Starch & cellulose Flashcards
What type of reaction forms polysaccharides?
Condensation reactions
What are examples of polysaccharides?
Starch - storage molecule in plants
Cellulose - strength & support of cell wall in plants
What is the function of starch?
The main energy storage material in plants, it’s stored in the seeds of plants
What is starch broken down into?
Starch is broken down into glucose by plants when they need more energy. Starch can act as a source of food for humans and animals.
What other features does starch have?
Starch does not change the water potential in a cell because it’s insoluble in water. It is made up of amylopectin and amylose, which are both alpha-glucose polysaccharides.
What is amylopectin?
Amylopectin is a highly branched chain of alpha-glucose monomers
What is amylose?
Amylose is a linear chain of alpha-glucose monomers. Because of the way the monomers are joined, the glucose chains have a helical structure.
How do amylose & amylopectin contribute to starch’s features?
The amylose strands can pack closely together, making this form of starch particularly good for storage.
The branched structure of amylopectin means that enzymes can easily access the glycosidic bonds and so the glucose molecules can be quickly released when needed.
How do you test for starch?
Step 1: Place a small sample into the dimple of a spotting tile or to a boiling tube.
Step 2: Add a few drops of iodine and observe any colour change.
If starch is present, the solution will change colour from orange → blue-black.
What is the structure of cellulose?
Cellulose is a long chain of beta-glucose. Beta-glucose molecules are linked by glycosidic bonds to form linear cellulose chains that are unbranched.
What are microfibrils?
Strong fibres that are made of many cellulose chains that are held together by hydrogen bonds
What is the function of cellulose?
The cell walls of plant cells are mostly made of cellulose. These cell walls offer structural support because of the strength of the microfibril fibres that they are made of.
