis, which removes carnitine from the blood. A FAD A FADH 2 A Revision: Enol Acyl Co-A A Enol acyl hydratase. Aβ β- hydroxy acyl Co-A 6

7 NADAβ NADHAβ A β A A A Revision: -OXIDATION OF FATTY ACIDSINVOLVES SUCCESSIVE CLEAVAGEWITH RELEASE OF ACETYL-CoA In βoxidation (Figure 22 2), two carbons at a time are cleaved from acyl-coa molecules, starting at the carboxyl end. The chain is broken between the α2)- and β(3)-carbon atoms hence the name βoxidation. The two-carbon units formed are acetyl-coa; thus, palmitoyl- CoA forms eight acetyl-coa molecules. 7

8 Oxidation of Fatty Acids Producesa Large Quantity of ATP(important) Transport in the respiratory chain of electrons from FADH2 and NADH will lead to the synthesis of five highenergy phosphates for each of the first seven acetyl-coa molecules formed by β oxidation of palmitate (7 5 = 35). A total of 8 mol of acetyl- CoA is formed, and each will give rise to 12 mol of ATP on oxidation in the citric acid cycle, making 8 12 = 96 mol. Two must be subtracted for the initial activation of the fatty acid, yielding a net gain of 129 mol of ATP per mole of palmitate, or * = 6656 kj. This represents 68% of the free energy of combustion of palmitic acid. الا كسدة ألفا: β CO2 8

9 NADCO2 (decarboxylation) R-CHOH-COOH R-CO-COOH (α-hydroxy acid) (α-keto acid) Revision: 9

10 Note: Refsum disease is a rare, autosomal recessive disorder caused by a deficiency of α- hydroxylase. This results in the accumulation of phytanic acid in the plasma and tissues. The symptoms are primarily neurologic, and the treatment involves dietary restriction to halt disease progression.] الا كسدة أوميغا: NADPH 2 β AAβ 10

11 : AAβ A A V.B8ATPCO2 A AV.B12 A Oxidation of a Fatty Acid With an OddNumber of Carbon Atoms Yields Acetyl-CoA Plus a Molecule of Propionyl-CoA Fatty acids with an odd number of carbon atoms are oxidizedby the pathway of βoxidation, producing acetyl- CoA, until a three-carbon (propionyl-coa) residue remains. This compound is converted to succinyl-coa, a constituent of the citric acid cycle. Hence, the propionyl residue from an odd-chain fatty acid isthe only part of a fatty acid that is glucogenic A AA 11

12 i 12

13 Biochemistry RBCs Team. درر اﻟﺼﻮﻓﻲ. د 13

OVERVIEW M ET AB OL IS M OF FR EE FA TT Y AC ID S

OVERVIEW M ET AB OL IS M OF FR EE FA TT Y AC ID S LIPOLYSIS LIPOLYSIS OVERVIEW CATABOLISM OF FREE FATTY ACIDS Nonesterified fatty acids Source:- (a) breakdown of TAG in adipose tissue (b) action of Lipoprotein lipase on plasma TAG Combined with Albumin