Biological thermodynamics
Encyclopedia
Biological thermodynamics is a phrase that is sometimes used to refer to bioenergetics
, the study of energy transformation in the biological sciences. Biological thermodynamics may be defined as the quantitative study of the energy transductions that occur in and between living organisms, structures, and cells and of the nature and function of the chemical processes underlying these transductions. Biological thermodynamics may address the question of whether the benefit associated with any particular phenotypic
trait is worth the energy investment it requires.
' 1957 book Energy Transformations in Living Matter (written with Hans Kornberg
) was the first major publication on the thermodynamics of biochemical reactions. In addition, the appendix contained the first-ever published thermodynamic tables, written by K. Burton, to contain equilibrium constants and Gibbs free energy
of formations for chemical species, able to calculate biochemical reactions that had not yet occurred.
Non-equilibrium thermodynamics
has been applied for explaining how biological organisms can develop from disorder. Ilya Prigogine
developed methods for the thermodynamic treatment of such systems. He called these systems dissipative systems, because they are formed and maintained by the dissipative processes that exchange energy between the system and its environment, and because they disappear if that exchange ceases. It may be said they live in symbiosis with their environment. Energy transformations in biology are primarily dependent on photosynthesis
. The total energy captured by photosynthesis in green plants from the solar radiation is about 2 x 1023 joules of energy per year. Annual energy captured by photosynthesis in green plants is about 4% of the total sunlight
energy which reaches Earth. The energy transformations in biological communities surrounding hydrothermal vent
s are exceptions; they oxidize sulfur
, obtaining their energy via chemosynthesis
rather than photosynthesis.
in biology
and biochemistry
. Principles covered include the first law of thermodynamics
, the second law of thermodynamics
, Gibbs free energy
, statistical thermodynamics, reaction kinetics, and on hypotheses of the origin of life. Presently, biological thermodynamics concerns itself with the study of internal biochemical dynamics as: ATP hydrolysis, protein stability, DNA binding, membrane diffusion, enzyme kinetics, and other such essential energy controlled pathways. Thermodynamically, the amount of energy capable of doing work during a chemical reaction is measured quantitatively by the change in the Gibbs free energy
. The physical biologist Alfred Lotka attempted to unify the change in the Gibbs free energy with evolutionary theory.
arises. Hess’s Law states that the heat absorbed or evolved in a given reaction must always be constant and independent of the manner in which the reaction takes place. Although some intermediate reactions may be endothermic and others may be exothermic, the total heat exchange is equal to the heat exchange had the process occurred directly. This principle is the basis for the calorimeter
, a device used to determine the amount of heat in a chemical reaction. Since all incoming energy enters the body as food and is ultimately oxidized, the total heat production may be estimated by measuring the heat produced by the oxidation of food in a calorimeter. This heat is expressed in kilocalories, which are the common unit of food energy found on nutrition labels.
and boundaries. A living organism is an open system, able to exchange both matter and energy with its environment. Take, for example, the assembly of a virus molecule from its subunits, which clearly involves an increase of order. If the virus is considered an isolated system, this process would be in defiance of the Second Law. However, a virus molecule interacts directly with its environment. The assembly of a virus molecule results in an increase of entropy in the system as a whole due to the liberation of water of solvation
from the components and the resulting increase in rotational and translational entropy of the solvent.
where:
The change in Gibbs Free Energy can be used to determine whether a given chemical reaction can occur spontaneously. If ∆G is negative, the reaction can occur spontaneously
. Likewise, if ∆G is positive, the reaction is nonspontaneous. Chemical reactions can be “coupled” together if they share intermediates. In this case, the overall Gibbs Free Energy change is simply the sum of the ∆G values for each reaction. Therefore, an unfavorable reaction (positive ∆G1) can be driven by a second, highly favorable reaction (negative ∆G2 where the magnitude of ∆G2 > magnitude of ∆G1). For example, the reaction of glucose with fructose to form sucrose has a ∆G value of +5.5 kcal/mole. Therefore, this reaction will not occur spontaneously. The breakdown of ATP to form ADP and inorganic phosphate has a ∆G value of -7.3 kcal/mole. These two reactions can be coupled together, so that glucose binds with ATP to form glucose-1-phosphate and ADP. The glucose-1-phosphate is then able to bond with fructose yielding sucrose and inorganic phosphate. The ∆G value of the coupled reaction is -1.8 kcal/mole, indicating that the reaction will occur spontaneously. This principle of coupling reactions to alter the change in Gibbs Free Energy is the basic principle behind all enzymatic action in biological organisms.
