Lactic acid

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Lactic_acid

Lactic acid is an organic acid. It has a molecular formula CH₃CH(OH)COOH. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate (or the lactate anion). The name of the derived acyl group is lactoyl.

In solution, it can ionize by loss of a proton to produce the lactate ion CH
₃CH(OH)CO⁻
₂. Compared to acetic acid, its pK_a is 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.

Lactic acid is chiral, consisting of two enantiomers. One is known as L-lactic acid, (S)-lactic acid, or (+)-lactic acid, and the other, its mirror image, is D-lactic acid, (R)-lactic acid, or (−)-lactic acid. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid. Lactic acid is hygroscopic. DL-Lactic acid is miscible with water and with ethanol above its melting point, which is about 16 to 18 °C (61 to 64 °F). D-Lactic acid and L-lactic acid have a higher melting point. Lactic acid produced by fermentation of milk is often racemic, although certain species of bacteria produce solely D-lactic acid. On the other hand, lactic acid produced by anaerobic respiration in animal muscles has the (L) enantiomer and is sometimes called "sarcolactic" acid, from the Greek sarx, meaning "flesh".

In animals, L-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. The concentration of blood lactate is usually 1–2 mMTooltip millimolar at rest, but can rise to over 20 mM during intense exertion and as high as 25 mM afterward. In addition to other biological roles, L-lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA₁), which is a G_i/o-coupled G protein-coupled receptor (GPCR).

In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as caries. In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution. These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.

History

Swedish chemist Carl Wilhelm Scheele was the first person to isolate lactic acid in 1780 from sour milk. The name reflects the lact- combining form derived from the Latin word lac, meaning "milk". In 1808, Jöns Jacob Berzelius discovered that lactic acid (actually L-lactate) also is produced in muscles during exertion. Its structure was established by Johannes Wislicenus in 1873.

In 1856, the role of Lactobacillus in the synthesis of lactic acid was discovered by Louis Pasteur. This pathway was used commercially by the German pharmacy Boehringer Ingelheim in 1895.

In 2006, global production of lactic acid reached 275,000 tonnes with an average annual growth of 10%.

Production

Lactic acid is produced industrially by bacterial fermentation of carbohydrates, or by chemical synthesis from acetaldehyde. As of 2009, lactic acid was produced predominantly (70–90%) by fermentation. Production of racemic lactic acid consisting of a 1:1 mixture of D and L stereoisomers, or of mixtures with up to 99.9% L-lactic acid, is possible by microbial fermentation. Industrial scale production of D-lactic acid by fermentation is possible, but much more challenging.

Fermentative production

Fermented milk products are obtained industrially by fermentation of milk or whey by Lactobacillus bacteria: Lactobacillus acidophilus, Lacticaseibacillus casei (Lactobacillus casei), Lactobacillus delbrueckii subsp. bulgaricus (Lactobacillus bulgaricus), Lactobacillus helveticus, Lactococcus lactis , Bacillus amyloliquefaciens, and Streptococcus salivarius subsp. thermophilus (Streptococcus thermophilus).

As a starting material for industrial production of lactic acid, almost any carbohydrate source containing C
₅ (Pentose sugar) and C
₆ (Hexose sugar) can be used. Pure sucrose, glucose from starch, raw sugar, and beet juice are frequently used. Lactic acid producing bacteria can be divided in two classes: homofermentative bacteria like Lactobacillus casei and Lactococcus lactis, producing two moles of lactate from one mole of glucose, and heterofermentative species producing one mole of lactate from one mole of glucose as well as carbon dioxide and acetic acid/ethanol.

Chemical production

Racemic lactic acid is synthesized industrially by reacting acetaldehyde with hydrogen cyanide and hydrolysing the resultant lactonitrile. When hydrolysis is performed by hydrochloric acid, ammonium chloride forms as a by-product; the Japanese company Musashino is one of the last big manufacturers of lactic acid by this route. Synthesis of both racemic and enantiopure lactic acids is also possible from other starting materials (vinyl acetate, glycerol, etc.) by application of catalytic procedures.

Biology

Molecular biology

L-Lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA₁), a G_i/o-coupled G protein-coupled receptor (GPCR).

