Nucleotides are building blocks of nucleic acids. Each nucleotide is a composite molecule formed by 

1.	base-sugar-phosphate
2.	base-sugar-OH
3.
4.	sugar-phosphate

ATP is:

Given below is the diagrammatic representation of one of the categories of small molecular weight organic compounds in the living tissues. Identify the category shown and the one blank component X in it :
     

1. Category: Cholesterol; Component: Guanine
2. Category: Amino acid; Component: NH₂
3. Category: Nucleotide; Component: Adenine
4. Category: Nucleoside; Component: Uracil