Name: Introduction to Biochemistry
Uploaded: 2019-07-19
Duration: 3 min 55 s
Description: Biochemistry allows us to understand the large biomolecules that run our cellular functions, like proteins, carbohydrates, and DNA. Know the basics of biochemistry here.

Question

Describe the role of temperature, pH and substrate affecting enzymatic activity.

Accepted Answer

The enzymes are composed of proteins. The external factors including temperature, pH plays an essential role in the activity of enzyme.The role of temperature, pH and substrate on enzymatic activity is disscussed below.
(i) Temperature: An enzyme works best within a narrow range of temperature. The temperature at which an enzyme shows its highest activity is called optimum temperature for that particular enzyme. It generally corresponds to the body temperature of warm blooded animals. For example, 37°C in human beings. Enzyme activity decreases above and below this temperature. Enzyme becomes inactive below minimum temperature and beyond maximum temperature. Low temperature helps in the preservation of the enzymes in the inactive state.
(ii) Optimum pH: Every enzyme has an optimum pH when it acts on the substrate most effectively. A rise or fall in pH reduces enzyme activity by changing the degree of lonisation of its side chains. Most of the intracellular enzymes function near neutral pH with the exception of several digestive enzymes which work either in acidic range of pH or alkaline, e.g., 2.0 pH for pepsin, 8.5 for trypsin.

(iii) Substrate Concentration. Increase in substrate concentration increases the rate of reaction. The enhanced rate is due to two factors :
(a) The occupation of more and more active sites by the substrate molecules;
(b) Higher number of collisions between substrate molecules. The rise in velocity is quite high in the beginning but it decreases progressively with the increase in substrate concentration. If a graph is plotted for substrate concentration versus reaction velocity, it appears as a hyperbolic curve. A stage is reached where velocity is maximum. It does not increase further by increasing the substrate concentration. At this stage the enzyme molecules become fully saturated and no active site is left free to bind additional substrate molecules. This saturation effect is shown by all enzymes.

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