Formation of Macromolecules
- Carbon compounds can be large molecules made from many small, repeating subunits
- Monomers are the smaller units from which larger molecules are made
- Polymers are molecules made from a large number of monomers joined together in a chain
- The process by which monomers join to form polymers is polymerisation
- Macromolecules are very large molecules
- They contain 1000 or more atoms and so have a high molecular mass
- Polymers can be macromolecules, however, not all macromolecules are polymers; polymers must consist of many repeating subunits
- E.g. lipids are not polymers, as they do not consist of repeating monomers
Key biological macromolecules table
Macromolecule | Monomer |
Carbohydrates (polysaccharides) | Monosaccharides |
Lipids | Fatty acids, glycerol, phosphate groups |
Proteins (polypeptides) | Amino acids |
Nucleic acids | Nucleotides |
Formation of macromolecules
- Macromolecules are formed during condensation reactions
- A condensation reaction occurs when molecules combine together, forming covalent bonds and resulting in polymers (polymerisation) or macromolecules
- Water is removed as part of the reaction
Examples of condensation reactions
- Polysaccharides
- Polysaccharides are formed when two hydroxyl (OH) groups on different monosaccharides interact to form a strong covalent bond called a glycosidic bond
Glycosidic bond formation diagram
- Polypeptides
- Polypeptides are formed by condensation reactions
- Two amino acid monomers interact to form a strong covalent bond called a peptide bond
Peptide bond formation diagram
- Nucleic acids
- Separate nucleotides are joined together via condensation reactions to form a phosphodiester bond
- These condensation reactions occur between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide
- It is called a phosphodiester bond because it consists of a phosphate group and two ester bonds
- Separate nucleotides are joined together via condensation reactions to form a phosphodiester bond