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AS BIOLOGY
REVISION GUIDE 2009 FOR UNIT 2



AS Biology

Biological Molecules (Biochemistry)

Carbohydrates
Proteins
Fats (Lipids)
Water (WE ALREADY KNOW THIS FROM UNIT 1)

Carbohydrates

Made from basic sugars (e.g. Glucose) ­ known as a monosaccharide.
Two monosaccharides form a DISACCHARIDE, by a condensation
(loss of Water), in between…

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AS BIOLOGY
REVISION GUIDE 2009 FOR UNIT 2



Polysaccharides

Amylose is simply poly(14) glucose, so is a
straight chain. In fact the chain is floppy, and it
tends to coil up into a helix.


Amylopectin is poly(14) glucose with about 4%
(16) branches. This gives it a more open
molecular…

Page 3

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AS BIOLOGY
REVISION GUIDE 2009 FOR UNIT 2




If there are no C=C double bonds in the hydrocarbon chain, then it is a saturated fatty
acid (i.e. saturated with hydrogen). These fatty acids form straight chains, and have a
high melting point.
If there are C=C double bonds in the…

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AS BIOLOGY
REVISION GUIDE 2009 FOR UNIT 2



Amino acids are joined together by peptide bonds. The reaction involves the formation of a
molecule of water in another condensation polymerisation reaction:



















Protein Structure
Polypeptides are just a string of amino acids, but they fold up to form the complex and…

Page 5

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AS BIOLOGY
REVISION GUIDE 2009 FOR UNIT 2




The sheet. The
polypeptide chain
zigzags back and
forward forming a
sheet. Once again it is
held together by
hydrogen bonds.
3. Tertiary Structure
This is the 3 dimensional structure formed by the folding up of a whole polypeptide
chain. Every protein…

Page 6

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AS BIOLOGY
REVISION GUIDE 2009 FOR UNIT 2



This diagram shows a molecule of the enzyme This diagram shows part of a molecule of
dihydrofolate reductase, which comprises a collagen, which is found in bone and
single polypeptide chain. It has a globular shape cartilage. It has a unique, very…

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