Polysaccharide Structure: Starch and Cellulose Flashcards
1
Q
What is a polysaccharide?
A
- A carbohydrate that contains many sugar units
- Two+ monosaccharides joined together
- They are, generally, insoluble, unlike monosaccharides and disaccharides
2
Q
Give examples of a polysaccharide.
A
- Glycogen: storage molecule in animals, 1-6 and 1-4 glycosidic bonds (1-4 more common than 1-6). Have 1-4 bonds with 1-6 bonds spiralling and branching off
- Starch: storage molecules in plants, 1-6 and 1-4 glycosidic bonds (1-4 more common), 1-6 bonds more frequent in glycogen molecules than starch
3
Q
Give examples of starch.
A
- Amylose
- Amylopectin
4
Q
Describe the structure of amylose.
A
- Only 1-4 glycosidic bonds
- 20-30% of starch inside plant is in this form
- Compact so it is good for storage
5
Q
Describe the structure of amylopectin.
A
- Contains both 1-4 and 1-6 glycosidic bonds
- Similar to glycogen, only difference is the frequency residue
- 70-80% of starch is stored inside plant in this form.
- Side branches allow enzymes to get at glycosidic bonds easily meaning glucose can be released quickly
6
Q
What is a disaccharide?
A
When two monosaccharides join together in a condensation reaction.
7
Q
Why is the conversion of glucose into starch beneficial for plants?
A
Starch is insoluble in water so it doesn’t cause water to enter cells by osmosis. This prevents them from swelling, making starch good for storing energy.
8
Q
Why is the conversion of glucose into glycogen beneficial for humans?
A
Glycogen is insoluble in water meaning cells will not swell as water is not drawn into them via osmosis.
9
Q
Describe the structure of glycogen.
A
- Has 1-4 and 1-6 glycosidic bonds
- Lots of side branches (more than amylopectin) so stored glucose can be released quickly which is important for energy release in animals.
- Compact so good for storage
- Large molecule so it can store lots of energy
