[理学]chapter 19 carbohydrates and nucleic acids 2 核酸和碳水化合物.ppt

Chapter 19 Chapter 19 Carbohydrates Carbohydrates Synthesized by plants using sunlight to convert CO2 and H2O to glucose and O2. Polymers include starch and cellulose. Starch is storage unit for solar energy. Most sugars have formula Cn(H2O)n, “hydrate of carbon.” = Chlorophyll molecules in green plants capture the light energy used in photosynthesis. Classification of Carbohydrates Monosaccharides or simple sugars polyhydroxyaldehydes or aldoses polyhydroxyketones or ketoses Disaccharides can be hydrolyzed to two monosaccharides. Polysaccharides hydrolyze to many monosaccharide units. E.g., starch and cellulose have 1000 glucose units. = the term carbohydrate, saccharide, and sugar are ofetn used interchangeably. Saccharide comes from the word for sugar in sevsral early languages.(sarkara in Sanskrit, sakcharon in Greek, and saccharum in Latin). monosaccharides A monosaccharide can be a polyhydroxy aldehyde or ketone. Polyhydroxy aldehydes are called aldoses, polyhydroxy ketones are called ketoses. Monosaccharides are also classified according to the number of carbons they contain, monosaccharides with three carbons are trioses, with 4 carbons are tetroses, with 5 carbons are pentoses,with 6 carbons are hexoses. so, such as D-glucose is an aldohexoses PROBLEM 1 Classify the following monosaccharides: The D and L notation Emil fischer and his colleagues studied carbohydrates in the late nineteenth century, when techniques for determining the configurations of compounds were not avaiable.Fischer arbitrarily assigned the configuration shown above on the left to the dextro- rotatory isomer of glyceraldehyde that we call D-glyce- raldehyde, and the enantiomer is L-glyceraldehyde. PROBLEM