BIOLOGY_ENZYMES

=I. CHEMICAL REACTIONS & ENZYMES= Reactans - elements or compunds that enter into a chemical reaction Products - the elemnts or compounds produced by a chemical reaction
 * Enzymes** are proteins that catalyze (//i.e.//, increase the rates of) chemical reactions.[1][2] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.Chemical reaction - a process that changes or transforms, one set of chemicals into another.

What happens to chemical bonds during chemical reactions?
 * Chemical reations involve changes in the chemical bonds that join atoms in compounds.

Energy Changes** Chemical reactions that release energy often occus on their own, or spontaneously. Chemical reactions that absorb energy will not occus withou a source of energy.

In order to stay alive, organisms need to carry out reactions that require energy. Plants ge tthat energy by trapping and storing the energy from sunligh in energy-rich compounds. Animals get their energy when the consume plants or other animals.
 * Energy Sources**

Chemical reactions that release energy do not always occur spontaneouly. Chemists call the energy that is needed to get a reaction started the **activation energy.**
 * Activation Energy**