Question

Topic: The Free Energy and Equilibria of Entropy

Description: Biological systems differ from chemical systems when it comes to equilibrium. In a chemical system once equilibrium is met, no other reactions occur. In a biological system, a dynamic equilibrium is used when a substrate is turned into a product, another reaction creates the same substrate thus keeping the concentrations stagnant. This allows for cells to continually make new compounds without messing the Delta G for the systems.

Instructions: Write a response to the following prompt 200-250 words.

Prompt: Propose what would happen if a living cell all the sudden reached chemical equilibrium. Also discuss the effects of build up of a particular substrate on a biological system. How would this affect overall delta G’s?

Answer 1

Chemical equilibrium:

In case of chemical reaction the reaction will continue until the system reaches a balance point, i.e where the forward and reverse reactions take place at same rate. In chemical equilibrium the overall concentration of products and reactants remains constant. The reaction system has lowest possible energy state at equilibrium.

Cells and equilibrium

If a living cell all the sudden reached chemical equilibrium, assuming an isolated system, its chemical reactions would reach equilibrium, which will not support the life of cell. If a cell's reaction reached equilibrium, the cell would die because there would not be any free energy left to perform various activities to keep cell alive. Cells require energy in the form of ATP to import reactant molecules, to export product molecules.

Effect of buildup of particular substrate:

In biological system substrate builds up favors backward reaction. If the change in Gibbs free energy (∆G) is positive the reaction is spontaneous in reverse direction, i.e the products (E+S) is disassociated in to Enzyme and Substrate. Due to this substrate build will be taking place.

Over all Change in Free energy

Build up of particular Substrate in biological system means the concentration of reactants (E and S) are more. That means the products (E+S) is converting in to E and S. In this case the reaction is favored in reverse direction and it need energy, so the change in overall Free energy is Positive or reaction is Endothermic (Endergonic).