Carbohydrates


Keeton J. T. , BENLİ H. , Claflin A. E.

Handbook of Muscle Foods Analysıs, NOLLET L.M.L., TOLDRÁ F., Editör, Crc Press, New York, ss.263-277, 2009

  • Basım Tarihi: 2009
  • Yayınevi: Crc Press
  • Basıldığı Şehir: New York
  • Sayfa Sayıları: ss.263-277
  • Editörler: NOLLET L.M.L., TOLDRÁ F., Editör

Özet

Simple carbohydrates serve as the primary source of readily available energy for muscle cell metabolism, while more complex forms serve as structural components for a variety of tissues, organs, and organelles. Polysaccharides or glycans are covalently linked polymeric monosaccharide units that can be hundreds of units in length, and are further subdivided into homopolysaccharides (glycogen, starch, cellulose) and heteropolysaccharides (glycoproteins, proteoglycans, glycosaminoglycans, glycolipids). In antemortem muscle tissue and liver, the predominant storage form of glucose is the branched polysaccharide glycogen, which provides an easily metabolized energy source for muscle contraction and relaxation. When needed for muscle contraction, stored glycogen is readily converted to glucose-6-phosphate for further hydrolysis to glucose and entry into the glycolysis pathway. Subsequent metabolism follows through either an oxidative or an anaerobic pathway. At death, glycogen undergoes anaerobic glycolysis, terminating with the formation of lactate +oxidized nicotinamide adenine dinucleotide (NAD+) from pyruvate and NADH (reduced form) via LDH. A corresponding pH decline from approximately 7.0 to 5.6–5.8 occurs as a consequence of the buildup of lactate and hydrogen ions. Glycogen is generally analyzed by acid or enzymatic hydrolysis followed by glucose determination. ?-(+)-Lactate is typically enzymatically oxidized to pyruvate by NAD+ and catalyzed by LDH. Th e NADH formed is proportional to the amount of lactate present and is measured spectrophotometrically or fl uorimetrically. Traditional protein and carbohydrate techniques of selective precipitation, ion-exchange chromatography, zone electrophoresis, and gel fi ltration have been applied to fractionation methods for glycoproteins and proteolgycans.

Simple carbohydrates serve as the primary source of readily available energy for muscle cell metabolism, while more complex forms serve as structural components for a variety of tissues, organs, and organelles. Polysaccharides or glycans are covalently linked polymeric monosaccharide units that can be hundreds of units in length, and are further subdivided into homopolysaccharides (glycogen, starch, cellulose) and heteropolysaccharides (glycoproteins, proteoglycans, glycosaminoglycans, glycolipids). In antemortem muscle tissue and liver, the predominant storage form of glucose is the branched polysaccharide glycogen, which provides an easily metabolized energy source for muscle contraction and relaxation. When needed for muscle contraction, stored glycogen is readily converted to glucose-6-phosphate for further hydrolysis to glucose and entry into the glycolysis pathway. Subsequent metabolism follows through either an oxidative or an anaerobic pathway. At death, glycogen undergoes anaerobic glycolysis, terminating with the formation of lactate +oxidized nicotinamide adenine dinucleotide (NAD+) from pyruvate and NADH (reduced form) via LDH. A corresponding pH decline from approximately 7.0 to 5.6–5.8 occurs as a consequence of the buildup of lactate and hydrogen ions. Glycogen is generally analyzed by acid or enzymatic hydrolysis followed by glucose determination. ?-(+)-Lactate is typically enzymatically oxidized to pyruvate by NAD+ and catalyzed by LDH. Th e NADH formed is proportional to the amount of lactate present and is measured spectrophotometrically or fl uorimetrically. Traditional protein and carbohydrate techniques of selective precipitation, ion-exchange chromatography, zone electrophoresis, and gel fi ltration have been applied to fractionation methods for glycoproteins and proteolgycans.