🧬 Biological Molecules Overview
This section covers the key facts about biological molecules, including monomers,
polymers, carbohydrates, and lipids, essential for A-level biology.
🧱 Monomers and Polymers
• Monomers:
Smaller units that can create larger molecules. Examples include glucose, amino acids,
and nucleotides (RNA or DNA).
• Polymers:
Made from many monomers bonded together. Examples include starch, cellulose,
glycogen (from glucose), proteins (from amino acids), and DNA/RNA (from nucleotides).
💧 Condensation and Hydrolysis
• Condensation Reaction: Joins two molecules together, creating a chemical bond
and removing water.
• Hydrolysis Reaction: Breaks apart or splits monomers by breaking a chemical
bond between two molecules, involving the use of water.
🍬 Carbohydrates
Overview of the three levels of size of the molecules you need to know:
• Monosaccharide: One sugar unit (mono = one).
• Disaccharide: Two sugar units joined together (di = two).
• Polysaccharide: Many sugar units joined together.
Examples of Carbohydrates
Category Examples
Monosaccharides Glucose, Fructose, Galactose
Disaccharides Sucrose, Maltose, Lactose
Polysaccharides Starch, Cellulose, Glycogen
🔬 Structure of Alpha and Beta Glucose
• Molecular Formula: C6H12O6C6 H12 O6
, • Isomers: Glucose exists as two isomers, alpha and beta glucose, which have the
same molecular formula but different structures.
o Alpha Glucose: On carbon one, the hydrogen atom is on top, and the
hydroxyl group is on the bottom.
o Beta Glucose: On carbon one, the hydroxyl group is on top, and the
hydrogen atom is on the bottom.
🔗 Disaccharides Formation
• Made up of two monosaccharides.
• The chemical bond that forms is a glycosidic bond.
• Created via a condensation reaction.
Disaccharide Equations
• Maltose: Glucose + Glucose + Water
• Lactose: Glucose + Galactose + Water
• Sucrose: Glucose + Fructose + Water
🌱 Polysaccharides
• Starch and Cellulose: Found in plants with different functions. Starch stores
glucose for chemical energy, while cellulose provides structural strength in the cell
wall.
• Glycogen: Found in animals, mainly in the liver and muscle cells, as a store of
glucose.
Polysaccharide Details
Featur
e Starch Cellulose Glycogen
Monom Alpha Glucose Beta Glucose Alpha Glucose
er
Bonds 1-4 and 1-6 glycosidic bonds 1-4 glycosidic bonds 1-4 and 1-6
glycosidic bonds
Structu Amylose (unbranched, helix), Long, straight chains in Highly branched
re Amylopectin (branched) parallel, forming fibrils
Functio Glucose storage in plants Structural strength in plant Glucose storage in
n cell walls animals
Locatio Plants Plant cell walls Liver and muscle
n cells in animals
This section covers the key facts about biological molecules, including monomers,
polymers, carbohydrates, and lipids, essential for A-level biology.
🧱 Monomers and Polymers
• Monomers:
Smaller units that can create larger molecules. Examples include glucose, amino acids,
and nucleotides (RNA or DNA).
• Polymers:
Made from many monomers bonded together. Examples include starch, cellulose,
glycogen (from glucose), proteins (from amino acids), and DNA/RNA (from nucleotides).
💧 Condensation and Hydrolysis
• Condensation Reaction: Joins two molecules together, creating a chemical bond
and removing water.
• Hydrolysis Reaction: Breaks apart or splits monomers by breaking a chemical
bond between two molecules, involving the use of water.
🍬 Carbohydrates
Overview of the three levels of size of the molecules you need to know:
• Monosaccharide: One sugar unit (mono = one).
• Disaccharide: Two sugar units joined together (di = two).
• Polysaccharide: Many sugar units joined together.
Examples of Carbohydrates
Category Examples
Monosaccharides Glucose, Fructose, Galactose
Disaccharides Sucrose, Maltose, Lactose
Polysaccharides Starch, Cellulose, Glycogen
🔬 Structure of Alpha and Beta Glucose
• Molecular Formula: C6H12O6C6 H12 O6
, • Isomers: Glucose exists as two isomers, alpha and beta glucose, which have the
same molecular formula but different structures.
o Alpha Glucose: On carbon one, the hydrogen atom is on top, and the
hydroxyl group is on the bottom.
o Beta Glucose: On carbon one, the hydroxyl group is on top, and the
hydrogen atom is on the bottom.
🔗 Disaccharides Formation
• Made up of two monosaccharides.
• The chemical bond that forms is a glycosidic bond.
• Created via a condensation reaction.
Disaccharide Equations
• Maltose: Glucose + Glucose + Water
• Lactose: Glucose + Galactose + Water
• Sucrose: Glucose + Fructose + Water
🌱 Polysaccharides
• Starch and Cellulose: Found in plants with different functions. Starch stores
glucose for chemical energy, while cellulose provides structural strength in the cell
wall.
• Glycogen: Found in animals, mainly in the liver and muscle cells, as a store of
glucose.
Polysaccharide Details
Featur
e Starch Cellulose Glycogen
Monom Alpha Glucose Beta Glucose Alpha Glucose
er
Bonds 1-4 and 1-6 glycosidic bonds 1-4 glycosidic bonds 1-4 and 1-6
glycosidic bonds
Structu Amylose (unbranched, helix), Long, straight chains in Highly branched
re Amylopectin (branched) parallel, forming fibrils
Functio Glucose storage in plants Structural strength in plant Glucose storage in
n cell walls animals
Locatio Plants Plant cell walls Liver and muscle
n cells in animals
