By I. Sobota. Massachusetts Maritime Academy.
In bone the enzyme is found in osteoblasts and is probably 20 important for normal bone function order generic unisom on-line. Serum alkaline phosphatase levels may be increase in congestive heart failure result of injury to the liver cheap generic unisom uk. It is present in high concentration in liver and to a lesser extent in skeletal muscle buy unisom 25mg visa, kidney and heart. It is widely distributed with high concentrations in the heart, skeletal muscle, liver, kidney, brain and erythrocytes. The enzyme is increased in plasma in myocardial infarction, acute leukemias, generalized carcinomatosis and in acute hepatitis. Estimation of it isoenzymes is more useful in clinical diagnosis to differentiate hepatic disease and myocardial infarction. Measurement of serum creatine phosphokinase activity is of value in the diagnosis of disorders affecting skeletal and cardiac muscle. Carbohydrates in general are polyhydroxy aldehydes or ketones or compounds which give these substances on hydrolysis. Chemistry of Carbohydrates Classification and Structure Classification There are three major classes of carbohydrates • Monosaccharides (Greek, mono = one) • Oligosaccharides (Greek, oligo= few) 2-10 monosaccharide units. The most abundant monosaccharides in nature are the 6-carbon sugars like D- glucose and fructose. One of the carbon atoms is double bonded to an oxygen atom to form carbonyl group. Structure of Glucose Open chain D-glucose α-D –glucose α-D –glucose (Fisher formula) (Haworth formula) Fig. Monosaccharides having aldehyde groups are called Aldoses and monosaccharides with Ketone group are Ketoses. Depending on the number of carbon atoms, the monosaccharides are named trioses (C3), tetroses (C4), pentoses (C5), hexoses (C6), heptoses (C7). No of carbon atoms Generic name Aldose family Ketose family 3 Triose Aldotriose Ketotriose Eg. Asymmetric Center and Stereoisomerism Asymmetric carbon is a carbon that has four different groups or atoms attached to it and having optically activity in solution. All the monosaccharides except dihydroxyacetone contain one or more asymmetric or chiral carbon atoms and thus occur in optically active isomeric forms. Monosaccharides with n number n of asymmetric centers will have (2 ) isomeric forms. The designation of a sugar isomer as the D- form or of its mirror images the L- form is determined by the spatial relationship to the parent compound of the carbohydrate family. When a beam of plane- polarized light is passed through a solution of carbohydrate it will rotate the light either to right or to left. Depending on the rotation, molecules are called dextrorotatory (+) (d) or levorotatory (-) (l). When equal amounts of D 25 and L isomers are present, the resulting mixture has no optical activity, since the activities of each isomer cancel one another. Epimers When sugars are different from one another, only in configuration with regard to a single carbon atom (around one carbon atom) they are called epimers of each other. The resulting six membered ring is called pyranose because of its similarity to organic molecule Pyran. This five membered ring is called furanose because of its similarity to organic molecule furan Fig 2. Glycosidic bond is formed when the hydroxyl group on one of the sugars reacts with the anomeric carbon on the second sugar. Maltose is hydrolyzed to two molecules of D- glucose by the intestinal enzyme maltase, which is specific for the α- (1, 4) glycosidic bond. Structure of Maltose Lactose Lactose is a disaccharide of β-D galactose and β-D- glucose which are linked by β-(1,4) glycosidic linkage. Lactose acts as a reducing substance since it has a free carbonyl group on the glucose. Since the anomeric carbons of both its component monosaccharide units are linked to each other. Structure of sucrose α-(1, 2) β-Glycosidic bond Polysaccharides Most of the carbohydrates found in nature occur in the form of high molecular polymers called polysaccharides. These are: • Homopolysaccharides that contain only one type of monosaccharide building blocks. Homopolysaccharides Example of Homopolysaccharides: Starch, glycogen, Cellulose and dextrins. It is especially abundant in tubers, such as potatoes and in seeds such as cereals. Starch consists of two polymeric units made of glucose called Amylose and Amylopectin but they differ in molecular architecture. Amylose is unbranched with 250 to 300 D-Glucose units linked by α-(1, 4) linkages Amylopectin consists of long branched glucose residue (units) with higher molecular weight. The branch points repeat about every 20 to 30 (1-4) linkages Glycogen - Glycogen is the main storage polysaccharide of animal cells (Animal starch). Cellulose is a linear unbranched homopolysaccharide of 10,000 or more D- glucose units connected by β-(1, 4) glycosidic bonds. Humans cannot use cellulose because they lack of enzyme (cellulase) to hydrolyze the β-( 1-4) linkages. Figure: Structure of Cellulose 30 Dextrins These are highly branched homopolymers of glucose units with α-(1, 6), α-(1, 4) and α-(1, 3) linkages. Since they do not easily go out of vascular compartment they are used for intravenous infusion as plasma volume expander in the treatment of hypovolumic shock. Hetero polysaccharides These are polysaccharides containing more than one type of sugar residues 1. They have the special ability to bind large amounts of water, there by producing the gel-like matrix that forms the basis of the body’s ground substance. Since they are negatively charged, for example, in bone, glycosaminoglycans attract and ++ + + tightly bind cattions like ca , they also take-up Na and K 3. An example of specialized ground substance is the synovial fluid, which serves as a lubricant in joints, and tendon sheaths. Heparin: • contains a repeating unit of D-glucuronic and D-gluconsamine, with sulfate groups on some of the hydroxyl and aminx-groups • It is an important anticoagualtn, prevents the clotting of blood by inhiginting the conversion of prothrombin to throbin.
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