AQA AS BIOLOGY 7401/1 PAPER 1 VERSION: 1.0 FINAL
CERTIFIED QUALITY EXAM GRADED A+ UPDATED 2026
Formation of disaccharides
Formed from the condensation of two monosaccharides
Examples of disaccharides and how they are formed
Maltose: a disaccharide formed by the condensation of two
glucose molecules.
Sucrose: a disaccharide formed by condensation of a fructose
molecule and a glucose molecule.
Lactose: a disaccharide formed by condensation of a galactose
molecule and a glucose molecule.
Alpha-glucose and beta-glucose isomers structure
Why do large molecules often contain carbon
Most polymers are based on carbon, hydrogen, oxygen and
nitrogen
,Polysaccharides
Polymers, formed by combining together many
monosaccharide molecules
Very large molecules and so are insoluble - makes them
suitable for storage
When they are hydrolysed, they break down into disaccharides
and monosaccharides.
E.g. Cellulose - not used for storage, give structural support to
plant cells
Starch - used for storage, made up of chains of alpha-glucose
linked by glycosidic bonds formed by condensation reactions,
chains may be branched or unbranched
Formation of polysaccharides
Formed from the condensation of many glucose units
Gycogen and starch: formed from the condensation of alpha-
glucose
Cellulose: formed by the condensation of beta-glucose
, Basic structure and functions of glycogen
STRUCTURE:
Shorter chains than starch and is more highly branched
FUNCTIONS:
Carbohydrate storage in animals, structurally suited for
because:
- insoluble so does not tend to draw water into cells by
osmosis
- insoluble so does not diffuse out of cells
Compact so a lot can be stored in a small space
- more highly branched than starch so has more ends that can
be acted on simultaneously by enzymes so is therefore more
rapidly broken down to form glucose monomers, which are
used in respiration - important because animals have a higher
metabolic rate and therefore respiratory rate than plants
because they are more active.
Basic structure and functions starch
STRUCTURE:
Made up of chains of alpha-glucose linked by glycosidic bonds
formed by condensation reactions.
CERTIFIED QUALITY EXAM GRADED A+ UPDATED 2026
Formation of disaccharides
Formed from the condensation of two monosaccharides
Examples of disaccharides and how they are formed
Maltose: a disaccharide formed by the condensation of two
glucose molecules.
Sucrose: a disaccharide formed by condensation of a fructose
molecule and a glucose molecule.
Lactose: a disaccharide formed by condensation of a galactose
molecule and a glucose molecule.
Alpha-glucose and beta-glucose isomers structure
Why do large molecules often contain carbon
Most polymers are based on carbon, hydrogen, oxygen and
nitrogen
,Polysaccharides
Polymers, formed by combining together many
monosaccharide molecules
Very large molecules and so are insoluble - makes them
suitable for storage
When they are hydrolysed, they break down into disaccharides
and monosaccharides.
E.g. Cellulose - not used for storage, give structural support to
plant cells
Starch - used for storage, made up of chains of alpha-glucose
linked by glycosidic bonds formed by condensation reactions,
chains may be branched or unbranched
Formation of polysaccharides
Formed from the condensation of many glucose units
Gycogen and starch: formed from the condensation of alpha-
glucose
Cellulose: formed by the condensation of beta-glucose
, Basic structure and functions of glycogen
STRUCTURE:
Shorter chains than starch and is more highly branched
FUNCTIONS:
Carbohydrate storage in animals, structurally suited for
because:
- insoluble so does not tend to draw water into cells by
osmosis
- insoluble so does not diffuse out of cells
Compact so a lot can be stored in a small space
- more highly branched than starch so has more ends that can
be acted on simultaneously by enzymes so is therefore more
rapidly broken down to form glucose monomers, which are
used in respiration - important because animals have a higher
metabolic rate and therefore respiratory rate than plants
because they are more active.
Basic structure and functions starch
STRUCTURE:
Made up of chains of alpha-glucose linked by glycosidic bonds
formed by condensation reactions.
