Living organisms should be able to transform matter and energy into different forms, show response to changes in their environment and show growth and reproduction. All living organisms undergo changes due to large organic compounds called macromolecules. Four main types of macromolecules control all activities. They are proteins, carbohydrates, nucleic acids and lipids.
What are macromolecules?
A very large molecule made up of smaller units called monomers. The monomers may be the same or slightly different. Only a few monomers can recombine to create a lot of different combinations—this gives the diversity of macromolecules. Macromolecules are formed by dehydration reactions in which water molecules are removed from the formation of bonds.
Carbohydrates typically have CnH2nOn formula. There are three types of carbohydrates, monosaccharides contain one sugar, disaccharides contain two sugars, and polysaccharides contain many sugars. Polysaccharides play important roles in cells such as energy storage (animal glycogen) and structure support (plant cellulose).
Proteins are made of C, H, O, N and S. The building units of proteins are amino acids. Each amino acid contains an amino group, a carboxyl group, a central carbon and hydrogen, and an R group. Variation on R group defines different amino acids. There are 20 different amino acids. Proteins have 4 layers of structure, primary structure --Number and sequence of amino acids, secondary structure --Coiling and folding from H bonds, Tertiary structure-- 3-dimensional shape from increased folding, and quaternary --Peptide chains combine to make a functional protein.
Lipids are made of carbon, hydrogen and oxygen. Storage lipids include fats, oils and waxes. Mono-carboxylic acids, containing a long hydrocarbon side chain. Based on the nature of the hydrocarbon side chain, they are divided into saturated fatty acids (no double bonds) and unsaturated fatty acids (containing double bonds). Biological membranes have a double layer of lipids which are amphipathic in nature.
Nucleic acids are made of carbon, oxygen, hydrogen, nitrogen and phosphate. The basic building blocks of nucleic acids are nucleotides. Each nucleotide has three basic parts: a nitrogenous base, phosphate group and a sugar. There are two types of nucleic acids, DNA and RNA. DNA is long, linear double strand molecule; RNA is shorter and single strand. DNA and RNA are genetic material, carrying all the codes for the functioning of the cell. They also have the keys to heredity and the ability to make new cells.