three important factors which impact the rate at which enzymes catalyze reactions our substrate concentration temperature and pH substrate concentration is important because at very low concentrations many enzymes are just waiting around for a substrate at high concentrations all the enzymes are hard at work and the extra substrates are waiting around for a free enzyme so as substrate concentration increases the amount of enzyme activity saturates as shown in this graph in addition the rate of activity of an enzyme is highest within its optimal temperature range enzyme activity occurs randomly when substrate and enzyme bumped together and bind at low temperatures molecules have low kinetic energy and are unlikely to randomly bump into each other as temperature increases the random interactions happen more frequently as the temperature increases past a certain point however the enzymes start to denature or fall apart resulting in a decrease in enzyme activity enzymes also typically work best in a narrow pH range pH affects enzyme activity by affecting the structure of the enzymes themselves enzymes have many ionizable side chains and prosthetic groups which affect the intermolecular bonds which hold together their secondary and tertiary structure maintaining the correct secondary and tertiary structure is critical for the proper alignment and functioning of the active site outside of an optimal pH range changes to ionizable side chains can break bonds holding together secondary and tertiary structures causing the active site to fall apart and decreasing enzymatic activity in addition the substrate binding to the enzyme might have its own ionizable side chains which can also be affected by pH substrate concentration temperature and pH are not the only factors affecting enzyme activity cells also have some control over enzymatic activity for example they can assert control through the use of post translational mechanisms such as phosphorylation and glycosylation each of which can increase or decrease enzymatic activity in addition cells in different organs produce different enzymes and each cell has control over how much of each enzyme it produces as well as which enzymes go to which organelles for example digestive enzymes are found in the stomach but not in the brain there are also substances that increase enzymatic activity called activators and substances that decrease enzymatic activity called inhibitors inhibitors can interact either reversibly or irreversibly with enzymes reversible inhibitors interact non-covalently with enzymes irreversible inhibitors usually associate with the enzyme through covalent interactions and so decrease the concentration of active enzyme there are three major categories of reversible inhibitors competitive non-competitive and uncompetitive normally a substrate binds to an enzyme at the active site after which the enzyme catalyzes a reaction and releases the products competitive inhibitors compete with the substrate for access to the active site where they bind the enzyme hence they can only bind to free enzymes which are not bound to any substrate non-competitive inhibitors not only bind to free enzymes but also to those bound to substrates this means that they bind not to the active site but to the so called allosteric site in doing so they cause a conformational change that increases or decreases activity of the enzyme uncompetitive inhibitors only bind to enzymes when the enzymes are bound to substrates and they bind in such a way that the enzyme cannot release its products if you liked this video like and subscribe you can also support me by following the link to my patreon if you have any topics you'd like me to cover please leave a comment