Question

How does PH influence enzyme activity? How might a change in environmental pH due to acid precipitation or carbon dioxide pollution impact an ecosystem?

Answer 1

A number of enzymes perform their activity through acid base catalysis. In this mechanism rate of reaction is accelerated by the addition by the addition of an or a base. Proton donor and acceptor groups present in the enzyme stabilise the transition state and hence reduce the activation energy. Most enzymes show optimal activity between pH 5 and 9 and the pH value at which they show maximum activity is the optimum pH of that enzyme. Extreme pH values can denature the enzyme and reduce the enzyme activity by distorting the conformation of the active site. Distorted active sites then no longer binds with the substrate and don’t produce any product. Moreover functional groups present in the active site have particular charges and the alterations in the pH might affect those ionisable groups and would result in the decline of enzyme activity.

Acid precipitation due to the pollution of oxides of sulphur or nitrogen or carbon dioxide pollution can change the environmental pH and has many adverse ecological effects. Acid rain in the water bodies will decrease the pH of the aquatic ecosystem like ponds, rivers, lakes, oceans etc. This decreased pH can affect the life of acid sensitive organisms like corals in the sea. Decreased sea pH is causing coral bleaching. Most fish eggs cannot hatch below pH value 5. Acidic rain water can leach aluminum from soil clay particles and then flow into the aquatic ecosystem.

Acid rain weakens hard plants by washing away the protective film on leaves, and it reduces growth .Acid rain also depletes the useful nutrients from the soil that plants need.