Enzymes

Page 1

Activation Barrier

Molecules that could react with one another often don't and this is due to a lacking of the necessary energy and so before a chemical reaction can occur, the activation energy barrier must be overcome.

For every reaction, there is a specific activation energy - The minimum amount of energy that reactants must possess to give rise to products. (Min energy to reach transition state)

Reactants must reach a chemical stage called the transition state which has free energy higher than that of the initial reactants.

AG °' = difference in free energy between reactions and products.

Page 2

Overcoming the Activation Energy Barrier

Input heat

The energy content of a system can be increased by increasing the temperature as this increases the kinetic energy of molecules.

Increasing temperature can be an issue as using high temperatures are not suitable for biological systems

Alternative approach - Lower the Activation Energy Barrier

This is the task of a Catalyst - an agent which enhances the rate of reaction by lowering the AEB.

Catalysts are not permanently changed or consumed once the reaction is finished - reusable.

Page 3

Enzymes - Protein Catalysts

Some RNA molecules possess enzymatic functions.

Needed in Small Amounts

Speed up reactions

Not consumed or changed in reaction

forward and reverse reactions

Highly Selective

Why are Enzymes Important?

Metabolism

Diagnosis - level of enzymes in blood - indicator of disease

Therapeutics - digestive enzymes