Carbohydrates are polymers of monosaccharides joined by glycosidic bonds. The 3 main ones you can do research about are cellulose, glycogen and starch.
Proteins are polymers of amino acids joined by peptide bonds and their structures vary lots because of their primary, secondary and tertiary structure. You could research common ones like haeomoglobin, collagen, elastin, etc
Nucleic acids are polymers of nucleotides joined by phosphodiester bonds and these refer to DNA, RNA and ADP.
Hopefully these are some good ideas to help you get started :-)
You could easily get 25 marks out of this :-)