Exercise and lactate

See also: N-Lactoylphenylalanine

During power exercises such as sprinting, when the rate of demand for energy is high, glucose is broken down and oxidized to pyruvate, and lactate is then produced from the pyruvate faster than the body can process it, causing lactate concentrations to rise. The production of lactate is beneficial for NAD⁺ regeneration (pyruvate is reduced to lactate while NADH is oxidized to NAD⁺), which is used up in oxidation of glyceraldehyde 3-phosphate during production of pyruvate from glucose, and this ensures that energy production is maintained and exercise can continue. During intense exercise, the respiratory chain cannot keep up with the amount of hydrogen ions that join to form NADH, and cannot regenerate NAD⁺ quickly enough.

The resulting lactate can be used in two ways:

• Oxidation back to pyruvate by well-oxygenated muscle cells, heart cells, and brain cells
  • Pyruvate is then directly used to fuel the Krebs cycle
• Conversion to glucose via gluconeogenesis in the liver and release back into circulation; see Cori cycle
  • If blood glucose concentrations are high, the glucose can be used to build up the liver's glycogen stores.

However, lactate is continually formed at rest and during all exercise intensities. Lactate serves as a metabolic fuel being produced and oxidatively disposed in resting and exercising muscle. Some causes of this are metabolism in red blood cells that lack mitochondria, and limitations resulting from the enzyme activity that occurs in muscle fibers having high glycolytic capacity. Lactic acidosis is a physiological condition characterized by accumulation of lactate (especially L-lactate), with formation of an excessively low pH in the tissues – a form of metabolic acidosis.

Lactic acidosis during exercise may occur due to the H⁺ from ATP hydrolysis (ATP⁴⁻ + H₂O → ADP³⁻ + HPO²⁻
₄ + H⁺), and that reducing pyruvate to lactate (pyruvate⁻ + NADH + H⁺ → lactate⁻ + NAD⁺) actually consumes H⁺. The causative factors of the increase in [H⁺] result from the production of lactate⁻ from a neutral molecule, increasing [H⁺] to maintain electroneutrality. A contrary view is that lactate⁻ is produced from pyruvate⁻, which has the same charge. It is pyruvate⁻ production from neutral glucose that generates H⁺:

	C6H12O6 + 2 NAD+ + 2 ADP3− + 2 HPO2− 4	→	2 CH 3COCO− 2 + 2 H+ + 2 NADH + 2 ATP4− + 2 H2O
Subsequent lactate− production absorbs these protons:
	2 CH 3COCO− 2 + 2 H+ + 2 NADH	→	2 CH 3CH(OH)CO− 2 + 2 NAD+
Overall:
	C6H12O6 + 2 NAD+ + 2 ADP3− + 2 HPO2− 4	→	2 CH 3COCO− 2 + 2 H+ + 2 NADH + 2 ATP4− + 2 H2O
		→	2 CH 3CH(OH)CO− 2 + 2 NAD+ + 2 ATP4− + 2 H2O

Although the reaction glucose → 2 lactate⁻ + 2 H⁺ releases two H⁺ when viewed on its own, the H⁺ are absorbed in the production of ATP. On the other hand, the absorbed acidity is released during subsequent hydrolysis of ATP: ATP⁴⁻ + H₂O → ADP³⁻ + HPO²⁻
₄ + H⁺. So once the use of ATP is included, the overall reaction is

C₆H₁₂O₆ → 2 CH
₃COCO⁻
₂ + 2 H⁺

The generation of CO₂ during respiration also causes an increase in [H⁺].

Neural tissue energy source

Although glucose is usually assumed to be the main energy source for living tissues, there are a few reports that indicate that it is lactate, and not glucose, that is preferentially metabolized by neurons in the brain of several mammalian species (the notable ones being mice, rats, and humans). According to the lactate-shuttle hypothesis, glial cells are responsible for transforming glucose into lactate, and for providing lactate to the neurons. Because of this local metabolic activity of glial cells, the extracellular fluid immediately surrounding neurons strongly differs in composition from the blood or cerebrospinal fluid, being much richer with lactate, as was found in microdialysis studies.

Brain development metabolism

Some evidence suggests that lactate is important at early stages of development for brain metabolism in prenatal and early postnatal subjects, with lactate at these stages having higher concentrations in body liquids, and being utilized by the brain preferentially over glucose. It was also hypothesized that lactate may exert a strong action over GABAergic networks in the developing brain, making them more inhibitory than it was previously assumed, acting either through better support of metabolites, or alterations in base intracellular pH levels, or both.

