1. Carbohydrates

2. What are carbohydrates? Starter: Write down as many things as you can remember about carbohydrates… … or glucose in particular

3. What are they? Organic compounds which comprise of only C, H and O Carbo-Hydr-ate

4. Types of Carbohydrate Monosaccharides Disaccharides Polysaccharides

5. Monosaccharides Simplest – ‘Single sugars’ Same no. of C as O atoms e.g. Glucose is C 6 H 12 O 6 Have the general formula (CH 2 O) n Where n is any number between 3 and 7 White crystalline solids Dissolve in water to form sweet tasting solutions

6. The structure of glucose α-glucose You only need to be able to draw α-glucose in its simplified form….

7. β-glucose The structure of glucose α-glucose and β-glucose are ISOMERS

8. Monosaccharides form Disaccharides + H2OH2O Maltose

9. The bond formed is a glycosidic bond A condensation reaction occurs to join the 2 monosaccharides Monosaccharides form Disaccharides α 1-4 glycosidic bonds

10. Disaccharides hydrolyse to form Monosaccharides α-glucose H2OH2O

11. Disaccharides form Polysaccharides Starch

12. The α-helical structure of starch makes it good for storage (it’s compact!) Starch is insoluble due to its structure It is therefore the main plant storage sugar

13. Starch Made of two alpha glucose polymer Amylose Spiral structure with 1,4 glycosidic bond Amylopectin Branched structure with 1,4 and some 1,6 glycosidic bond

14. Glycogen Insoluble compact store of glucose in animal Alpha glucose with 1,4 and 1,6glycosidic bond Branched structure

15. Cellulose Polymer of β-glucose Each monomer is inverted. Has consequences for its properties

16. Cellulose Forms chains which run parallel with hydrogen bonds between the chains to form microfibrils Microfibrils are strong Being fibrous, cellulose is structurally important in plant cell walls

17. Glucose is not the only monosaccharide... Fructose: Glucose and fructose combine to form sucrose (a disaccharide)

18. Glucose is not the only monosaccharide... Galactose Glucose Glucose and galactose combine to form Lactose

19. Summary α-glucose + α-glucose = maltose The polymer of α-glucose is starch The polymer of β-glucose is cellulose Glucose + fructose = sucrose Glucose + galactose = lactose

20. Carbohydrates Questions answer in full sentences please 1.What is the function of the following carbohydrates in living things: glycogen, starch, cellulose, sucrose? 2.What are the 2 structural isomers of glucose called? Describe in words why they are different. Draw the 2 structures.

21. Biochemical Test for a Monosaccharide

22. All monosaccharides and some disaccharides are Reducing Sugars i.e. They readily reduce other chemicals when in solution We test for reducing sugars using the Benedict’s Test

23. Benedicts Test 2cm³ of food sample (in liquid form) 2cm³ of Benedict’s Reagent Heat mixture in gentle boiling water bath for 5mins Conc. of reducing sugarColour of solution & precipitate NoneStays blue Very LowGreen LowYellow MediumBrown/orange HighBrick red

24. In order to detect a reducing sugar, it must first be ___________into its monosaccharide components: – First test with Benedict’s reagent – If no colour change: Add 2cm³ of food sample to 2cm³ of dilute HCl Place in gently boiling water bath for 5 mins Slowly add some sodium hydrogen carbonate solution until neutralized Re-test using Benedict’s reagent hydrolysed

25. If I am the Answer, what is the Question? Monosaccharide Disaccharide Polysaccharide Glycosidic bond Condensation reaction Hydrolysis reaction Isomer Carbohydrate ( CH 2 O ) n Benedict’s Test Maltose Starch