Biology A Level Revision (AQA)
Paper 1 - Year 12 / AS Level
Biological Molecules
Cells
Organisms Exchanging Substances
Genetic Information, Variation
Paper 2 - Year 13 / A Level
Energy Transfers In and Between Organisms
Organisms Responses to their Environment
Genetics, Evolution and Ecosystems
The Control of Gene Expression
Some diagrams used in this document are sourced from Cognito (https://cognitoedu.org).
All rights to those diagrams belong to Cognito.
, Biology Revision A Level AQA
Biological Molecules
Monomers and Polymers
● Monomers
- Single subunits or building blocks of life.
● Polymers
- Complex molecules that are formed by
combining monomers.
- Uses covalent bonds
● Condensation
- Smaller biological
molecules can be joined
together to form larger
molecules used in the
body which help the
organism survive.
- Condensation is the
joining of two monomers
that releases water and
creates a bond.
- This forms a polymer
which is a larger molecule.
- Amino acids join to form proteins.
- Monosaccharides join to form carbohydrates.
- Fatty acids and glycerol join to form lipids.
● Hydrolysis
- Larger molecules can then
be broken back down into
smaller molecules.
- Hydrolysis is the breaking
of a bond between two
monomers.
- Hydrolysis also requires
water.
- Proteins break down into
amino acids.
- Carbohydrates break down
into monosaccharides.
- Lipids break down into fatty acids and glycerol.
Page 1
, Biology Revision A Level AQA
Carbohydrates - Monosaccharides + Test
- Formed from Carbon, Oxygen and Hydrogen.
● Monosaccharides
- Simple sugars such as:
1. Glucose (alpha / beta).
2. Fructose.
3. Galactose.
● Glucose
- Is a hexose sugar with chemical formula C₆H₁₂O₆.
- Important source of energy as made during cellular respiration
and used to form ATP.
- Alpha ( ) and Beta (ꞵ) glucose are isomers of each other as
they have the same molecular formula but a different
arrangement in their structure.
- Hydroxyl groups have a different orientation on Carbon 1.
● Disaccharides
- Glucose + Glucose → Maltose
- Glucose + Fructose → Sucrose (Found in table sugar)
- Glucose + Galactose → Lactose (Found in milk)
● Testing for Sugars
- Benedict’s solution is used to test for reducing and non-reducing sugars.
- All monosaccharides are reducing sugars and some disaccharides are.
- Test for Reducing Sugars :
1. Place 2 ml of the substance in a boiling tube (liquid form).
2. Add 10 drops of Benedict’s Solution.
3. Place in boiling water for 3-5 minutes.
- Test for Non Reducing Sugars :
1. Boil in dilute HCl to hydrolyse non-reducing sugars.
2. Neutralise with Sodium Hydrogen Carbonate.
3. Repeat the test for reducing sugars.
- Colour Changes:
➢ Blue → Blue - No Reducing Sugar Present.
➢ Blue → Green/Yellow -
Traces of Reducing
Sugars.
➢ Blue → Orange -
Moderate amounts of
Reducing Sugars.
➢ Blue → Brick Red -
Large amounts of
Reducing Sugars.
Page 2
Paper 1 - Year 12 / AS Level
Biological Molecules
Cells
Organisms Exchanging Substances
Genetic Information, Variation
Paper 2 - Year 13 / A Level
Energy Transfers In and Between Organisms
Organisms Responses to their Environment
Genetics, Evolution and Ecosystems
The Control of Gene Expression
Some diagrams used in this document are sourced from Cognito (https://cognitoedu.org).
All rights to those diagrams belong to Cognito.
, Biology Revision A Level AQA
Biological Molecules
Monomers and Polymers
● Monomers
- Single subunits or building blocks of life.
● Polymers
- Complex molecules that are formed by
combining monomers.
- Uses covalent bonds
● Condensation
- Smaller biological
molecules can be joined
together to form larger
molecules used in the
body which help the
organism survive.
- Condensation is the
joining of two monomers
that releases water and
creates a bond.
- This forms a polymer
which is a larger molecule.
- Amino acids join to form proteins.
- Monosaccharides join to form carbohydrates.
- Fatty acids and glycerol join to form lipids.
● Hydrolysis
- Larger molecules can then
be broken back down into
smaller molecules.
- Hydrolysis is the breaking
of a bond between two
monomers.
- Hydrolysis also requires
water.
- Proteins break down into
amino acids.
- Carbohydrates break down
into monosaccharides.
- Lipids break down into fatty acids and glycerol.
Page 1
, Biology Revision A Level AQA
Carbohydrates - Monosaccharides + Test
- Formed from Carbon, Oxygen and Hydrogen.
● Monosaccharides
- Simple sugars such as:
1. Glucose (alpha / beta).
2. Fructose.
3. Galactose.
● Glucose
- Is a hexose sugar with chemical formula C₆H₁₂O₆.
- Important source of energy as made during cellular respiration
and used to form ATP.
- Alpha ( ) and Beta (ꞵ) glucose are isomers of each other as
they have the same molecular formula but a different
arrangement in their structure.
- Hydroxyl groups have a different orientation on Carbon 1.
● Disaccharides
- Glucose + Glucose → Maltose
- Glucose + Fructose → Sucrose (Found in table sugar)
- Glucose + Galactose → Lactose (Found in milk)
● Testing for Sugars
- Benedict’s solution is used to test for reducing and non-reducing sugars.
- All monosaccharides are reducing sugars and some disaccharides are.
- Test for Reducing Sugars :
1. Place 2 ml of the substance in a boiling tube (liquid form).
2. Add 10 drops of Benedict’s Solution.
3. Place in boiling water for 3-5 minutes.
- Test for Non Reducing Sugars :
1. Boil in dilute HCl to hydrolyse non-reducing sugars.
2. Neutralise with Sodium Hydrogen Carbonate.
3. Repeat the test for reducing sugars.
- Colour Changes:
➢ Blue → Blue - No Reducing Sugar Present.
➢ Blue → Green/Yellow -
Traces of Reducing
Sugars.
➢ Blue → Orange -
Moderate amounts of
Reducing Sugars.
➢ Blue → Brick Red -
Large amounts of
Reducing Sugars.
Page 2
