systems biology

Systems biology is a control theorethic approach to biology. It is mainly based on the use of mathematical dynamical description used for gene regulatroy networks.
Gene regulatory networks are the newteorks describing the main genes and gene products relationships. Mostly of this relationship are depicted via pathways.
A pathway is a is a series of chemical reactions occurring within a cell, catalyzed by enzymes, resulting in either the formation of a metabolic product to be used or stored by the cell, or the initiation of another metabolic pathway (then called a flux generating step). Many pathways are elaborate, and involve a step by step modification of the initial substance to shape it into the product with the exact chemical structure desired.
The pathways are mostly qualitative description. Systems biology add a quantitative and systematic information and descritpion.
The first problem is where to find the quantitative information. Once the huge model has been found, many problems are still open. Biological complexity and limited quantitative measurements limit the modelling and simulation of gene networks, relevant and mostly unsolved topics in Systems Biology are:

• Parameter estimation,
• Optimal experimental design
• Identifiability
• Model validation