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Alevel AQA biology - biological molecules (unit 1) AS
These are my notes for the first unit of alevel biology - biological molecules! I got an A in my alevel AQA biology exam using these notes. Happy revising :)
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Biological molecules,Can you explain that all living thing
have the same biochemical basis?
• All living organisms share the same biochemistry – all have the sam
amino acids to build proteins, nucleic acids (DNA + RNA) as genetic
material and carbon- based compounds
,Molar solution
• A solution that contains one mole of solute in each litre of solution
• e.g. Sodium chloride (NaCl)
• 23 + 35.5 = 58.5
• One mole of NaCl contains 58.5g of solute in each litre of solution
,Carbohydra
tes
,Polymerisation
POLYMERISATION = monomers are linked together to form a long ch
called a polymer
• Monomers are linked together to form a polymer which releases a
molecule of water
• This is called a condensation reaction
• If you add a molecule of water, the polymer breaks up into its
monomers
• This is called hydrolysis
,Monosaccharides
• Soluble
• Examples are glucose, fructose and galactose
• Glucose has 2 isomers – a glucose and b glucose
,Test for reducing sugars
(monosaccharides )
• Add reducing sugar to test tube
• Add Benedict's reagent to test tube
• Heat in water bath for 5 minutes
• Insoluble brick- red precipitate forms
Benedict's reagent is alkaline and is copper (II) sulphate. When heate
with reducing sugar, it forms an insoluble red precipitate of copper (I
oxide.
Benedict's reagent is SEMI-QUANTATIVE (you can estimate the amou
of reducing sugar in a sample)
,Test for non-reducing sugars
(disaccharides)
• Add non-reducing sugar to test tube
• Add Benedict's reagent to test tube
• Heat in water bath for 5 minutes
• You will get a negative result (benedict's will remain blue- no reducing sug
• Add hydrochloric acid and heat in a water bath for 5 minutes. This hydroly
non reducing sugar (disaccharide) into reducing sugars (monosaccharides
• Add sodium hydrogencarbonate to neutralise hydrochloric acid. This is
because Benedict's is alkaline and doesn’t work in acidic conditions
• Add reducing sugar to another test tube and add Benedict's and heat in
water bath for 5 minutes. It will form a brick red precipitate.
,Reducing and non-reducing sugars
, Monosaccharide + monosaccharide = disaccharid
Many monosaccharides = polysaccharide
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