Control of Metabolism Through Enzyme Regulation
Cellular needs and conditions vary from cell to cell and change within individual cells over time. For example, stomach cells require different amounts of energy than skin cells, fat storage cells, blood cells, and nerve cells. The same stomach cell may also need more energy immediately after a meal and less energy between meals.
Enzymes ultimately determine which chemical reactions a cell can carry out and the rate at which they can proceed. These chemical reactions determine a cell's function. A cell's functions are usually defined by its chemical reactions, so enzymes generally determine a cell's function as well. By lowering the activation energy of a chemical reaction, enzymes promote chemical reactions that are specific to the cell's function.
Competitive and Noncompetitive Inhibition
The cell uses specific molecules to regulate enzymes to either promote or inhibit certain chemical reactions. In competitive inhibition, an inhibitor molecule is similar enough to a substrate that it can bind to the active site and simply block the substrate from binding . In noncompetitive inhibition, an inhibitor molecule binds to the enzyme at a location other than the active site (an allosteric site). The substrate can still bind to the enzyme, but the inhibitior changes the shape of the enzyme so it is no longer in optimal position to catalyze the reaction.
Source: Boundless. “Control of Metabolism Through Enzyme Regulation.” Boundless Biology. Boundless, 03 Jul. 2014. Retrieved 16 Jan. 2015 from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/metabolism-6/enzymes-72/control-of-metabolism-through-enzyme-regulation-351-11577/