Is optimum ph for enzyme 7-14?

Lord no. You need to be specific on which enzyme. Some prefer slightly acidic, some neutral, some slightly basic, however non in the range 8-14 that I know of

its given in a reference book 4-7...is it correct ?

The optimum pH for an enzyme can vary depending on the specific enzyme and its function. However, a pH range of 7-14 is not applicable for most enzymes. The majority of enzymes have an optimum pH that falls within the range of 6-8. This is because enzymes are sensitive to changes in pH, and their activity can be significantly affected by pH levels that are too acidic (below 6) or too basic (above 8).

To determine the optimum pH for a specific enzyme, scientists typically conduct experiments using a range of pH values and measure the enzyme's activity at each pH level. They can then plot a graph known as a pH-activity profile to determine the pH at which the enzyme exhibits maximum activity.

It's important to note that some enzymes have specific pH requirements that differ from the general range of 6-8. For example, pepsin, an enzyme involved in digestion, has an optimum pH of around 2 in the stomach due to the highly acidic conditions. On the other hand, trypsin, another digestive enzyme, has an optimum pH of around 8 in the small intestine where the pH is more alkaline.

Therefore, it's crucial to consider the specific enzyme and its biological environment when determining its optimal pH.