Bioenergetics
Bioenergetics is the subject of a field of biochemistry that concerns energy flow through living systems. This is an active area of biological research that includes the study of thousands of different cellular processes such as cellular respiration and the many other metabolic processes that can...
, the study of energy transformation in the biological sciences. Biological thermodynamics may be defined as the quantitative study of the energy transductions that occur in and between living organisms, structures, and cells and of the nature and function of the chemical processes underlying these transductions. Biological thermodynamics may address the question of whether the benefit associated with any particular phenotypic
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
trait is worth the energy investment it requires.
History
German-British medical doctor and biochemist Hans KrebsHans Adolf Krebs
Sir Hans Adolf Krebs was a German-born British physician and biochemist. Krebs is best known for his identification of two important metabolic cycles: the urea cycle and the citric acid cycle...
' 1957 book Energy Transformations in Living Matter (written with Hans Kornberg
Hans Kornberg
Professor Sir Hans Leo Kornberg, FRS is a British biochemist.-Early Life, Education and Career:Kornberg was born in 1928 in Germany of Jewish parents. In 1939 he left Nazi Germany , and moved to the care of an uncle in Yorkshire...
) was the first major publication on the thermodynamics of biochemical reactions. In addition, the appendix contained the first-ever published thermodynamic tables, written by K. Burton, to contain equilibrium constants and Gibbs free energy
Gibbs free energy
In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a thermodynamic system at a constant temperature and pressure...
of formations for chemical species, able to calculate biochemical reactions that had not yet occurred.
Non-equilibrium thermodynamics
Non-equilibrium thermodynamics
Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium; for they are changing or can be triggered to change over time, and are continuously and discontinuously...
has been applied for explaining how biological organisms can develop from disorder. Ilya Prigogine
Ilya Prigogine
Ilya, Viscount Prigogine was a Russian-born naturalized Belgian physical chemist and Nobel Laureate noted for his work on dissipative structures, complex systems, and irreversibility.-Biography :...
developed methods for the thermodynamic treatment of such systems. He called these systems dissipative systems, because they are formed and maintained by the dissipative processes that exchange energy between the system and its environment, and because they disappear if that exchange ceases. It may be said they live in symbiosis with their environment. Energy transformations in biology are primarily dependent on photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. The total energy captured by photosynthesis in green plants from the solar radiation is about 2 x 1023 joules of energy per year. Annual energy captured by photosynthesis in green plants is about 4% of the total sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
energy which reaches Earth. The energy transformations in biological communities surrounding hydrothermal vent
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
s are exceptions; they oxidize sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
, obtaining their energy via chemosynthesis
Chemosynthesis
In biochemistry, chemosynthesis is the biological conversion of one or more carbon molecules and nutrients into organic matter using the oxidation of inorganic molecules or methane as a source of energy, rather than sunlight, as in photosynthesis...
rather than photosynthesis.
The focus of thermodynamics in biology
The field of biological thermodynamics is focused on principles of chemical thermodynamicsChemical thermodynamics
Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics...
in biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
and biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
. Principles covered include the first law of thermodynamics
First law of thermodynamics
The first law of thermodynamics is an expression of the principle of conservation of work.The law states that energy can be transformed, i.e. changed from one form to another, but cannot be created nor destroyed...
, the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...
, Gibbs free energy
Gibbs free energy
In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a thermodynamic system at a constant temperature and pressure...
, statistical thermodynamics, reaction kinetics, and on hypotheses of the origin of life. Presently, biological thermodynamics concerns itself with the study of internal biochemical dynamics as: ATP hydrolysis, protein stability, DNA binding, membrane diffusion, enzyme kinetics, and other such essential energy controlled pathways. Thermodynamically, the amount of energy capable of doing work during a chemical reaction is measured quantitatively by the change in the Gibbs free energy
Gibbs free energy
In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a thermodynamic system at a constant temperature and pressure...
. The physical biologist Alfred Lotka attempted to unify the change in the Gibbs free energy with evolutionary theory.
First Law of Thermodynamics
The First Law of Thermodynamics is a statement of the conservation of energy; though it can be changed from one form to another, energy can neither be created nor destroyed. From the first law, a principle called Hess's LawHess's law
Hess' law is a relationship in physical chemistry named for Germain Hess, a Swiss-born Russian chemist and physician.The law states that the enthalpy change for a reaction that is carried out in a series of steps is equal to the sum of the enthalpy changes for the individual steps.The law is an...
arises. Hess’s Law states that the heat absorbed or evolved in a given reaction must always be constant and independent of the manner in which the reaction takes place. Although some intermediate reactions may be endothermic and others may be exothermic, the total heat exchange is equal to the heat exchange had the process occurred directly. This principle is the basis for the calorimeter
Calorimeter
A calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common...
