AQA A Level Biology
Topic 1
Biological molecules
Model answer notes by @biologywitholivia
e
Topic Understand Memorise Practise
1.1 Monomers & polymers
1.2 Carbohydrates
1.3 Lipids
1.4.1 General properties of proteins
1.4.2 Many proteins are enzymes
Required practical 1
1.5.1 Structure of DNA and RNA
1.5.2 DNA replication
1.6 ATP
1.7 Water
1.8 Inorganic ions
,AQA A Level Biology Topic 1 Biological molecules biologywitholivia.co.uk
1.1 Monomers and polymers
What are monomers and polymers?
● Monomers - smaller / repeating molecules from which larger molecules / polymers are made
● Polymer - molecule made up of many identical / similar molecules / monomers
What happens in condensation and hydrolysis reactions?
Condensation ● 2 molecules join together Hydrolysis ● 2 molecules separated
reaction ● Forming a chemical bond reaction ● Breaking a chemical bond
● Releasing a water molecule ● Using a water molecule
Give examples of polymers and the monomers from which they’re made
Exam insight: common mistakes
Mistake Explanation
*Mixing up hydrolysis and ‘C’ for condensation; ‘C’ for connecting molecules. Imagine
condensation reactions.* condensation on a window to remember water is released.
*Forgetting to include H2O in diagrams of 1 H2O molecule is released for every condensation reaction
condensation and hydrolysis reactions.* and 1 H2O molecule is used for every hydrolysis reaction.
“Lipids are polymers.” Lipids are not made from repeating monomers.
“A polymer is made of two ‘Poly’ means many. Two monomers joined
or more monomers.” together is a dimer.
2
, AQA A Level Biology Topic 1 Biological molecules biologywitholivia.co.uk
1.2 Carbohydrates
What are monosaccharides? Give 3 common examples
● Monomers from which larger carbohydrates are made
● Glucose, fructose, galactose
Describe the structure of α-glucose
● Left - full structure, carbon
atoms labelled
● Right - simplified structure
as in the specification to
be memorised for exam
Describe the difference between the structure of α-glucose and β-glucose
OH group is below carbon 1 in α-glucose Alpha & beta glucose are isomers →
but above carbon 1 in β-glucose same molecular formula, differently arranged atoms
What are disaccharides and how are they formed?
● Two monosaccharides joined together with a glycosidic bond
● Formed by a condensation reaction, releasing a water molecule
List 3 common disaccharides & monosaccharides from which they’re made
Disaccharide Monosaccharides
Maltose Glucose + glucose
Sucrose Glucose + fructose
Lactose Glucose + galactose
Draw a diagram to show how two monosaccharides are joined together
What are polysaccharides and how are they formed?
● Many monosaccharides joined together with glycosidic bonds
● Formed by many condensation reactions, releasing water molecules
3
Topic 1
Biological molecules
Model answer notes by @biologywitholivia
e
Topic Understand Memorise Practise
1.1 Monomers & polymers
1.2 Carbohydrates
1.3 Lipids
1.4.1 General properties of proteins
1.4.2 Many proteins are enzymes
Required practical 1
1.5.1 Structure of DNA and RNA
1.5.2 DNA replication
1.6 ATP
1.7 Water
1.8 Inorganic ions
,AQA A Level Biology Topic 1 Biological molecules biologywitholivia.co.uk
1.1 Monomers and polymers
What are monomers and polymers?
● Monomers - smaller / repeating molecules from which larger molecules / polymers are made
● Polymer - molecule made up of many identical / similar molecules / monomers
What happens in condensation and hydrolysis reactions?
Condensation ● 2 molecules join together Hydrolysis ● 2 molecules separated
reaction ● Forming a chemical bond reaction ● Breaking a chemical bond
● Releasing a water molecule ● Using a water molecule
Give examples of polymers and the monomers from which they’re made
Exam insight: common mistakes
Mistake Explanation
*Mixing up hydrolysis and ‘C’ for condensation; ‘C’ for connecting molecules. Imagine
condensation reactions.* condensation on a window to remember water is released.
*Forgetting to include H2O in diagrams of 1 H2O molecule is released for every condensation reaction
condensation and hydrolysis reactions.* and 1 H2O molecule is used for every hydrolysis reaction.
“Lipids are polymers.” Lipids are not made from repeating monomers.
“A polymer is made of two ‘Poly’ means many. Two monomers joined
or more monomers.” together is a dimer.
2
, AQA A Level Biology Topic 1 Biological molecules biologywitholivia.co.uk
1.2 Carbohydrates
What are monosaccharides? Give 3 common examples
● Monomers from which larger carbohydrates are made
● Glucose, fructose, galactose
Describe the structure of α-glucose
● Left - full structure, carbon
atoms labelled
● Right - simplified structure
as in the specification to
be memorised for exam
Describe the difference between the structure of α-glucose and β-glucose
OH group is below carbon 1 in α-glucose Alpha & beta glucose are isomers →
but above carbon 1 in β-glucose same molecular formula, differently arranged atoms
What are disaccharides and how are they formed?
● Two monosaccharides joined together with a glycosidic bond
● Formed by a condensation reaction, releasing a water molecule
List 3 common disaccharides & monosaccharides from which they’re made
Disaccharide Monosaccharides
Maltose Glucose + glucose
Sucrose Glucose + fructose
Lactose Glucose + galactose
Draw a diagram to show how two monosaccharides are joined together
What are polysaccharides and how are they formed?
● Many monosaccharides joined together with glycosidic bonds
● Formed by many condensation reactions, releasing water molecules
3
