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Preview of Carbohydrates

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Unit 1 ­ Biology and disease
Biological Molecules
Organic Molecules
Organic molecules always contain carbon
EG: Glucose - CH0, Methane - CH, Carbon Dioxide, CO
Carbon can bond to itself as well as other atoms in:
1. Straight Chains
2. Branched Chains (amino acids)

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3.…read more

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Triple bonds are rare but can form between two carbon atoms or a carbon atom and a
nitrogen atom
Many organic compounds are polymers made up of monomers
For every covalent bond made, a unit of water is lost, therefore when you combine
monomers it is called a condensation reaction.
To make a polymer you need LOTS of condensation reactions, therefore it is called
condensation polymerisation.…read more

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EG a dimer is broken down into two monomers by adding one unit of water to break its
one bond)
Also called saccharides…read more

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They contain carbon, hydrogen and oxygen.…read more

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EG glyceraldehyde
(CHO)n where n = 5 i.e. CHO
Examples include ribose and deoxyribose
Ribose is an important constituent of RNA and can exist as a straight chain or as a ring
(structural isomers)
(CHO)n where n = 6 i.e.…read more

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Examples include glucose, fructose and galactose which are all isomers of each other
Glucose can exist as two forms, alpha ( ) glucose or beta ( ) glucose.…read more

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Method: (explanations)
1. Put 5cm³ of the solution into a boiling tube
2. Add 5cm3 of Benedicts solution (displaces CU² ions)
3. Place in water bath at 100C for 3 minutes (increase rate of reaction as particles gain
kinetic energy and vibrate therefore collide more often)
4. Record colour change in results table 1
5. Put 5cm³ of each solution with no colour change into separate boiling tubes
6. Add 2cm³ hydrochloric acid (to break glycosidic bond between glucose and fructose)
7.…read more

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We added hydrochloric acid to each solution to break the
glycosidic bond between the glucose and fructose molecules and then added sodium
hydrocarbonate to neutralise the acid. Then we added Benedicts solution as in the sucrose
solution there would now be a glucose and a fructose molecule which are both reducing
sugars to react with the Benedicts solution and cause a colour change. Solution B turned
brick red indicating that B was sucrose therefore A was waster.…read more

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General fomula: (CHO)n ­ (n-1)(HO)
Polysaccharides can be straight or branched chains
They are:
Not sweet
Insoluble in water
Non reducing sugars
EG: Starch, Glycogen, Cellulose
Well suited to its function because it is:
Cannot move out the cell in which it is stored
No osmotic effect
Not involved in chemical reactions
Easily hydrolysed into soluble sugars by enzymes when required
Starch molecules are built up into starch grains inside amyloplasts found in the cytoplasm of
plant cells and can also be…read more


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