Carbohydrates Carbohydrate: a ________________ or ______________, or a substance that gives these compounds on hydrolysis Monosaccharide: a carbohydrate that cannot be _____________ to a simpler carbohydrate –they have the general formula C n H 2n O n, where n varies from 3 to 8 –aldose: a monosaccharide containing an aldehyde group –ketose: a monosaccharide containing a ketone group

Fig 19.UN, p.472

d:\gob.exe Go to GOB slide 2 – classifying carbohydrates

Monosaccharides There are only two trioses –often aldo- and keto- are omitted and these compounds are referred to simply as trioses; although this designation does not tell the nature of the carbonyl group, it at least tells the number of carbons

Monosaccharides Glyceraldehyde contains a stereocenter and exists as a pair of enantiomers

Fig. 19.1, p.467

Fischer Projections Fischer projection: a two dimensional representation for showing the configuration of tetrahedral __________________ –____________ lines represent bonds projecting forward –vertical lines represent bonds projecting to the ______

D,L Monosaccharides In 1891, Emil Fischer made the arbitrary assignments of D- and L- to the enantiomers of glyceraldehyde

D,L Monosaccharides According to the conventions proposed by Fischer –D-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the - OH on its ___________ carbon on the right –L-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the - OH on its penultimate carbon on the ______

Following are the two most common D- aldotetroses and D-aldopentoses D,L Monosaccharides

and the three common D-aldohexoses. Note that one of these is an amino sugar

Table 19.1, p.468

Table 19.2, p.469

Cyclic Structure Monosaccharides have hydroxyl and carbonyl groups in the same molecule and exist almost entirely as five- and six- membered cyclic ______________ –__________ carbon: the new stereocenter resulting from cyclic hemiacetal formation –_______ : carbohydrates that differ in configuation at their anomeric carbons

Fig 19.UN, p.471

Fig 19.2, p.472

Haworth Projections Haworth projections –five- and six-membered hemiacetals are represented as planar ________ or ________, as the case may be, viewed through the edge –most commonly written with the ________ carbon on the right and the hemiacetal oxygen to the back right –the designation  means that -OH on the anomeric carbon is cis to the terminal -CH 2 OH; ___ means that it is trans

d:\GOB.exe Go to GOB slide 3

Mutarotation Mutarotation: the change in specific rotation that occurs when an  or  form of a carbohydrate is converted to an equilibrium mixture of the two

Mutarotation: the change in specific rotation that occurs when an a or b form of a carbohydrate is converted to an equilibrium mixture of the two

Reduction to Alditols The carbonyl group of a monosaccharide can be reduced to an hydroxyl group by a variety of reducing agents, including NaBH 4 and H 2 /M

Oxidation to Aldonic Acids Oxidation of the -CHO group of an aldose to a -CO 2 H group can also be carried out using Tollens’, Benedict’s, or Fehling’s solutions

Oxidation to Aldonic Acids 2-Ketoses are also oxidized by these reagents because, under the conditions of the oxidation, 2-ketoses equilibrate with isomeric _________

Fig 19.UNc, p.478

Glucose Assay The analytical procedure most often performed in the clinical chemistry laboratory is the determination of glucose in blood, urine, or other biological fluid –this need stems from the high incidence of diabetes in the population

Glucose Assay The glucose oxidase method is completely specific for D-glucose

Glucose Assay –the enzyme glucose oxidase is specific for  -D-glucose –molecular oxygen, O 2, used in this reaction is reduced to hydrogen peroxide H 2 O 2 –the concentration of H 2 O 2 is determined experimentally, and is proportional to the concentration of glucose in the sample –in one procedure, hydrogen peroxide is used to oxidize o-toluidine to a colored product, whose concentration is determined spectrophotometrically

Fig 19.UNa, p.480

Problem 19.40, p.491

Glycosides _________ bond: the bond from the anomeric carbon of the glycoside to an -OR group __________ are named by listing the name of the alkyl or aryl group attached to oxygen followed by the name of the carbohydrate with the ending -e replaced by -ide –methyl  -D-glucopyranoside –methyl  -D-ribofuranoside

Formation of Glycosides Glycoside: a carbohydrate in which the - OH of the anomeric carbon is replaced by - OR Methyl  -D-glucopyranoside (methyl  -D- glucoside)

Fig 19.UNa, p.475Fig 19.UNb, p.476

d:\GOB.exe Go to GOB slide 5

The –OR group of the glycoside may be another monosaccharide – the resulting glycoside is then a disaccharide Examples of important disaccharides follow:

Maltose From malt, the juice of sprouted barley and other cereal grains

beta-maltose

Lactose The principle sugar present in milk –about 5% - 8% in human milk, 4% - 5% in cow’s milk

lactose

Sucrose Table sugar, obtained from the juice of sugar cane and sugar beet

Cellulose Cellulose is a linear polymer of D-glucose units joined by  -1,4-glycoside bonds –it has an average molecular weight of 400,000, corresponding to approximately 2800 D- glucose units per molecule

Starch Starch is used for energy storage in plants –it can be separated into two fractions; amylose and amylopectin. Each on complete hydrolysis gives only D-glucose –amylose is composed of continuous, unbranched chains of up to 4000 D-glucose units joined by  -1,4- glycoside bonds –amylopectin is a highly branched polymer of D- glucose. Chains consist of units of D-glucose joined by  -1,4-glycoside bonds and branches created by  -1,6-glycoside bonds

Glycogen Glycogen is the reserve carbohydrate for animals Like amylopectin, glycogen is a nonlinear polymer of D-glucose units joined by  -1,4- and  -1,6-glycoside bonds bonds The total amount of glycogen in the body of a well-nourished adult is about 350 g (about 3/4 of a pound) divided almost equally between liver and muscle

Fig 19.UN, p.487

Heparin is made of sulfonated polysaccharide chains

Fig 19.UN, p.487

Problem 19.67, p.493

Blood Group Substances Membranes of animal plasma cells have large numbers of relatively small carbohydrates bound to them These membrane-bound carbohydrates are part of the mechanism by which cell types recognize each other; they act as antigenic determinants Among the first discovered of these antigenic determinants are the blood group substances