19. It is a very stable, string of repeating units of polymers. ________________ 20. It is composed of a phosphate, a sugar and four nitrogenous bases. _____ 21. It can act as both an acid and a base due to the presence of the amino and carboxyl functional groups. _______________ 22. It consists of ribose nucleotides attached by phosphodiester bonds. _______ 23. A test used to detect genetic material. ______________________ 24.A test used to detect the presence of carbohydrates. ________________ 25. A test used to determine the presence of protein material. ________________