In most cells, over 90% of the total mass (excluding water) is represented by very large molecules called macromolecules. The macromolecules vary in size from several hundred to several hundred million molecular weight units. Four major classes of macromolecules may be identified; these are the proteins, polysaccharides, lipids, and nucleic acids. The relative amounts of these macromolecules in the "typical" [...]
According to the Bronsted-Lowry definitions, an acid is a proton (or H +) donor and a base is a proton acceptor. For example, when acetic acid is dissolved in water, a certain number of the acetic acid molecules dissociate as follows: In the reaction, a proton of acetic acid has been donated to water, producing an anion (acetate) and a [...]
A molecule is a stable union of two or more atoms. The formation of the bonds that exist between the atoms comprising a molecule requires less energy than that needed to keep the atoms apart. The breakage of the bonds that join atoms consumes energy. If a large amount of energy is required to break the bond, the bond is [...]