1 Structure of Carbohydrates 大学动物营养学课件 英文版.pptVIP

Carbohydrates Jurgens and Bregendahl’s Animal Feeding and Nutrition pp. 8-27 Structure of Carbohydrates Sources of Carbohydrates Animal products Plants - major source Photosynthesis Nutrient Composition of an Adult Steer Water 54% Fat 26% Protein 15% Ash 4.6% Carbohydrate 1% little stored in the animal body Carbohydrates (CHO) C:H:O (1:2:1) The most abundant organic molecules in nature Sources Carbohydrates Carbohydrates are polyhydroxy aldehydes or ketones Classification Classified according to the number of sugar molecules: Most plants contain different types of carbohydrates than animals Monosaccharides (CnH2nOn) Classified by the number of carbon atoms: 3-C triose 4-C tetrose 5-C pentose 6-C hexose Monosaccharides Pentoses (5C) Xylose and arabinose Component in hemicellulose, glycoproteins Ribose Found in every living cell Found in compounds involved in metabolism: ATP/ADP Riboflavin DNA/RNA Monosaccharides Hexoses (6c) Glucose Component of starch, cellulose, and glycogen Major end-product of carbohydrate digestion in monogastrics Primary form of sugar used for energy Monosaccharides Hexoses (6c) Fructose 75% of sugars in honey Found in fruits and cane sugar Galactose Component of milk sugar (lactose) May be metabolized to glucose Mannose Found after hydrolysis of plant mannosans and gums; legumes Disaccharides Two monosaccharide molecules linked by a glycosidic (or acetal) bond Disaccharides Sucrose (glucose + fructose) Common table sugar Produced in leaves and stems of plants Found in sugar cane and sugar beets Disaccharides Cellulobiose (glucose + glucose) Beta 1-4 linkage in cellulose Does not exist freely in nature Oligo- and Poly-saccharides Oligosaccharide Chain of 3–10 sugar molecules Polysaccharide Chain of 10+ sugar molecules Polysaccharides Heteropolysaccharide - composed of two or more types of monosaccharides Homopolysaccharides - composed of one type of monosaccharide Starch Three forms of starch: 1. Amylose Apha 1-4 l