Lecture 14 15 1 Introduction Carbohydrates Subunit Interactions

Lecture 14. 15. 1. Introduction Carbohydrates Subunit Interactions to Biochemistry and Quaternary Structure Carbohydrates n most abundant organic molecules in nature 1 11

IMPORTANCE n n Photosynthesis stores energy in carbohydrates; Carbohydrates are the metabolic precursors of all other biomolecules; Important component of cell structures; Important function in cell-cell recognition;

Carbohydrate Classes n Monosaccharide n n n Simple sugars, can not be broken down further; general formula (CH 2 O)n Examples 3

Alpha vs Beta glucose

n Can be n Aldoses n n Contain aldehyde Ketoses n Contain ketones

n n Disaccharide - two sugars formed by dehydration synthesis

n glucose + fructose sucrose + water table sugar n glucose +galactose + water milk sugar n glucose + glucose maltose + water malt sugar

Lecture 15. Carbohydrates 8 Carbohydrate Classes n Disaccharides n n Simplest oligosaccharides; Contain two monosaccharides linked by a glycosidic bond;

Oligiosaccharide n short chain 3 -10 monomers long n Identification on cells

Carbohydrate Classes n Polysaccharides n Polymers of monosaccharides

Lecture 15. Carbohydrates Polysacchrides n n n Starch and glycogen are storage molecules; Chitin and cellulose are structural molecules; Cell surface polysaccharides are recognition molecules. 11

Lecture 15. Carbohydrates Polysacchrides n Glucose is the monosaccharides of the following polysacchrides with different linkages and banches n n a(1, 4), starch (more branch) a(1, 4), glycogen (less branch) b(1, 4), cellulose (cell walls of all plants) b(1, 4), Chitin similar to cellulose, but C 2 -OH is replaced by –NHCOCH 3 (found in exoskeletons of crustaceans, insects, spiders) 12

Carbohydrates n n n Polysaccharide - glycogen many glucose units in a branching pattern liver and skeletal muscle are good sources hormone insulin stimulates glycogen production (glycogenesis) hormone glucagon stimulates glycogen breakdown (glycogenolysis) glycogen is found in animal cells as an inclusion

Carbohydrates n n n Starches are complex carbohydrates, often two polysaccharide chains plants make starches, including the indigestible cellulose examples - wheat, rice, corn, potato, cassava, rye, barley