The Building Blocks of Biology

Essay by toyaplayUniversity, Bachelor'sA+, April 2005

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Select a molecule. List the atoms that that molecule is composed of and describe the type of bond that holds those atoms together. Be sure to explain how this bond works.

In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. A molecule consists of two or more atoms joined by shared pairs of electrons in a chemical bond. It may consist of atoms of the same chemical element, as with oxygen (O 2), or of different elements, as with water (H 2O). A substance that consists of molecules is a molecular substance or molecular compound.

3D (left and center) and 2D (right) representations of the terpenoid, atisane. In the 3D model on the left, carbon atoms are represented by gray spheres, white spheres represent the hydrogen atoms and the cylinders represent the bonds. The model is enveloped in a mesh representation of the molecular surface, colored by areas of positive (red) and negative (blue) electric charge.

In the 3D model (center), the light-blue spheres represent carbon atoms, the white spheres are hydrogen atoms, and the cylinders in between the atoms correspond to single-bonds.

Most molecules are much too small to be seen with the naked eye. A property of molecules is the integer ratio of the elements that constitute the compound, the empirical formula. For example, in their pure forms, water is always composed of a 2:1 ratio of hydrogen to oxygen, and ethyl alcohol or ethanol is always composed of carbon, hydrogen, and oxygen in a 2:6:1 ratio. However, this does not determine the kind of molecule uniquely - dimethyl ether has the same ratio as ethanol, for instance. Molecules with the same atoms in different arrangements are called isomers.

Chemical formula on the other hand...