CellDesigner Help

In CellDesigner, a Reaction should have at least one reactant and one product.

If you want to describe a Reaction which represents an independent process (without reactant / product), add a hypothetical "Unknown" Species.

e.g. creation of Calcium and destruction of Calcium, which are both independent. The first process is without a reactant (just the product Calcium) and the second process without a product (just reactant Calcium).