Why can extremes of ph

The pH of the incubation medium may affect the ionisation of both the substrate and the amino acid side-chains and will therefore this will affect binding. It may also affect the ionisation of reactive groups that catalyse the reaction, although in the micro-environment of the catalytic site, when it is occupied by the substrate, this is less likely.

Extreme values of pH may also disrupt the tertiary structure of the enzyme, and so distort the active site, or even denature the enzyme protein. Different proteins will have different sensitivity to extreme values of pH.

When it is mainly uncharged reactive groups that are involved in the interaction between an enzyme and its substrate, there will be a relatively broad range of pH over which the enzyme has activity. This graph shows the pH dependence of an enzyme that has maximum activity at pH 7.

There would still be measurable activity at pH 6 or pH 8. By contrast, when it is mainly charged groups that are involved in the interaction between an enzyme and its substrate, there will be a relatively narrow range of pH over which the enzyme has activity. Why can extreme pH or temperature cause enzymes to denature? Answered by Lorissa F. Need help with Biology? One to one online tuition can be a great way to brush up on your Biology knowledge.

Answered by Aoife M. A graph to show the effect of temperature on enzyme activity:. Enzymes are also sensitive to pH. Changing the pH of its surroundings will also change the shape of the active site of an enzyme. Many amino acids in an enzyme molecule carry a charge. Within the enzyme molecule, positively and negatively charged amino acids will attract. This contributes to the folding of the enzyme molecule, its shape, and the shape of the active site.

Changing the pH will affect the charges on the amino acid molecules. Amino acids that attracted each other may no longer be. Again, the shape of the enzyme, along with its active site, will change. Extremes of pH also denature enzymes. The changes are usually, though not always, permanent. Enzymes work inside and outside cells, for instance in the digestive system where cell pH is kept at 7. Cellular enzymes will work best within this pH range.

Different parts of the digestive system produce different enzymes. These have different optimum pHs. The optimum pH in the stomach is produced by the secretion of hydrochloric acid.

The optimum pH in the duodenum is produced by the secretion of sodium hydrogencarbonate. The following table gives examples of how some of the enzymes in the digestive system have different optimum pHs:.