Caveats

Caveats concerned with the "high-energy bond" in biochemistry and cell biology texts of some years ago:

From: Joseph S. Fruton and Sofia Simmonds, General Biochemistry, John Wiley & Sons, Inc., New York, 1959; p 380.

"It should be added that the term "bond energy" as used by some biochemists in connection with 'energy-rich" and "energy-poor" bonds has a meaning different from "bond energy" as defined in physical chemistry, where it refers to the mean delta-H0 required to break a bond between 2 atoms. Thus the bond energy of the O–H bond is 110 kcal per mole, and that of a C–C bond is 58 kcal per mole; more energy is required to break the O–H bond."

From: Edward S. West, Wilbert R. Todd, Howard S. Mason and John T. Van Bruggen, Textbook of Biochemistry, 4th ed; The Macmillan Co., New York, 1966; p 887.

"It is important to understand that the expression "high-energy compound" or "high-energy bond" as used in biochemistry, has a meaning quite different from the physiochemical significance of "high-energy bond". In physical chemistry, a high-energy bond is one which requires large amounts of thermochemical energy for dissociation. Thus the P–O bond requires about 80 kcal/mol for dissociation, and is stable compared to the O–O bond in H2O2, which requires 35 kcal/mol; a high thermochemical bond energy is associated with unfavorable tendency toward splitting reactions. In biochemistry, on the other hand, the expression "high-energy bond" refers to the large free energy decreases associated with definite reactions of that bond, such as hydrolysis or group transfer. A "high-energy compound" is not a substance with a high thermochemical dissociation energy, but a substance the biological reaction of which are associated with large free energy decreases-that is, they tend to go to completion."

From: John W. Kimball, Cell Biology, 2nd ed; Addison-Wesley Publishing, New York,1978; p. 145.

"It is important to note that in using the expression 'high-energy' for these bonds, we are not referring to bond energy, the concept that we discussed at length in Chapter 1. Here the term simply refers to the fact that the products of the hydrolysis of the so-called high-energy bonds have substantially less free energy than the reactants. Really, then, these are weak bonds with low bond energies. However, the concept of the 'high-energy' bonds of ATP (and ADP) is so entrenched that we shall retain it. In illustrations, we shall also observe the convention of indicating these bonds by a wavy line."

From: Albert L. Lehninger. Biochemistry, 2nd ed; Worth Publishing, Inc.New York, 1979; p. 401-402

"The term phosphate bond energy sometimes used by biochemists is not to be confused with the term bond energy used by the physical chemists, which denotes the energy required to break a bond between two atoms. Actually, a relatively large amount of energy is required to break a covalent chemical bond which would not exist if it were not quite stable. Although we do break a P–O bond during hydrolysis of phosphate esters, a new P–O bond is formed."

Discussions of the "high-energy bond" in specialized texts of some years ago:

From: Irving M. Klotz; Introduction to Biomolecular Energies, Academic Press, Orlando, 1986: p 52

"The implication of the name high-energy bond is that there is a concentration of energy between P~P that tends to make the terminal phosphate fly off whenever possible; however, the P~P bond will not spontaneously spring open. Actually, we would have to put energy into ATP (approximately 10^5 cal/mole) to remove the terminal phosphate group or, more explicitly, to break the distal P–O–P bonding: This energy which must be forced into the molecule to break a bond between two atoms is what is called the bond energy. On the other hand, the biochemist is not really interested in the change in internal energy necessary to break the P–O bond, but rather in the change in chemical potential (or free energy) when a compound such as ATP transfers one of its substituent groups to another molecule."

From Albert L. Lehninger; Bioenergetics, The Molecular Basis of Biological Energy Transformations; 2nd ed; W.A. Benjamin, Inc., Menlo Park, 1971; pp 41-42.

"Those phosphorylated compounds having a strongly negative standard free energy of hydrolysis, such as ATP, are often spoken of as having high-energy phosphate bonds, and such bonds are universally designated by the symbol ~P. These terms are very useful to biochemists, but they may be a little misleading to the beginner. The term "high-energy phosphate bond" may imply that the energy spoken of is in the bond and that when the bond is split, energy is set free. This is not correct. In the ordinary usage of physical chemistry, bond energy is defined as the energy required to break a given bond between two atoms. Actually, relatively enormous energies are required to break chemical bonds, which would not exist if they were not stable. The term "phosphate bond energy" does not refer to the bond energy of the covalent linkage between the phosphorus atom and the oxygen or nitrogen atom; rather, it denotes the difference in energy content of the reactants and products…."

The caveats of this type that appeared in texts in the past are much less common in current texts. Some exceptions are:

Biology Campbell and Reece
Biology Online Kimball
Biochemistry, Lehninger

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