Carbohydrates o, p

Learning Objectives (o) describe the basic structure of carbohydrates, with reference to monosaccharides, disaccharides and polysaccharides; (p) describe, with the aid of diagrams, the structure of the ring form of alpha glucose;

Introducing carbohydrates Carbohydrates are a group of substances used as both energy sources and structural materials in organisms. All carbohydrates contain carbon, hydrogen and oxygen, with the general formula: C x (H 2 O) y. There are three main groups of carbohydrates: monosaccharides – these are simple sugars, with the general formula (CH 2 0) n, where n can be 3–7 disaccharides – these are ‘double sugars’, formed from two monosaccharides polysaccharides – these are large molecules formed from many monosaccharides.

Glucose The structure of glucose can be represented in different ways: Glucose is an abundant and very important monosaccharide. It contains six carbon atoms so it is a hexose sugar. Its general formula is C 6 H 12 O 6. Glucose is the major energy source for most cells. It is highly soluble and is the main form in which carbohydrates are transported around the body of animals. straight chain ring ring (simplified)

Alpha and beta glucose Glucose exists in different forms called structural isomers. Two common isomers are alpha glucose and beta glucose. alpha glucose beta glucose The only difference between these two isomers is the position of the –OH group attached to carbon 1. In alpha glucose it is below the carbon and in beta glucose it is above the carbon This minor structural difference has a major effect on the biological roles of alpha and beta glucose.

The formation of disaccharides

Task Read instructions carefully

Method 1.Label 7 test tubes: 2.0%, 1.0%, 0.5%, 0.05%, 0.02% and 0.01%. 2.Add 3 cm³ of each glucose solution to the appropriate test tube. 3.Add 5 cm³ of Benedict’s solution 4.Place the test tubes in a boiling water bath(use a beaker and boiling water from the kettle) for 8 minutes, then leave them to cool in air. 5.Prepare the food sample (use pestle and mortar if necessary and then dissolve it in 5.0 cm³ water). 6.Filter the solution. Keep the filtrate 7.Use Clinistick to test for sugar in the sample. 8.Label test tube with the food sample. 9.Pipette 5.0 cm³ of Benedict’s reagent into a test tube. 10.Add 3 cm³ of the food sample solution to be tested. Heat in a boiling water bath for 8 minutes. Then leave to cool. 11.Compare the colour produced with the colour standards.

Results table Now draw results table

Homework outline how the concentration of glucose is measured in human blood. Include the normal values for before and after meals and at bed time. Due next Friday