Question

1) Describe how free energy (Delta G) of a reaction can tell us if a reaction will occur or not.

2) Enzymes catalyze chemical reactions. How do enzymes increase the rate of a reaction? What is the active site of the enzyme?

Answer 1

1) Delta G is the gibbs free energy. It shows the spontaneity of a reaction ( natural occurance with out an external force ). For a reaction to occur spontaneously, the gibbs free energy must be negative. If the delta G of a reaction is a negative value, the reaction will occur spontaneously. If the delta G value of the reaction is positive, the reaction will not occur naturally. For a reaction whose delta G value is positive, we need to apply an external force inorder to undergo the reaction in forward direction. Otherwise that reaction will not happen.

2) Enzymes are used to increase the rate of a reaction. Enzymes are biological catalysts. They increase the rate of reaction by reducing the activation energy required for the reaction. In a reaction, it begins from the reactants and it goes to a transition state and ends up being the product. Activation energy is the free energy which is required by the reactants or added to the reactants inorder to reach the transition state. A reaction moves forward only if it aquires the energy to reach the transition state. By reaching the transition state, it can then form the products. Adding enzymes reduce the rate of reaction by reducing this activation energy. If the activation energy of a reaction is less, the reaction rate will be faster.

Active site of an enzyme : It is the site of an enzyme , where it binds with the substrate of a reaction. This binding is temporary. The active site of the enzyme consists of the aminoacid residues which helps them to bind temporarily with the substrate. During a reaction, the substrate binds with the active site of the enzyme and undergo the reaction to form the products and the product then gets detached from the active site of the enzyme and the enzyme is free.