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A theory expressing the idea that life on Earth passed through an era when biological processes were carried out predominantly by ribonucleic acids, without the involvement of deoxyribonucleic acids or proteins. The RNA World theory (or hypothesis)…

A chemical compound, (CH3)2CO; the first member of the homologous series of aliphatic ketones. Acetone (see illustration) is a colorless, volatile, and flammable liquid. Acetone occurs naturally in plants and animals. Its physical properties include…

In the Brönsted classification, an acid is any chemical species, ionic or molecular, capable of donating a proton (hydrogen ion) to another substance; the other substance acts as a base in accepting the proton. For these two interrelated classes of…

One of a large group of organic substances possessing the halocarbonyl group in which X stands for fluorine, chlorine, bromine, or iodine. The terms acyl and aroyl halides refer to aliphatic or aromatic derivatives, respectively.The great inherent…

The branch of mathematics dealing with the solution of equations. These equations involve unknowns, or variables, along with fixed numbers from a specified system (Fig. 1). The origins of algebra were based on the need to develop equations that…

The study of zero sets of polynomial equations. Examples of zero sets of polynomial equations studied in algebraic geometry are the parabola y − x2 = 0, thought of as sitting in the (x, y)-plane, and the locus of all points (t, t2, t3, t4), which is…

Any compound having highly basic properties, strong acrid taste, and ability to neutralize acids. Aqueous solutions of alkalies are high in hydroxyl ions, have a pH above 7, and turn litmus paper from red to blue. Caustic alkalies include sodium…

The elements of group 1 in the periodic table. Of the alkali metals, lithium differs most from the rest of the group, and tends to resemble the alkaline-earth metals (group 2 of the periodic table) in many ways. In this respect lithium behaves as do…

Usually calcium, strontium, and barium, the heaviest members of group 2 of the periodic table (excepting radium). Other members of the group are beryllium, magnesium, and radium, sometimes included among the alkaline-earth metals. Beryllium…

A nonsteroidal anti-inflammatory drug used to control pain, fever, and inflammation. Aspirin is one of the most prevalent medicines in the world and is used to reduce fever and treat minor aches, pains, and inflammation. Furthermore, it is the only…