Protein is a macromolecule made up of many amino acids which joins by peptide bond.
A polypeptide chain is formed of a linear row of amino acids, joined by peptide bonds. This constitutes the primary structure. Secondary structure is of two main types α-helix and β pleated. In α-helix a single amino acid is coiled spirally by forming hydrogen bonds between first and fourth amino acids. α-helical model of protein was given by Pauling and Corey.
Watson and Crick gave double hellx model of DNA.
Robertson gave "unit membrane model" for blological membrane.
Dixon and Jolly gave cohesion. transpiration pull theory to explain ascent of sap.