1. Enzymes and the digestive system
2.3 Carbohydrates - Polysaccharides
11/13/2018

2. Settler Activity: Unscramble these anagrams!
ASHOPCLAYCRIED
ADISCHIDECAR
MADESOONCHARDICE
CHARTS
SOGCLUE
LIDCIGCOSY DNOB
DENTSOCATION CREATINO
HISSYLODRY CREATINO
Polysaccharide
Disaccharide
Monosaccharide
Starch
Glucose
Glycosidic bond
Condensation reaction
Hydrolysis reaction
11/13/2018

3. Learning Objectives All students should be able to...
Describe how α-glucose molecules link together to form starch?
Give examples of storage and structural polysaccharides.
Describe and carry out the test for starch?
Specification reference: 3.1.2
11/13/2018

4. Success Criteria
I can classify carbohydrates as monosaccharides, disaccharides and polysaccharides.
I can name two storage polysaccharides.
I can name a structural polysaccharide.
I can describe the stages of the starch test.
I can carry out the starch test.
11/13/2018

5. Starter Activity: Can you classify these carbohydrates?
Monosaccharide
Disaccharide
Polysaccharide
Galactose
Glycogen
Starch
Sucrose
Lactose
Glucose
Maltose
Fructose
Cellulose
11/13/2018

6. Polysaccharides
Polysaccharides are polymers, formed by combining together many monosaccharide molecules.
The monosaccharides are joined by glycosidic bonds that were formed by condensation reactions.
As polysaccharides are very large molecules, they are insoluble.
This feature makes them suitable for storage.
When they are hydrolysed, polysaccharides break down into disaccharides or monosaccharides.
Some polysaccharides, such as cellulose, are not used for storage but give structural support to plant cells.
Starch is a polysaccharide that is found in many parts of plants in the form of granules or grains, e.g. Starch grains in chloroplasts. It is formed by the linking of between 200 and 100,000 α-glucose molecules by glycosidic bonds in a series of condensation reactions.
11/13/2018

7. Test for starch
Starch is easily detectable by its ability to change the colour of the iodine in potassium iodide solution from yellow to blue-black. The test is carried out at room temperature.
Place 2cm3 of the sample being tested into a test tube (or add two drops of the sample into a depression on a spotting tile).
Add two drops of iodine solution and shake or stir.
The presence of starch is indicated by a blue-black coloration.
11/13/2018

8. Plenary Questions Name 3 polysaccharides.
Which polysaccharide gives structural support to plant cells?
Which polysaccharide is used for storage of energy in plants?
Which polysaccharide is used for storage of energy in animals?
What feature of polysaccharides makes them suitable for storage?
In what form do you find starch?
Describe the test for starch?
How is starch formed?
11/13/2018

9. Plenary Questions Cellulose, Glycogen and Starch Cellulose Starch
Very large molecules, therefore they are insoluble, making them suitable for storage.
Small granules or grains
Add 2 drops of iodine solution to test solution. If starch is present it turns the iodine a blue-black colour.
Starch is formed by the linking of between 200 and α-glucose molecules by glycosidic bonds in a series of condensation reactions.
11/13/2018

10. Learning Objectives All students should be able to...
Describe how α-glucose molecules link together to form starch?
Give examples of storage and structural polysaccharides.
Describe and carry out the test for starch?
Specification reference: 3.1.2
11/13/2018