THE STRUCTURE AND FUNCTION OF LARGE BIOLOGICAL MOLECULES
The molecules of life
o The four large molecules of all living things are:
- Nucleic Acids
o Carbohydrates, nucleic acids and proteins are large in size thus they
are called macromolecules.
o Macromolecules are chain-like molecules called polymers
o A polymer is a long molecule which contains similar or identical
building blocks linked by covalent bonds.
o Monomers are the smaller molecules that act as a building block for
o A condensation reaction is where two molecules are covalently
bonded together and loses a water molecule.
o It is also called dehydration reaction because a water molecule is lost.
o The dehydration process is helped by enzymes, specialized
macromolecules that speed up chemical reactions in cells.
o Hydrolysis is the reverse of dehydration reaction. It is where a water
molecule is added to break a bond.
o Polymers are broken down to monomers due to hydrolysis.
o They act as fuel and building material.
o They include sugars and polymers of sugars.
o Monosaccharides are also known as simple sugars as it is the simplest
o Disaccharides are double sugars which has two monosaccharides
joined by a dehydration reaction.
o A disaccharide is two monosaccharides joined by a glycosidic linkage,
a covalent bond formed between to monosaccharides by a
o Polysaccharides are macromolecules that are polymers made up of
many sugar building blocks. o Glucose is the most common monosaccharide.
o During cellular respiration, cells use energy in a series of reactions
starting with glucose molecules.
o Polysaccharides are macromolecules, polymers that contains hundreds
to thousands monosaccharides joined by glycosidic linkage.
o Polysaccharides either act as a storage material which is hydrolyzed to
provide sugars for cells or act as a building material for structures that
protects the cell or organism.
o Plants store starch.
o Animals store glycogen.
o Cellulose is a polysaccharide that is a component of tough walls that
surround the plant cells.
o Chitin is a polysaccharide used by arthropods to build their
o The hydrophobic behaviour of lipids is due to their molecular structure.
o Lipids includes: fats, phospholipids and steroids.
o A fat is made up of two kinds of smaller molecules: glycerol and fatty
o A fatty acid has a carbon at one end which is part of a carboxyl
group. This functional group gives it the name of fatty acids.
o Fats separate from water because the water molecules hydrogen-
bond to one another and excludes the fats.
o A saturated fatty acid is when there are no double bonds between
carbon atoms to make the chain so hydrogen atoms are bonded to
the carbon skeleton.
o An unsaturated fatty acid has one or more double bonds formed by
removing hydrogen atoms from the carbon skeleton.
o The tails of the fat molecules has no double bonds which allow the fat
molecules to pack closely together.
o Phospholipids are important in cells because they make up cell
o They only have two fatty acids attached to the glycerol. o The third hydroxyl group