These can be associated with active site of an enzyme. A. SubstrateB. Competitive inhibitorC. Cofactor

In conjugated enzymes, the cofactors are associated with the active site at the time of catalysis or prior to catalysis. The substrate structure is complementary to the active site of enzyme and hence it can also associate with the enzyme. Since competitive inhibitors are structural analogues of substrate, they can also bind to active site and prevent the conversion of substrate into products.