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Polysaccarides

Polysaccarides. Starch and Glycogen. Learning Outcomes. 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). Starch.

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Polysaccarides

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  1. Polysaccarides Starch and Glycogen

  2. Learning Outcomes

  3. 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)

  4. Starch • A mixture of two compounds - AMYLOSE - AMYLOPECTIN

  5. 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

  6. C C C C O O C C C C C C C C Condensation reaction OHH OHH

  7. C C C C O O C C C C C C C C Condensation reaction OH OH

  8. C C C C O O C C C C C C C C Condensation reaction O H2O

  9. C C C C O O C C C C C C C C Condensation reaction 4 1 O disaccharide a1,4glycosidic bond

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

  11. 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 STRUCTURE OF AMYLOSE

  12. 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

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

  14. 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

  15. Structure of Glycogen

  16. 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

  17. 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?

  18. 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.

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