Studies of brain slices of mice show that β-hydroxybutyrate, lactate, and pyruvate act as oxidative energy substrates, causing an increase in the NAD(P)H oxidation phase, that glucose was insufficient as an energy carrier during intense synaptic activity and, finally, that lactate can be an efficient energy substrate capable of sustaining and enhancing brain aerobic energy metabolism in vitro. The study "provides novel data on biphasic NAD(P)H fluorescence transients, an important physiological response to neural activation that has been reproduced in many studies and that is believed to originate predominantly from activity-induced concentration changes to the cellular NADH pools."

Lactate can also serve as an important source of energy for other organs, including the heart and liver. During physical activity, up to 60% of the heart muscle's energy turnover rate derives from lactate oxidation.

Blood testing

Reference ranges for blood tests, comparing lactate content (shown in violet at center-right) to other constituents in human blood

Blood tests for lactate are performed to determine the status of the acid base homeostasis in the body. Blood sampling for this purpose is often arterial (even if it is more difficult than venipuncture), because lactate levels differ substantially between arterial and venous, and the arterial level is more representative for this purpose.

Reference ranges

	Lower limit	Upper limit	Unit
Venous	4.5	19.8	mg/dL
	0.5	2.2	mmol/L
Arterial	4.5	14.4	mg/dL
	0.5	1.6	mmol/L

During childbirth, lactate levels in the fetus can be quantified by fetal scalp blood testing.

Uses

Polymer precursor

Main article: polylactic acid

Two molecules of lactic acid can be dehydrated to the lactone lactide. In the presence of catalysts lactide polymerize to either atactic or syndiotactic polylactide (PLA), which are biodegradable polyesters. PLA is an example of a plastic that is not derived from petrochemicals.

Pharmaceutical and cosmetic applications

Lactic acid is also employed in pharmaceutical technology to produce water-soluble lactates from otherwise-insoluble active ingredients. It finds further use in topical preparations and cosmetics to adjust acidity and for its disinfectant and keratolytic properties.

Lactic acid containing bacteria have shown promise in reducing oxaluria with its descaling properties on calcium compounds.^[39]

Foods

Fermented food

Lactic acid is found primarily in sour milk products, such as kumis, laban, yogurt, kefir, and some cottage cheeses. The casein in fermented milk is coagulated (curdled) by lactic acid. Lactic acid is also responsible for the sour flavor of sourdough bread.

In lists of nutritional information lactic acid might be included under the term "carbohydrate" (or "carbohydrate by difference") because this often includes everything other than water, protein, fat, ash, and ethanol. If this is the case then the calculated food energy may use the standard 4 kilocalories (17 kJ) per gram that is often used for all carbohydrates. But in some cases lactic acid is ignored in the calculation. The energy density of lactic acid is 362 kilocalories (1,510 kJ) per 100 g.

Some beers (sour beer) purposely contain lactic acid, one such type being Belgian lambics. Most commonly, this is produced naturally by various strains of bacteria. These bacteria ferment sugars into acids, unlike the yeast that ferment sugar into ethanol. After cooling the wort, yeast and bacteria are allowed to "fall" into the open fermenters. Brewers of more common beer styles would ensure that no such bacteria are allowed to enter the fermenter. Other sour styles of beer include Berliner weisse, Flanders red and American wild ale.

In winemaking, a bacterial process, natural or controlled, is often used to convert the naturally present malic acid to lactic acid, to reduce the sharpness and for other flavor-related reasons. This malolactic fermentation is undertaken by lactic acid bacteria.

While not normally found in significant quantities in fruit, lactic acid is the primary organic acid in akebia fruit, making up 2.12% of the juice.

Separately added

As a food additive it is approved for use in the EU, United States and Australia and New Zealand; it is listed by its INS number 270 or as E number E270. Lactic acid is used as a food preservative, curing agent, and flavoring agent. It is an ingredient in processed foods and is used as a decontaminant during meat processing. Lactic acid is produced commercially by fermentation of carbohydrates such as glucose, sucrose, or lactose, or by chemical synthesis. Carbohydrate sources include corn, beets, and cane sugar.

Forgery

Lactic acid has historically been used to assist with the erasure of inks from official papers to be modified during forgery.

