Networks and pathways

In any biological system, for example, bacteria, cultured human stem cells, or cells interacting in tissues, a variety of networks and pathways are responsible for the basic functioning and robustness of the system. Examples of networks and pathways are:

Metabolic pathways

Krebs cycleFor example, the famous Krebs cycle (Noble prize awarded in 1953). The Krebs cycle, also known as the citric acid cycle, is central to the chemical processing of carbohydrates, fats, and proteins to produce energy. The image gives a glimpse of the complexity of a metabolic pathway.

Cell signaling pathways

Cell SignalThese are part of a complex system of communication through which cells perceive and respond to their environment.

Heat shock response

Protein foldingThe process whereby cells counter the effect of heat, which causes protein unfolding and malfunction.

The human immune system

This is a network of proteins, cells, organs, and tissues that interact in intricate ways to maintain good health.

The immune system in action

Cancer cellsnpblood cells

Because biological networks are complicated regulatory systems, one expects that feedback will play an important role and that there will be similarities with man-made control systems. The goal in applying methods from systems and control theory to biological systems, now known as systems biology, is to gain a deeper understanding of the design principles of biological organization. This knowledge is being applied extensively in developing biotechnology, for example:

  • E coliIn medicine, using new understanding of disease processes to develop cures.
  • In metabolic engineering one modifies the genetic structure of cells in order to increase their efficiency in producing some desired substance. 
  • In one example of metabolic engineering, genes from the bacteria E.coli were inserted into the bacteria M.methylotrophus. The modified bacteria were more efficient at converting methanol into proteins used in animal feed.
  • In bioremediation, that is, in modifying and adapting micro-organisms to help clean up contaminated areas.