What Are The Enzymes?

An enzyme is a biocatalyst made up of protein, and like other catalysts, it accelerates the rate of reaction without itself being used up. Almost all reactions in living organisms take place directly or indirectly under the influence of enzymes. As catalysts, their function is to accelerate the attainment of equilibrium in reversible reactions by catalysing both the forward and reverse reactions. Therefore, it is expected that one and the same enzyme system would catalyse the breakdown of a substance and its synthesis.

The substance upon which an enzyme acts is known as a substrate. Most enzymes are named after their substrate by adding the suffix – 'ase'. Thus maltase acts on maltose, uricase on uric acid and so on. Even general term such as proteinases and lipases are employed depending upon the group of substances they act on. Certain enzymes are named after their function, e.g. oxidases catalyse oxidations, dehydrogenases bring out removal of hydrogen.

All enzymes are protein in nature. However, some enzymes, in addition to the protein part, also consist of an organic non-protein component and if the latter is loosely attached to the enzyme protein, it is called co-enzyme.

Enzymes are proteins that trigger off activities in the body's cells, but they are not affected in any way by the activities they set off.  They are needed to bring about bio-chemical reactions and are also the catalysts for a number of chemical reactions in the cells of the body.

Enzymes are chemical substances that occur naturally in the human body. When an organ of the body is injured, such as the heart in case of a heart attack, certain enzymes or chemicals, such as LDH, SGOT and CPK, are released. These are complex protein-based catalysts. Each enzyme has a specific function and a specific effect on the body. Enzymes are able to trigger off bio-chemical reactions in the body without changing their form. If a certain enzyme is not present in the body, it can lead to an imbalance in the metabolic rate of the person and pose a severe health hazard.

Enzymes are the most important group of proteins which are biologically active. They tremendously increase the efficiency of a biochemical reaction and are specific for each type of reaction. Without these enzymes the reaction would proceed at a very slow speed making life impossible.

Enzymes are composed of hundreds of amino acids joined together and coiled upon them to form a globular structure. The catalytic activity is restricted to a small portion of the structure known as the active site. The reactant called substrate is attached to the active site consisting of only a few amino acids, while rest of the bulk of the amino acids maintains the globular structure of the enzyme.

Some enzymes consist solely of proteins. Others also have a non-protein part known as a co-factor which is essential for the proper functioning of the enzymes. The co-factor usually acts as "Bridge" between the enzyme and its substrate, often it contributes directly to the chemical reactions which bring about catalysis. Sometimes the co-factor provides a source of chemical energy, helping to drive reactions which would otherwise be difficult or impossible. Some enzymes use metal ions as co-factors like Mg2 +, Fe2, Cu2+, Zn2+ etc.

I believe a enzyme is a molecule.  Enzymes would be a group of molecules.  However, I would still see what others here have to say and wait for some more answers to come in.