Cleaning products

Lactic acid is used in some liquid cleaners as a descaling agent for removing hard water deposits such as calcium carbonate, forming the lactate, calcium lactate. Owing to its high acidity, such deposits are eliminated very quickly, especially where boiling water is used, as in kettles. It is used in some antibacterial soaps and dish detergents as a replacement for triclosan.

Electronvolt

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Electronvolt

In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacuum. When used as a unit of energy, the numerical value of 1 eV in joules (symbol J) is equivalent to the numerical value of the charge of an electron in coulombs (symbol C). Under the 2019 redefinition of the SI base units, this sets 1 eV equal to the exact value 1.602176634×10⁻¹⁹ J.

Historically, the electronvolt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because a particle with electric charge q gains an energy E = qV after passing through a voltage of V. Since q must be an integer multiple of the elementary charge e for any isolated particle, the gained energy in units of electronvolts conveniently equals that integer times the voltage.

It is a common unit of energy within physics, widely used in solid state, atomic, nuclear, and particle physics, and high-energy astrophysics. It is commonly used with SI prefixes milli-, kilo-, mega-, giga-, tera-, peta- or exa- (meV, keV, MeV, GeV, TeV, PeV and EeV respectively). In some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion (10⁹) electronvolts; it is equivalent to the GeV.

Definition

An electronvolt is the amount of kinetic energy gained or lost by a single electron accelerating from rest through an electric potential difference of one volt in vacuum. Hence, it has a value of one volt, 1 J/C, multiplied by the elementary charge e = 1.602176634×10⁻¹⁹ C. Therefore, one electronvolt is equal to 1.602176634×10⁻¹⁹ J.

The electronvolt (eV) is a unit of energy, but is not an SI unit. The SI unit of energy is the joule (J).

Relation to other physical properties and units

Measurement	Unit	SI value of unit
Energy	eV	1.602176634×10−19 J
Mass	eV/c2	1.78266192×10−36 kg
Momentum	eV/c	5.34428599×10−28 kg·m/s
Temperature	eV/kB	1.160451812×104 K
Time	ħ/eV	6.582119×10−16 s
Distance	ħc/eV	1.97327×10−7 m

Mass

By mass–energy equivalence, the electronvolt corresponds to a unit of mass. It is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c², where c is the speed of light in vacuum (from E = mc²). It is common to informally express mass in terms of eV as a unit of mass, effectively using a system of natural units with c set to 1. The kilogram equivalent of 1 eV/c² is:

$${\displaystyle 1\text{eV}/c^2=\frac{(1.602176634\times {10}^{-19}\text{C})\times 1\text{V}}{(299792458\mathrm{m}/\mathrm{s}{)}^2}=1.78266192\times {10}^{-36}\text{kg}.}$$

For example, an electron and a positron, each with a mass of 0.511 MeV/c², can annihilate to yield 1.022 MeV of energy. A proton has a mass of 0.938 GeV/c². In general, the masses of all hadrons are of the order of 1 GeV/c², which makes the GeV/c² a convenient unit of mass for particle physics:

1 GeV/c² = 1.78266192×10⁻²⁷ kg.

The atomic mass constant (m_u), one twelfth of the mass a carbon-12 atom, is close to the mass of a proton. To convert to electronvolt mass-equivalent, use the formula:

m_u = 1 Da = 931.4941 MeV/c² = 0.9314941 GeV/c².

Momentum

By dividing a particle's kinetic energy in electronvolts by the fundamental constant c (the speed of light), one can describe the particle's momentum in units of eV/c. In natural units in which the fundamental velocity constant c is numerically 1, the c may informally be omitted to express momentum as electronvolts.

The energy–momentum relation in natural units, ${\displaystyle E^2=p^2+m_0^2}$, is a Pythagorean equation that can be visualized as a right triangle where the total energy ${\displaystyle E}$ is the hypotenuse and the momentum ${\displaystyle p}$ and rest mass ${\displaystyle m_0}$ are the two legs.

The energy momentum relation

$${\displaystyle E^2=p^2{c}^2+m_0^2{c}^4}$$

in natural units (with ${\displaystyle c=1}$)

$${\displaystyle E^2=p^2+m_0^2}$$

is a Pythagorean equation. When a relatively high energy is applied to a particle with relatively low rest mass, it can be approximated as ${\displaystyle E\simeq p}$ in high-energy physics such that an applied energy in units of eV conveniently results in an approximately equivalent change of momentum in units of eV/c.

