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MODULE 1
BIOLOGICAL
MOLECULES
BIOLOGY
NOTES
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INDEX
TOPIC 1 MONOMERS AND POLYMERS. . . . . . . . . . . . . . . . . 5
TOPIC 2 CARBOHYDRATES. . . . . . . . . . . . . . . . . . . . . . . . 7
TOPIC 3 LIPIDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
TOPIC 4 PROTEINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1. The General Properties of Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2. Many Proteins are Enzymes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
TOPIC 5 NUCLEIC ACIDS . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Structure of DNA and RNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2. DNA Replication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
TOPIC 6 ATP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
TOPIC 7 WATER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
TOPIC 8 INORGANIC IONS. . . . . . . . . . . . . . . . . . . . . . . 35
3
TOPIC 1
Monomers
and
Polymers
Monomers and Polymers
On the whole, living organisms consist of the same materials:
Carbohydrates
Lipids
Nucleic
Acids
Proteins
Carbon
ü
ü
ü
ü
Hydrogen
ü
ü
ü
ü
ü
Oxygen
ü
ü
ü
ü
ü
Nitrogen
ü
ü
Phosphorus
ü
Water
Monomers and polymers
•• Monomers are individual molecules that can bond to other identical monomers to form a
string of such molecules called a polymer
•• E.g. a chain of identical glucose molecules (monomers) is a polymer called starch.
•• Monosaccharides, nucleotides and amino acids are examples of monomers.
Condensation Reaction
•• A reaction in which two molecules join together and
•• Release a water molecule
•• E.g. when two glucose molecules bond together
•• conversely, a water molecule is used to split two glucose molecules: this is called
Hydrolysis Reaction
•• Very common phenomenon in biology, especially with enzymes
•• Inverse of condensation: two molecules split and use up a water molecule to do so
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TOPIC 2
Carbohydrates
Carbohydrates
Disaccharide = macromolecule consisting of 2 sugar molecules joined by a glycosidic bond
Polysaccharide = macromolecule consisting of more than 2 sugars — often a long chain
polymer — joined together by glycosidic bonds
Two sugar molecules join together by a glycosidic bond (shown below):
Glycosidic Bond
•• Repeats between thousands of sugar monomers to form a polysaccharide
○○ A polysaccharide is not a sugar
•• If just two sugar monomers bond, they form a specific disaccharide
•• Form by a condensation reaction
•• Broken by hydrolysis
•• Generally 1,4-glycosidic bonds
Beaning the bond forms between Carbon atom 1 and Carbon atom 4
EXAM TIP
You should be aware of the different combinations of sugar that form different
disaccharides:
•• Glucose + Fructose = Sucrose (found in sugar cane)
•• Glucose + Galactose = Lactose (found in milk)
•• a-Glucose + a-Glucose = Maltose (found in germinating seeds)
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