Polysaccarides
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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

Polysaccarides

Starch and Glycogen


Learning outcomes

Learning Outcomes


Starch

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)


Starch1

Starch

  • A mixture of two compounds

    - AMYLOSE

    - AMYLOPECTIN


How is amylose made

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


Condensation reaction

C

C

C

C

O

O

C

C

C

C

C

C

C

C

Condensation reaction

OHH

OHH


Condensation reaction1

C

C

C

C

O

O

C

C

C

C

C

C

C

C

Condensation reaction

OH

OH


Condensation reaction2

C

C

C

C

O

O

C

C

C

C

C

C

C

C

Condensation reaction

O

H2O


Condensation reaction3

C

C

C

C

O

O

C

C

C

C

C

C

C

C

Condensation reaction

4

1

O

disaccharide

a1,4glycosidic bond


How is amylose made1

How is amylose made …

  • The same condensation reaction is repeated over and over again to join thousands of glucose molecules together

    to make

    AMYLOSE


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

STRUCTURE OF AMYLOSE


Amylopectin

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


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

Starch Insoluble store of glucose in plantsformed from two glucose polymers:


Glycogen

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


Structure of glycogen

Structure of Glycogen


Structure linked to function

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


Questions

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?


Answers

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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