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Page 1

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Biological Molecules
A) Describe how hydrogen bonding occurs between water molecules, and
relate this, and other properties of water, to the roles of water in living
organisms


Hydrogen is slightly positive
Oxygen is slightly negative
Polar molecule
Hydrogen bond (covalent bonding)



Properties of water

Solvent ­ solute/solution
Liquid ­ transport…

Page 2

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C) Describe with the aid of diagrams the formation and breakage of
peptide bonds in the synthesis and hydrolysis of dipeptides and
polypeptides
Synthesis

Condensation reaction
Peptide bond forms
Water (H2O) released

Hydrolysis

Water (H2O) used
Peptide (covalent) bond broken



D) Explain, with the aid of diagrams, the term, primary…

Page 3

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Coils / folds even further
Hydrogen bonds
Disulphide bridges ­ two molecules
of an amino acid close together, the
sulphur atoms bond together
(cysteine)
Ionic interactions - weak attractions
between oppositely charged parts
the molecule
Hydrophilic/Phobic interaction
(Philic outside/Phobic inside ­
globular)




G) Explain with the aid of diagrams the…

Page 4

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I) Compare the structure & function of a structural (collagen) and globular
(haemoglobin) protein


Haemoglobin (globular) Collagen (fibrous)
Soluble in water Insoluble in water
Prosthetic group (Haem) No prosthetic group
Large range of amino acids in primary 35% primary structure is glycine
structure
Many alpha helix structures Many Left-handed helix…

Page 5

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Alpha (H on top)
Beta (H below)
Glucose + glucose = Maltose
Glucose + fructose = sucrose




L) Describe with the aid of diagrams, the formation and breakage of
glycosidic bonds in the synthesis and hydrolysis of a disaccharide
(maltose) and a polysaccharide (amylose)




Condensation reaction
1-4 Glycosidic bond
Water…

Page 6

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Glycogen

Alpha glucose
Animal store
Unbranched 1-4 (amylose)
Branched 1-6 (amylopectin)
Stored ­ Muscle & Liver
More branched
Shorter 1-4 links
Insoluble



Cellulose

Beta glucose
Long straight chains
Cross link hydrogen bonds
Many micro-fibrils = Macro-fibrils




O) Explain how the structures of
glucose, starch (amylose), glycogen and cellulose molecules relate…

Page 7

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Triglyceride

1 glycerol
3 fatty acids
Condensation reaction
Forms ester bonds
Insoluble in water
Hydrophobic

Phospholipid

1 glycerol
2 fatty acids
1 phosphate group
Condensation reaction
Forms ester bonds
Hydrophilic ­ Phosphate head
Hydrophobic ­ fatty acid tails




Q) Explain how the structure of triglycerides, phospholipids and cholesterol
molecules relate…

Page 8

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R) Describe how to carry out chemical tests to identity the presence of the
following molecules:


Protein ­ Biuret test
Reducing/Non-Reducing sugars ­ Benedict's test
Starch ­ Iodine solution
Lipids ­ Emulsion test

Proteins

Add the biuret reagent
Biuret reagent is pale blue
Contains ­ sodium hydroxide + copper sulphate…

Page 9

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Lipids

Add with ethanol ­ dissolves the lipids
Add to water
If lipids are present ­ white emulsion will form on top layer



S) Describe how the concentration of glucose in a solution may be
determines using a colorimeter


Benedict's test ­ reducing sugars (glucose)
Results in orange/red precipitate
The…

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