1. Proteins are made from subunits called amino acids. There are 20 different amino acids which are responsible for the variation of proteins. Those amino acids are linked together by peptide bonds and form polypeptide chains. According to the polypeptide structure, there are 4 levels in protein structure as primary structure, secondary structure, tertiary structure and quaternary structure.
2. Starch is a type of carbohydrate. Hence, the subunits of starch are sugar molecules which are called as glucose. The elements of glucose are C,H,O. By linking glucose units with 1-4 alpha glycosidic bonds, the polysaccharide chain is formed. Hence, starch is also a polysaccharide.
3. DNA is made from subunits called nucleotides. Nucleotides consist of deoxyribose, phosphate group and nitrogenous base.
There are two types of nitrogenous base as purines and pyrimidines. Adenine (A) and guanine (G) are purines and
thymine (T) and cytosine (C) can be seen as pyrimidines. Those nucleotides are linked together by sugar phosphate bonds which are formed between 5' phosphate group and 3' -OH group.
