CARBOHYDRATES

Learning Outcomes: B4 – analyse the structure and function of biological molecules in living systems - carbohydrates Know formulas, chemical structure List functions Differentiate between monosaccharaides, disaccharides and polysaccharides Compare structure of cellulose, starch and glycogen Explain dehydration synthesis and hydrolysis

Elements Carbohydrates contain C, H, and O in a ratio of approximately 1:2:1 2:1 ratio of H to O is the same is in H2O Contain repetitions of H-C-OH

Monomers Monosaccharides (Simple carbohydrates, or sugars) Common monosaccharides have 5 or 6 carbons, usually arranged in a ring

Hexoses are 6-carbon monosaccharides Ex. Glucose, fructose, and galactose All have the formula C6H12O6 Differ in arrangement of atoms Draw glucose. See p.32 for other ways to draw.

3 Ways to draw glucose

Another view:

Structural formula for glucose: Each corner is a carbon atom

Pentoses are 5-Carbon monosaccharides Ex. Ribose

Polymers Monosaccharides combine in chains to form polymers Two monosaccharides combined = a disaccharide Several monosaccharides combined = a polysaccharide

Disaccharides (2 monosaccharides) Ex. glucose + glucose  maltose Glucose + fructose  sucrose Glucose + galactose  lactose Draw as on pagae 32

Sucralose … Tastes like sugar, looks like sugar, but it’s not!

Polysaccharides (complex carbohydrates) Long, branched or unbranched chains of monosaccharides (up to 4000!) Common examples: starch, glycogen, cellulose Differ in orientation of bonds and degree of branching

Starch Draw as on page 33

Glycogen Draw as on p 33

Cellulose Draw as on p 33

Functions of Carbohydrates Glucose and other monosaccharides are used in cellular respiration, to provide energy for cellular functions in all living organisms Glycogen is used for energy storage in animals (found mainly in muscles and liver)

Starch is used for energy storage in plants (digested by animals to provide energy from food)

Cellulose provides structure in plant cell walls

Condensation Synthesis and Hydrolysis Monosaccharides combine to form polymers by the process of condensation synthesis, or dehydration synthesis A water molecule is given off for each bond that forms Draw pictures on overhead step by step

One molecule of H2O is added for each bond that is broken Polysaccharides are broken down into monosaccharides by the process of hydrolysis One molecule of H2O is added for each bond that is broken Draw pictures on overhead step by step