Enzymes play many key roles in energy metabolism and homeostatic balance. Without them, cells would be several times more inefficient (if not nonfunctional) in its energy usage, more susceptible to foreign materials, and wouldn’t be able to utilize as many organic materials for energy. Enzymes are proteins. Like all proteins, they are made up of long chains of amino acids transcribed from DNA or RNA templates. They catalyze/accelerate the rate of chemical reactions by lowering the activation energy needed to carry out said reaction. Activation energy is the input of energy required by all chemical reactions to break/synthesize bonds for metabolism in an efficient manner. They accomplish this by stabilizing reactant(s) in their transition state, lowering the amount of free energy released to make it more available, lowering the amount of input energy needed to make or break a chemical bond. Enzymes are also energy efficient because they do not disappear after use and can continue to catalyze reactions. There are several different kinds of enzymes, and each type works on a substrate or reaction. Their specificity comes from the fact that the shape of the enzyme will determine its overall function, so therefore they are tailored to work on one substrate.

All enzymes have special folds in its structure designed to fit a specific substrate, called an Active site. Once a substrate is attached to the active site, a cofactor is normally needed in another receptor or fold of the enzyme for it to perform its function. Cofactors can include Vitamins, co-enzymes (enzymes that work in conjunction with another to form a complex), metal ions, hormones, etc.
Though most enzymes are regulated by cell processes like gene expression, hormone and neurotransmitter release (forms of cell signaling) negative feedback loop with its substrate, or cofactor availability, enzymes are greatly affected by their environment. Its shape can be altered in the presence charged molecules, very susceptible to changes in PH and light, and can be inhibited. Enzyme inhibition is a useful concept to know because inhibitors are used a lot in the medical field in drug therapy, in slowing an unwanted reaction, etc. A most well-known example is penicillin, which inhibits an enzyme used by pathogenic bacteria that repairs damage to its cell wall.

There are three types of enzymatic inhibition: Competitive inhibition, noncompetitive inhibition, and allosteric inhibition. Competitive inhibition occurs when a molecule similar in structure to the substrate binds to its active site, thus preventing it from performing its function (penicillin is an example). Noncompetitive inhibition is when an inhibitor binds to an area other than its active site. They could work by changing its shape or possibly by physically blocking the active site. Lastly, allosteric inhibitors work by adding either an activator molecule to its allosteric site (the site where activators/inhibitors bind to). Examples of allosteric regulators could be hormones, neurotransmitters, or some other type of cell signaling molecule.

References

Biology: How life works (2nd ed.). (2017). In B. A. Berry Andrew, Biology: How life works (2nd ed.) (p. CH 6). McGraw Hill, NY: W. H. Freeman. Retrieved from http://www.macmillanhighered.com/launchpad/morris2e/4909413#/ebook/item/MODULE_bsi__F4951CED__2971__4486__BC4F__E109B2EE87D4/bsi__2ED633B9__F1E8__4C6C__82AA__0633C0C9F474?mode=Preview&toc=syllabusfilter&readOnly=False&renderIn=fne