Polysaccharides Flashcards
When is a polysaccharide formed?
When more than 2 monosaccharides are joined together by condensation reactions
How can polysaccharides be broken down into their constituent monosaccharides?
By hydrolysis reactions
Where do cells get energy from?
Glucose
What do plants store excess glucose as?
Starch
What 2 polysaccharides of alpha-glucose make up starch?
Amylose
Amylopectin
What is amylose?
Long, unbranched chain of alpha-glucose
Describe the structure of amylose?
Why is it good for storage?
Angles of glycosidic bonds give it a coiled structure, almost like a cylinder
Makes it compact, so it’s good for storage because you can fit more into a small space
What is amylopectin?
Long, branched chain of alpha-glucose
Describe the structure of amylopectin?
What does this mean for the releasing of glucose?
Side branches allow enzymes that break down the molecules to get at the glycosidic bonds easily
This means that glucose can be released quickly
Why is starch good for storage?
Insoluble in water and doesn’t affect water potential
So doesn’t cause water to enter cells by osmosis
Which would make them swell
Where do animal cells get energy from?
Glucose
What do animals store excess glucose as?
Glycogen
What is the structure of glycogen like?
Similar to amylopectin but has more side branches
What do more branches in glycogen mean?
Stored glucose can be released quickly
This is important for energy release in animals
Why is glycogen good for storage?
It is a very compact molecule
What is cellulose made of?
Long, unbranched chains of beta-glucose
What happens when beta-glucose molecules bond?
They form straight cellulose chains
What are cellulose chains linked together by?
What does this form?
Hydrogen bonds
Strong fibres called microfibrils
What do the strong fibres mean for cellulose?
Example of what cellulose is used in?
Provides structural support for cells
Plant cell walls
What test is used to test for starch?
Iodine test
How do you carry out the iodine test?
Add iodine dissolved in potassium iodide solution to the test sample
What does a dark, blue-black colour indicate in the iodine test?
Starch is present
What does a browny-orange colour indicate in the iodine test?
No starch is present
