Biological Molecules – A Level Biology Notes
1. Carbohydrates
• Monomers: monosaccharides (glucose, galactose, fructose).
• Disaccharides: maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose +
galactose).
• Polysaccharides: starch (amylose + amylopectin), glycogen, cellulose.
• Bond: glycosidic bonds formed by condensation reactions.
2. Lipids
• Not polymers, but made of glycerol + fatty acids.
• Triglycerides: formed by condensation of 1 glycerol and 3 fatty acids.
• Phospholipids: 1 glycerol + 2 fatty acids + phosphate group.
• Properties: hydrophobic tails, hydrophilic heads, form bilayers.
3. Proteins
• Monomers: amino acids.
• Bond: peptide bond via condensation reaction.
• Structure: primary (sequence), secondary (α-helix, β-pleated sheet), tertiary (3D folding),
quaternary (multiple polypeptides).
• Examples: enzymes, antibodies, transport proteins, structural proteins.
4. Nucleic Acids
• DNA & RNA are polymers of nucleotides.
• Nucleotide: phosphate group + pentose sugar + nitrogenous base.
• Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G), Uracil (U in RNA).
• Bonds: phosphodiester bonds, hydrogen bonds between bases.
5. Water
• Polar molecule, hydrogen bonding between molecules.
• Properties: solvent, high specific heat capacity, high latent heat of vaporisation, cohesive
properties, metabolite in reactions.
6. Inorganic Ions
• Examples: Fe²■ (haemoglobin), H■ (pH), Na■ (co-transport of glucose/amino acids), PO■³■
(DNA, ATP).
These notes cover the essential content on Biological Molecules for A-Level Biology.
1. Carbohydrates
• Monomers: monosaccharides (glucose, galactose, fructose).
• Disaccharides: maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose +
galactose).
• Polysaccharides: starch (amylose + amylopectin), glycogen, cellulose.
• Bond: glycosidic bonds formed by condensation reactions.
2. Lipids
• Not polymers, but made of glycerol + fatty acids.
• Triglycerides: formed by condensation of 1 glycerol and 3 fatty acids.
• Phospholipids: 1 glycerol + 2 fatty acids + phosphate group.
• Properties: hydrophobic tails, hydrophilic heads, form bilayers.
3. Proteins
• Monomers: amino acids.
• Bond: peptide bond via condensation reaction.
• Structure: primary (sequence), secondary (α-helix, β-pleated sheet), tertiary (3D folding),
quaternary (multiple polypeptides).
• Examples: enzymes, antibodies, transport proteins, structural proteins.
4. Nucleic Acids
• DNA & RNA are polymers of nucleotides.
• Nucleotide: phosphate group + pentose sugar + nitrogenous base.
• Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G), Uracil (U in RNA).
• Bonds: phosphodiester bonds, hydrogen bonds between bases.
5. Water
• Polar molecule, hydrogen bonding between molecules.
• Properties: solvent, high specific heat capacity, high latent heat of vaporisation, cohesive
properties, metabolite in reactions.
6. Inorganic Ions
• Examples: Fe²■ (haemoglobin), H■ (pH), Na■ (co-transport of glucose/amino acids), PO■³■
(DNA, ATP).
These notes cover the essential content on Biological Molecules for A-Level Biology.
