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Summary AQA Biology A-Level notes, Unit 1 - Biological molecules (7402)- based on specification
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AQA A-Level Biology notes for Module 1 biological molecules. Based on official AQA specification.
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Biological MoleculesCARBOHYDRATES
what are monomers
Monomers are the smaller units from which larger molecules are made
what are polymers
Monomers are the smaller units from which larger molecules are made
3 examples of monomers
Monosaccharides, amino acids and nucleotides
describe a condensation reaction
A condensation reaction joins two molecules together with the formation of a
chemical bond and involves the elimination of a molecule of water
describe a hydrolysis reaction
A hydrolysis reaction breaks a chemical bond between two molecules and
involves the use of a water molecule
explain the formation of polymers
monomer sub units are joined together by a condensation reaction to form
polymers. This process is called polymerisation.
explain the breakdown of polymers
polymers are broken down by hydrolysis through the addition of water
molecules breaking the bonds that link the sub units of a polymer and
therefore splitting the molecule into its constituent parts
what are monosaccharides
Monosaccharides are the monomers from which larger carbohydrates are
made
three examples of monosaccharides
Glucose, galactose and fructose
what is a reducing sugar
A reducing sugar is a sugar that can donate electrons to (or reduce) another
chemical
Biological Molecules 1
, test for reducing sugars
All monosaccharides and some disaccharides are reducing sugars.
Benedict's I reagent is an alkaline solution of copper(II) sulfate. When a
reducing sugar is heated with Benedict's reagent it forms an insoluble red
precipitate of copper(I) oxide.
1. add 2cm3 of the food sample to be tested to a test tube. If the sample is
not already in liquid form, first grind it up in water.
2. add an equal volume of Benedict's reagent
3. heat the mixture gently in a boiling water bath for 5 minutes
4. the higher the concentration of reducing sugar the further right the colour
change goes
test for non reducing sugars
1. If the sample is not already in liquid form, it must first be ground up in
water
2. Add 2cm3 of the food sample being tested to 2cm3 of Benedict's
reagent in a test tube and filter
3. place the test tube in a gently boiling water bath for 5 minutes. If the
Benedict’s reagent does not change colour then a reducing sugar is not
present
4. Add another 2cm3 of dilute hydrochloric acid in a test tube and place it in
gently boiling water for 5 minutes. This will hydrolyse any disaccharide
present into its constituent monosaccharides
5. slowly ass some sodium hydrogen carbonate solution to the test tube to
neutralise the dilute HCl (benedict's reagent does not work in acidic
conditions).
6. Test the solution with pH paper to check the solution is alkaline
7. Re-test the solution by heating it with 2cm3 of benedict's reagent in a
gently boiling water bath for 5 minutes
Biological Molecules 2
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