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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

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 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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