1. Polysaccarides
Starch and Glycogen

2. Learning Outcomes
Describe the formation and breakage of glycosidic bonds in the synthesis and hydrolysis of a polysaccharide.
Describe the structure of starch
Describe the structure of glycogen.
Explain how the structures relate to the functions
of starch and glycogen

4. Starch The most abundant storage chemical in plants
The single largest provider of energy for the world’s population
Properties
Compact
Insoluble
Readily accessible when needed(quickly hydrolysed)

5. Starch
A mixture of two compounds
- AMYLOSE
- AMYLOPECTIN

6. Condensation reaction
How is Amylose made?
2 α-glucose molecules bond together
Via a
Condensation reaction
to form a
1,4-Glycosidic bond
to make a
Disaccharide
called
Maltose

7. Condensation reaction
OHH
OHH

8. Condensation reactionOH OH

9. Condensation reaction
H2O

10. Condensation reaction1 4 O
disaccharide
a 1,4 glycosidic bond

11. How is amylose made …
The same condensation reaction is repeated over and over again to join thousands of glucose molecules together
to make
AMYLOSE

12. STRUCTURE OF AMYLOSE COMPACT COIL WHY?
BONDS ARE BROUGHT TOGETHER AT A SLIGHT ANGLE when repeated many times, a spiral molecule is made
Inward pointing H bonds stabilise the structure

13. AMYLOPECTIN
Branched molecule – 1,6 glycosic bonds every so often cause side chains
Molecule is a tightly packed and brush-like
Can be broken down more quickly than amylose

14. Starch Insoluble store of glucose in plants formed from two glucose polymers:
Amylose
-glucose
1,4 glycosidic bonds
Spiral structure
Amylopectin
-glucose
1,4 and some 1,6 glycosidic bonds
Branched structure

15. GLYCOGEN Major storage carbohydrate in animals
Large molecule made of α-glucose units
Can be broken down to release the glucose
Like amylopectin in structure has many more branches though
More compact than starch
Stored in liver and muscle cells

16. Structure of Glycogen

18. Structure linked to function
Both glycogen and starch….
Are insoluble – will not bring about large movement of water by osmosis
Compact – lots stored in a small space
Easily broken down/hydrolysed at the ‘ends’ of the chains – to release glucose for respiration

19. Questions
Glycogen is more branched than amylopectin. Explain how this difference is important to animals
Why are glycogen and starch storage molecules whereas glucose is an energy source?

20. Answers
Animals have a higher /rapid demand for energy to support movement of muscles. Increased branching in glycogen means more ‘ends’ to release more glucose for respiration
Glycogen and starch must be broken down first before the glucose can be respired. Glucose can be respired immediately.