Unit One – Lifestyle, Health and Risk
A macromolecule is a giant molecule made from many repeating units. In Biology, polymers are long chains of biological molecules made up of units that can be pulled apart to form more simple substances e.g. starch can be broken down into glucose monomers. A polymer is formed when monomers link together. In order to do this a simple reaction occurs to bond the monomers together. This is called a condensation reaction and is where a molecule of water is removed. Not all polymers link this way, but starch and proteins do.
Carbohydrates are a very large group of biological molecules, with diverse functions. They are compounds containing carbon, hydrogen and oxygen. They are the most abundant organic compounds found in nature being produced by green plants and photosynthetic bacteria:
6CO2 + 6H2O → C6H12O6 + 6O2
The small, simple ones are metabolic i.e. part of the cell’s reactions e.g. glucose, fructose, maltose. The larger ones are used for storage (of glucose) e.g. starch in plants and glycogen in animals. They are also structural e.g. cellulose in plant cell walls.
These are the simplest of the sugars, containing only one unit or monomer. They are sweet, soluble crystalline molecules of low molecular mass. Each contains an aldehyde (- CHO) or a ketone (- C=O) group. Monosaccharides have at least 3 carbon atoms in the molecule and the name ends in –ose. e.g:
Triose = 3-C sugar glyceraldehyde
Pentose = 5-C sugar ribose (in RNA)
Hexose = 6-C sugar glucose, fructose
How to build a glucose molecule:
The formula is C6H12O6 . Each carbon atom is bonded to another carbon, a hydrogen and a hydroxyl group (-OH) (except carbon 1, which has no –OH as it forms part of the aldehyde group). This can be written as a straight chain: