Sugar Notes

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  • Created by: sarah109
  • Created on: 16-09-16 13:16
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IodinePotassium Test Presence of Starch
Iodine solution reacts with starch
Results in a colour change from orangebrown to blueblack
Qualitative test accurate concentration cannot be determined
The depth of blueblack gives an idea of relative concentration
Like Benedict's, it is qualitative
IF STARCH IS PRESENT IN THE SOLUTION BEING TESTED:
The solution will change from orangebrown to blueblack
IF STARCH IS NOT PRESENT IN THE SOLUTION BEING TESTED:
The solution will remain orangebrown and not change colour
Disaccharides and Polysaccharides
FORMATION OF DISACCHARIDES
Two monosaccharides joined together by a glycosidic bond
Happens in a condensation reaction (elimination of water)
14 glycosidic bonds are formed because the bond is between carbon no. 1 on one monosaccharide
and no. 4 on the other monosaccharide
The disaccharide molecule is straight and not twisted, and so the glycosidic bond formed is
an alpha1, 4 glycosidic bond
EXAMPLES OF DISACCHARIDES
MALTOSE glucose + glucose in germinating seeds
SUCROSE glucose + fructose transport in phloem of flowering plants
LACTOSE glucose + galactose found in mammalian milk
POLYSACCHARIDES
Large, complex polymers
Monosaccharides are their monomers
Linked by glycosidic bonds
Polysaccharides Starch
WHY IS GLUCOSE CONVERTED TO STARCH?
Glucose is soluble in water, and so consequently would draw water into the cell by osmosis
Starch is insoluble, can't diffuse out of cell, compact molecule, lots of energy in CH and CC bonds
STARCH
Main glucose storage in plants. Found in high concentration in seeds and storage organs
Made of alphaglucose molecules bonded in two different ways, forming AMYLOSE and
AMYLOPECTIN
AMYLOSE

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Liner, unbranched molecules
Consists of alpha1, 4 glycosidic bonds
Coils into an alphahelix
AMYLASE
Chains of glucose monomers joined with alpha 1,4 glycosidic bonds
Crosslinked with alpha1, 6 glycosidic bonds.…read more

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Building blocks for larger molecules (i.e. disaccharides and polysaccharides)
Intermediates in reactions
Constituents of nucleotides (e.g.…read more

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Gives an accurate measurement of blood glucose…read more

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