The given graph shows the effect of substrate concentration on the rate of reaction of the enzyme green gram phosphatase. What does the graph indicate?

 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 .
          

        Category                            Component
   1    Nucleotide                               Adenine
   2    Nucleoside                              Uracil
   3    Cholesterol                              Guanin
   4    Amino acid                                NH₂