Catalytic activity is the acceleration of chemical reactions by a substance that is not modified in the process. In biological systems, enzymes regulate catalysis, reducing the energy required for reactions. Enzymes are essential for cellular functions and are regulated by feedback inhibition and environmental changes.
Catalytic activity is the increase in the rate and energy of a chemical reaction by a substance that is not itself modified in the reaction. In biological systems, it is performed by enzymes essential for normal life processes. By reducing the energy required to initiate a reaction, enzyme pathways increase the rate at which cells perform essential chemical functions. Catalysis is controlled by enzyme regulation. Some of these involve modifications to the enzymatic structure, while others operate by altering the cellular environment in which the catalytic activity takes place.
In general chemistry, catalytic activity or catalysis is any change – increase or decrease – in the rate of a reaction by an agent that is not chemically changed by the process. In industry, this can mean any number of agents used to increase the rate and yield of reactions, but in biochemistry, catalytic activity refers to the work of enzymes, the proteins found in all organisms that mediate most part of cellular functions, including metabolism. Very few biological processes would occur at a rate sufficient to sustain life without enzymatic catalysis.
Some reactions would not occur at all without the catalytic activity of enzymes. Normally, many molecules have an energy barrier to react together. Called the activation energy, this limit must be exceeded for chemical reactions to proceed.
In some cases, a high activation energy threshold means that the reactants are unlikely to react on their own or will do so at a slow rate. When enzymes temporarily bind to one or more reactants, the required activation energy is reduced and the reaction rate accelerates. Enzymes can also inhibit the activation of other enzymes and slow down the process.
Enzyme activity often results in multi-step biochemical reactions, each of which relies on a different catalyst and depends on the product of the previous step. Physically, the catalytic activity of many different enzymes occur in the same cell organelle, thereby accelerating the rate of reaction. Changes in pH and temperature can, to some extent, work synergistically to increase the rate of catalysis. Temperatures over a certain range can damage the protein structure of an enzyme, rendering it incapable of activity.
In biological systems, the catalytic activity is regulated by several mechanisms. Enzymes usually consist of inactive precursor proteins and these only become active through the action of another enzyme or an environmental change such as movement from inside the cell to the outside. Feedback inhibition reduces catalysis when the product of one or more enzyme pathways accumulates in the cell, blocking further release or production of the enzyme that catalyzed the initial reaction. Likewise, small amounts of the reaction products will increase the production of the enzyme.
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