Wednesday, August 1, 2012

Explain the effect of temperature on the rate of an enzyme-controlled reaction.

Answer:

The effect of temperature on an enzyme-catalysed reaction.

At low temperatures, an enzyme-controlled reaction occurs very slowly. The molecules in solution move slowly and take a longer time to bind to active sites. The enzymes are said to be ineffective.

Theoretically, temperature is directly proportional to the rate of reaction. Increasing temperature increase the kinetic energy of the reactants. As the reactant molecules move faster, they increase the number of collisions of molecules to form to form enzyme-substrate complex.

At optimum temperature, the rate of reaction is at maximum. The enzyme is still in an active state. However the optimum temperature varies with different enzymes. For example, the enzymes in our body function best at about 37 celsius, such as salivary amylase, pepsin, trypsin and lipase.

At above optimum temperature, the enzyme molecules become denatured. The increased kinetic energy causes the atoms of the enzyme molecules to vibrate violently. The hydrogen and ionic bonds which help to hold the specific three-dimensional shape of enzyme molecules are broken. The effect is irreversible. The substrates cannot longer fit into the altered shape of the active site to undergo a reaction. The rate of reaction decreases rapidly.

Assignment submitted by S.M., Kang, E.S., Ong, T.W., Tan, K.Y., Ho. X.H., Wong 2011/2012 (IBM)

STPM BIOLOGY