, a device used to determine the amount of heat in a chemical reaction. Since all incoming energy enters the body as food and is ultimately oxidized, the total heat production may be estimated by measuring the heat produced by the oxidation of food in a calorimeter. This heat is expressed in kilocalories, which are the common unit of food energy found on nutrition labels.
Second Law of Thermodynamics
The Second Law of Thermodynamics is primarily concerned with whether or not a given process is possible. The Second Law states that no natural process can occur unless it is accompanied by an increase in the entropy of the universe. Stated differently, an isolated system will always tend to disorder. Living organisms are often mistakenly believed to defy the Second Law because they are able to increase their level of organization. To correct this misinterpretation, only must simply refer to the definition of systemsThermodynamic system
A thermodynamic system is a precisely defined macroscopic region of the universe, often called a physical system, that is studied using the principles of thermodynamics....
and boundaries. A living organism is an open system, able to exchange both matter and energy with its environment. Take, for example, the assembly of a virus molecule from its subunits, which clearly involves an increase of order. If the virus is considered an isolated system, this process would be in defiance of the Second Law. However, a virus molecule interacts directly with its environment. The assembly of a virus molecule results in an increase of entropy in the system as a whole due to the liberation of water of solvation
Solvation
Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...
from the components and the resulting increase in rotational and translational entropy of the solvent.
Gibbs Free Energy
In biological systems, energy and entropy generally change together. Therefore, it is necessary to be able to define a state function which accounts for these changes simultaneously. This state function is the Gibbs Free Energy, G.- G = H − TS
where:
- H is the enthalpyEnthalpyEnthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...
(SI unit: joule) - T is the temperatureTemperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
(SI unit: kelvinKelvinThe kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
) - S is the entropy (SI unit: joule per kelvin)
The change in Gibbs Free Energy can be used to determine whether a given chemical reaction can occur spontaneously. If ∆G is negative, the reaction can occur spontaneously
Spontaneous process
A spontaneous process is the time-evolution of a system in which it releases free energy and moves to a lower, more thermodynamically stable energy state...
. Likewise, if ∆G is positive, the reaction is nonspontaneous. Chemical reactions can be “coupled” together if they share intermediates. In this case, the overall Gibbs Free Energy change is simply the sum of the ∆G values for each reaction. Therefore, an unfavorable reaction (positive ∆G1) can be driven by a second, highly favorable reaction (negative ∆G2 where the magnitude of ∆G2 > magnitude of ∆G1). For example, the reaction of glucose with fructose to form sucrose has a ∆G value of +5.5 kcal/mole. Therefore, this reaction will not occur spontaneously. The breakdown of ATP to form ADP and inorganic phosphate has a ∆G value of -7.3 kcal/mole. These two reactions can be coupled together, so that glucose binds with ATP to form glucose-1-phosphate and ADP. The glucose-1-phosphate is then able to bond with fructose yielding sucrose and inorganic phosphate. The ∆G value of the coupled reaction is -1.8 kcal/mole, indicating that the reaction will occur spontaneously. This principle of coupling reactions to alter the change in Gibbs Free Energy is the basic principle behind all enzymatic action in biological organisms.
See also
- BioenergeticsBioenergeticsBioenergetics is the subject of a field of biochemistry that concerns energy flow through living systems. This is an active area of biological research that includes the study of thousands of different cellular processes such as cellular respiration and the many other metabolic processes that can...
- Ecological energeticsEcological energeticsEcological energetics is the quantitative study of the flow of energy through ecological systems. It aims to uncover the principles which describe the propensity of such energy flows through the trophic, or 'energy availing' levels of ecological networks. In systems ecology the principles of...
- Harris-Benedict Equations
Further reading
- Haynie, D. (2001). Biological Thermodynamics (textbook). Cambridge: Cambridge University Press.
- Lehninger, A., Nelson, D., & Cox, M. (1993). Principles of Biochemistry, 2nd Ed (textbook). New York: Worth Publishers.
- Alberty, Robert, A. (2006). Biochemical Thermodynamics: Applications of Mathematica (Methods of Biochemical Analysis), Wiley-Interscience.
External links
- Cellular Thermodynamics - Wolfe, J. (2002), Encyclopedia of Life Sciences.
- Bioenergetics