Polysaccharides Flashcards
1
Q
What is starch? What is it made of? Composition % ? What properties ?
A
- 2 different polysaccharides make up starch
- Amylopectin (70/90%)
- Amylose (10-30%)
Amylopectin : α glucose, 1,4 and 1,6 glycosidic bonds, making it BRANCHED
Amylose : α glucose, 1,4 glycosidic bonds, HELIX SHAPED so COMPACT and so more resistant to digestion
2
Q
What is glycogen? What is its composition? Structure?
A
- α glucose
- 1,4 and 1,6 glycosidic bond
- Branched
- More branches than amylopectin
3
Q
What is cellulose? Composition? Structure?
A
- Long chains of β glucose with 1,4 glycosidic bonds.
- Inversion of β glucose means lots of hydrogen bonds form between long chains giving cellulose its strength
4
Q
Function and structural benefits of starch
A
- Storage molecule in plants
- Stored as granules in plastids (membrane bound organelles in plant cells with particular functions, like amyloplasts which store starch grains)
- Amylopectin is folded into a helix, so compact and harder to digest
- Branches with lots of terminal glucose molecules which are easily hydrolysed for respiration
- Insoluble so no osmotic effect on cells
- Compact so lots can be stored in a small space
5
Q
Function and structural benefits of glycogen
A
- Storage polysaccharide in animals and fungi
- Very highly branched, compact, more stored in a small space
- No osmotic effect, not soluble
- Lots of glucose ends to be readily hydrolysed for respiration
6
Q
Function and structural benefits of cellulose
A
- Structural component of cell walls
- Lots of hydrogen bonds due to glucose being inverted each molecule, giving cellulose its strength
- High tensile strength lets it be stretched without breaking, so cell walls can withstand turgor pressure
- Cellulose fibres and lignin forms matrix which increases strength of cell walls, supporting the plant
- Freely permeable so water and solutes can enter and leave cell
- Few animals have cellulase to hydrolyse cellulose so it is indigestible
