University:
Yeshiva University
Course:
BIO1011 | Biology Principles Lectures
Academic year:

2021
Views:

33

Pages:

2
Author:

Stevan J.

Induced fitness hypothesis In this model the enzyme molecule changes shape when the substrate molecule does approaching. The shape change is 'induced' by approaching substrate molecules. This more sophisticated model relies on the fact that molecules are flexible because the single covalent bonds are free to rotate. Factors that influence the work of enzymes The study of changes in reaction rates with experimental parameters such as pH, temperature, enzyme concentration, substrate concentration, the effect of product concentration and the effect of activators is also called enzyme kinetics. 1. Temperature Effects  With increasing temperature, the kinetic energy of the reacting molecules increases. The chance of molecular collisions increases so that the reaction rate increases.  The speed of enzyme reactions increases with increasing temperature up to a maximum called optimal temperature and then decreases.  A bell-shaped curve is observed.  The optimum temperature for most enzymes is between 40° to 45°c. ÿ This is almost 35.5 °C for human body enzymes.  the enzyme denatures and becomes inactive when the temperature is above the optimum. More kinetic energy is possessed when molecules react when the temperature rises. This process increases the probability of success on a collision and increases speed. The catalytic activity of enzymes will reach its peak at a certain temperature. Enzymes in human cells have an optimal temperature of around 37.5oC (human body temperature). As the temperature increases, the enzyme structure begins to break down (changing the properties of an object) because at higher temperatures intra and intermolecular bonds are broken because the enzyme molecules gain more kinetic energy. 2. Effect of pH  Enzyme catalysis requires proper interaction between the enzyme and the substrate. When the pH changes, the charge of the substrate and amino acid residues in the active site changes, thereby reducing the interaction between the enzyme and the substrate resulting in decreased catalysis.  So increasing the pH of the hydrogen ion concentration greatly affects the enzyme activity., a bell-shaped curve is usually obtained.  Each enzyme has an optimum pH for catalysis at which speed is maximum.  Most of the enzymes of higher organisms show activity optimum around neutral pH (6-8). Each enzyme works within a fairly small pH range. There is a pH at which activity is greatest (optimal pH). This is because changes in pH can create and break intra- and intermolecular bonds, changing the shape of the enzyme and, therefore, its effectiveness.