Factors affecting enzymatic reaction 2

a)      pH

·         Enzymes are sensitive to pH.pH is a measure of the hydrogen concentration. It is measured on a scale of 1-14 with pH 7 being the neutral point. A pH less than 7 is acidic wheareas greather than 7 is alkaline.

·         The precise three-dimensional molecular shape which is vital to the functioning of enzymes is partly the result of hydrogen bonding between positive and negative charges in the enzyme molecule. By breaking the hydrogen bonds which give enzyme molecules their shape any change in pH can effectively denature enzyme.

·         These bonds may be broken by the concentration of hydrogen ion present. In other words a change of pH environment of the protein alters the ionic charge of the acidic and basic groups and causes the protein to change. This changes the shape of the active site of the enzyme and the enzyme may no longer have the correct shape to bind to its substrate

·         Each enzyme has its own range of pH in which it functions most efficiently. Most intracellular enzymes function best at around neutral. If the pH is too low or too high the activity will fall. pH sensitivity is due to acidic and basic side groups of amino acids.

·         Enzymes are adapted to the pH of their environment. They have optimal activity at a certain pH.

 D) Temperature

·         As the temperature increases the kinetic energy of the substrate and enzyme molecule increase and so they move faster. The faster these molecules move, the more often they collide with one another and the greater the rate of reaction.

·         Enzymes function best at a particular temperature known as their optimum temperature.

·         Enzymes are inactive by excessive heat. Up to about 40^oC, the rate of an enzyme-controlled reaction increases smoothly, a 10^oC rise in temperature approximately doubles the rate of the action. Above 40^oC the rate begins decrease and at about 60 ^oC the reaction stops.

·         This is caused by the denatured of protein which constitutes the enzyme. As the temperature increases the more the atoms which make up the enzyme molecule vibrate. Above a critical temperature, enzyme activity falls rapidly because the enzyme unfolds. This break the hydrogen bonds which hold the molecules in their precise shape.

The three-dimensional shape of the enzyme molecule is altered to such an extent that their active sites no longer fit the substrate. The enzyme is said to be denatured and it loses its catalytic properties. Heat sterilization