Adenosine triphosphate fatty acid oxidation

The complete oxidation of a single fatty acid molecule produces a large quantity of energy. For example, the complete oxidation of 1 mole of palmitic acid to carbon dioxide and water produces 16 moles of CO2, 16 moles of H2O, and 129 moles of adenosine triphosphate (ATP), or 2340 Thus the standard free energy for oxidation of palmitic acid is 2340 Cal, whereas the free energy liberated by hydrolysis of 129 moles of ATP is 940 Cal, indicating that the efficiency of energy conservation in fatty acid oxidation is approximately 40% under standard conditions. 

The Krebs cycle is a series of enzymatic reactions that catalyzes the aerobic metabolism of fuel molecules to carbon dioxide and water, thereby generating energy for the production of adenosine triphosphate (ATP) molecules. The Krebs cycle is so named because much of its elucidation was the work of the British biochemist Hans Krebs. Many types of fuel molecules can be drawn into and utilized by the cycle, including acetyl coenzyme A (acetyl CoA), derived from glycolysis or fatty acid oxidation. Some amino acids are metabolized via the enzymatic reactions of the Krebs cycle. In eukaryotic cells, all but one of the enzymes catalyzing the reactions of the Krebs cycle are found in the mitochondrial matrixes. 

Phosphorus. Eighty-five percent of the phosphoms, the second most abundant element in the human body, is located in bones and teeth (24,35). Whereas there is constant exchange of calcium and phosphoms between bones and blood, there is very Httle turnover in teeth (25). The Ca P ratio in bones is constant at about 2 1. Every tissue and cell contains phosphoms, generally as a salt or ester of mono-, di-, or tribasic phosphoric acid, as phosphoHpids, or as phosphorylated sugars (24). Phosphoms is involved in a large number and wide variety of metaboHc functions. Examples are carbohydrate metaboHsm (36,37), adenosine triphosphate (ATP) from fatty acid metaboHsm (38), and oxidative phosphorylation (36,39). Common food sources rich in phosphoms are Hsted in Table 5 (see also Phosphorus compounds). 

Subsequently, the functions of the vitamin were better established and requirements for the vitamin were set. Riboflavin is an Integral part of two coenzymes, flavin-5 -phosphate (FMN) and flavin adenine dinucleotide (FAD), which function in oxidation/reductlon reactions. Indeed, riboflavin is an enzyme cofactor which is necessary in metabolic processes in which oxidation of glucose or fatty acid is used for production of adenosine triphosphate (ATP) as well as in reactions in which oxidation of amino acids is accomplished. The minimum requirement for riboflavin has been established as that amount which actually prevents the signs of deficiency. A range of intakes varying from 0.55 to 0.75 mg/day of riboflavin has been established as the minimum amount which is required to prevent appearance of deficiency signs. 

Eugene Kennedy and Albert Lehninger showed in 1949 that fatty acids are oxidized in mitochondria. Subsequent work demonstrated that they are activated before they enter the mitochondrial matrix. Adenosine triphosphate (ATP) drives the formation of a thioester linkage between the carboxyl group of a fatty acid and the sulfhydryl group of CoA. This activation reaction takes place on the outer mitochondrial membrane, where it is catalyzed by acyl CoA synthetase (also called fatty acid thiokinase). 

Fatty acids serve as a fuel for muscle, kidney, and most other tissues. They are oxidized to acetyl CoA, and subsequently to CO2 and H2O in the TCA cycle, producing energy in the form of adenosine triphosphate (ATP). In addition to the ATP required to maintain cellular integrity, muscle uses ATP for contraction, and the kidney uses it for urinary transport processes. 

Under aerobic conditions, in which most cells grow, mitochondria are the site of (i) the tricarboxylic acid cycle which transforms (to carbon dioxide, water, and energy) the acetyl-CoA which is produced by the metabolism of both carbohydrates and fatty acids (ii) the enzymes that oxidize and convert fatty acids to acetyl-CoA (iii) the respiratory-chain enzymes which transmit, to atmospheric oxygen, the electrons removed from all the various metabolic substrates, and store part of the energy, obtained in this way, as adenosine triphosphate. The enzymes of carbohydrate glycolysis (the Meyerhof sequence) are in the cytoplasm. 

Minute spheres, rods, or filaments in the cytoplasm. Mitochondria are the sites of numerous biochemical reactions including amino acid and fatty acid catabolism, the oxidative reactions of the KreE)s cycle, respiratory electron transport, and oxidative phosphorylation. As a result of these reactions, mitochondria are the major producers of the high energy compound adenosine triphosphate (ATP) in aerobically grown cells. 

The principal function of the oxidation of carbohydrates and fatty acids is to make available to the cells the free energy released in the oxidation process, in a form physiologically usable for cellular energy processes, viz, ATP. This is accomplished by the process known as oxidative phosphorylation, whereby adenosine triphosphate (ATP) with three phosphate groups, two of which are held by high energy bonds, is formed from adenosine diphosphate (ADP) by the addition of phosphate. 

Carnitine serves as a cofactor for several enzymes, including carnitine translo-case and acyl carnitine transferases I and II, which are essential for the movement of activated long-chain fatty acids from the cytoplasm into the mitochondria (Figure 11.2). The translocation of fatty acids (FAs) is critical for the genaation of adenosine triphosphate (ATP) within skeletal muscle, via 3-oxidation. These activated FAs become esterified to acylcamitines with carnitine via camitine-acyl-transferase I (CAT I) in the outer mitochondrial membrane. Acylcamitines can easily permeate the membrane of the mitochondria and are translocated across the membrane by carnitine translocase. Carnitine s actions are not yet complete because the mitochondrion has two membranes to cross thus, through the action of CAT II, the acylcar-nitines are converted back to acyl-CoA and carnitine. Acyl-CoA can be used to generate ATP via 3-oxidation, Krebs cycle, and the electron transport chain. Carnitine is recycled to the cytoplasm for fumre use. 

FA, fatty acid FADHj, reduced form of flavine adenine dinucleotide GTP, guanosine triphosphate NADH, reduced form of nicotinamide adenine dinucleotide ATP, adenosine triphosphate NAD3 oxidized form of nicotinamide adenine dinucleotide FAD, flavine adenine dinucleotide TAG, triacylglycerol... 

---