Polysaccharides Flashcards
How are polysaccharides formed
Formed by many monosaccharides linked by glycosidic bonds.
Three types of polysaccharides
- starch
- glycogen
- cellulose
Properties of polysaccharides
- Do not taste sweet
- Insoluble in water
- Non-reducing sugars
- Function as storage or structural molecules
What are starches
- Long branched chains of alpha glucose joined together by glycosidic bonds as a result of condensation reaction
- Starch is stored in the starch grains found in plants
Explanation of how structure leads to function
- LARGE so can’t cross the cell membrane and leave the cell
- INSOLUBLE therefore osomotically inactive
- HELICAL shape can compact to fill a lot of glucose in a small space
- BRANCHED structure increases surface area for rapid hydrolysis back to glucose
Describe the iodine test for starch
- Add 2-3 drops of potassium iodide sugar
- If starch is PRESENT, blue/black colour appears
- If starch is ABSENT, iodine solution will remain orange/yellow
Hydrolysis of starch
- Starch is hydrolysed by an enzyme amylase to produce the disaccharide maltose.
-Starch + water ————–> maltose
(amylase)
How is glycogen formed?
Condensation reaction of alpha glucose
Where is glycogen found?
Liver and muscle cells
Function of glycogen?
Store of glucose
Explanation of how structure leads to function
- High branched structure increases surface area for rapid hydrolysis back to glucose.
- Insoluble therefore osmotically inactive
Where is cellulose found?
Cell wall of plants
Function of cellulose
Provides rigidity and shape to cell which prevents it from bursting (osmolysis)
Shape of cellulose
Long straight chains of beta glucose molecules joined together by a glycosidic bond in a condensation reaction.
Explanation of how structure leads to function
- Long straight chains held parallel by many hydrogen bonds to form microfibrils. This provides collective strength
- Insoluble therefore osmotically inactive
