Introduction to Biological Molecules: Monomers & Polymers in a Snap! Unlock the full A-level Biology course at created by Adam Tisldey biology expert at SnapRevise and current student at Cambridge University studying Biomediacal & Biological Sciences.
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The key points covered in this video include:
1. The Biochemical Basis of Life
2. Biological Molecules
3. Monomers and Polymers
4. Condensation and Hydrolysis Reactions
The Biochemical Basis of Life
When we look at the natural world, we can see that there is an incredible variety of life. Despite this enormous diversity, all life on earth depends on the same biochemical basis of life – this is carbon chemistry. This is because all life is descended from one common ancestor which also used carbon chemistry. Carbon is special because it has the ability to form four bonds. This allows many carbon atoms to be bonded together to form more complex molecules. Carbon therefore acts as a backbone for organic (carbon-containing) molecules that are found in all living organisms.
Biological Molecules
There are four main types of biological molecule which are found in all organisms: carbohydrates, lipids, proteins and nucleic acids. Although based on carbon, these key biological molecules also contain a small number of other chemical elements: Carbohydrates contain carbon, hydrogen and oxygen, lipids mainly contain carbon, hydrogen and oxygen, proteins contain carbon, hydrogen, oxygen, nitrogen and sometimes sulphur, nucleic acids contain carbon, hydrogen, oxygen, nitrogen and phosphorus. These biological molecules contain a very large number of atoms, so they are also known as macromolecules.
Monomers and Polymers
Many biological macromolecules are polymers which are built up from repeating smaller building blocks called monomers. Monomers are individual molecules that make up a polymer. Polymers are long chains that are composed of many individual monomers that have been bonded together in a repeating pattern. In carbohydrates, the monomers are called monosaccharides and the polymers are called polysaccharides. In proteins, the monomers are called amino acids and the polymers are called polypeptides. In nucleic acids, the monomers are called nucleotides and the polymers are called polynucleotides. Lipids are unusual as these are macromolecules that are not polymers – they are not composed of smaller repeating monomers. Lipids are instead made up of a number of different base units which are joined together in a non-repeating pattern.
Condensation and Hydrolysis Reactions
Polymers are formed from monomers by condensation reactions. Condensation reactions involve the bonding of one monomer to another, forming a molecule of water. Water is formed through the grouping of a hydroxyl (-OH) from one monomer and a hydrogen (H) from another monomer. A condensation reaction is a reaction that occurs when two molecules combine to form a more complex molecule with the removal of water.Polymers are broken down into individual monomers by hydrolysis reactions. Hydrolysis reactions require water in order to break the bond between the monomers. A hydrolysis reaction is a reaction that occurs when larger molecules are broken down into smaller molecules with the addition of water. Condensation and hydrolysis reactions are used to build up and break down all biological macromolecules. Condensation and hydrolysis reactions are reactions that take place within an organism – so they are examples of metabolic reactions.
Summary
All living organisms have the same biochemical basis of life – biological molecules are all organic (carbon-containing)
Many biological macromolecules are polymers, including carbohydrates, proteins and nucleic acids
Polymers are long chains that are composed of many individual monomers that have been bonded together in a repeating pattern
Monomers are individual molecules that make up a polymer
Not all macromolecules are polymers e.g. lipids
Condensation reactions are used to build up polymers and hydrolysis reactions are used to break down polymers
A condensation reaction is a reaction that occurs when two molecules combine to form a more complex molecule with the removal of water
A hydrolysis reaction is a reaction that occurs when larger molecules are broken down into smaller molecules with the addition of wate