The dimensions of momentum units are T⁻¹LM. The dimensions of energy units are T⁻²L²M. Dividing the units of energy (such as eV) by a fundamental constant (such as the speed of light) that has units of velocity (T⁻¹L) facilitates the required conversion for using energy units to describe momentum.

For example, if the momentum p of an electron is said to be 1 GeV, then the conversion to MKS system of units can be achieved by:

$${\displaystyle p=1\text{GeV}/c=\frac{(1\times {10}^9)\times (1.602176634\times {10}^{-19}\text{C})\times (1\text{V})}{2.99792458\times {10}^8\text{m}/\text{s}}=5.344286\times {10}^{-19}\text{kg}\cdot \text{m}/\text{s}.}$$

Distance

In particle physics, a system of natural units in which the speed of light in vacuum c and the reduced Planck constant ħ are dimensionless and equal to unity is widely used: c = ħ = 1. In these units, both distances and times are expressed in inverse energy units (while energy and mass are expressed in the same units, see mass–energy equivalence). In particular, particle scattering lengths are often presented in units of inverse particle masses.

Outside this system of units, the conversion factors between electronvolt, second, and nanometer are the following:

${\displaystyle \hslash =1.054571817646\times {10}^{-34}\mathrm{J}\cdot \mathrm{s}=6.582119569509\times {10}^{-16}\mathrm{e}\mathrm{V}\cdot \mathrm{s}.}$

The above relations also allow expressing the mean lifetime τ of an unstable particle (in seconds) in terms of its decay width Γ (in eV) via Γ = ħ/τ. For example, the
B⁰
meson has a lifetime of 1.530(9) picoseconds, mean decay length is cτ = 459.7 μm, or a decay width of (4.302±25)×10⁻⁴ eV.

Conversely, the tiny meson mass differences responsible for meson oscillations are often expressed in the more convenient inverse picoseconds.

Energy in electronvolts is sometimes expressed through the wavelength of light with photons of the same energy:

${\displaystyle \frac{1\text{eV}}{hc}=\frac{1.602176634\times {10}^{-19}\text{J}}{(2.99792458\times {10}^{10}\text{cm}/\text{s})\times (6.62607015\times {10}^{-34}\text{J}\cdot \text{s})}\approx 8065.5439{\text{cm}}^{-1}.}$

Temperature

In certain fields, such as plasma physics, it is convenient to use the electronvolt to express temperature. The electronvolt is divided by the Boltzmann constant to convert to the Kelvin scale:

${\displaystyle 1\text{ eV}/k_{\text{B}}=\frac{1.602176634\times {10}^{-19}\text{ J}}{1.380649\times {10}^{-23}\text{ J/K}}=11604.51812\text{ K},}$

where k_B is the Boltzmann constant.

The k_B is assumed when using the electronvolt to express temperature, for example, a typical magnetic confinement fusion plasma is 15 keV (kiloelectronvolt), which is equal to 174 MK (megakelvin).

As an approximation: k_BT is about 0.025 eV (≈ 290 K/11604 K/eV) at a temperature of 20 °C.

Wavelength

Energy of photons in the visible spectrum in eV

Graph of wavelength (nm) to energy (eV)

The energy E, frequency v, and wavelength λ of a photon are related by

$${\displaystyle E=h\nu =\frac{hc}{\lambda }=\frac{4.135667516\times {10}^{-15}\mathrm{e}\mathrm{V}\cdot \mathrm{s}\times 299792458\mathrm{m}/\mathrm{s}}{\lambda }}$$

where h is the Planck constant, c is the speed of light. This reduces to

$${\displaystyle \begin{array}{rl}E(\mathrm{e}\mathrm{V})& =4.135667516\times {10}^{-15}\mathrm{e}\mathrm{V}\cdot \mathrm{s}\times \nu \\ & =\frac{1239.84193\text{eV}\cdot \text{nm}}{\lambda }.\end{array}}$$

A photon with a wavelength of 532 nm (green light) would have an energy of approximately 2.33 eV. Similarly, 1 eV would correspond to an infrared photon of wavelength 1240 nm or frequency 241.8 THz.

Scattering experiments

In a low-energy nuclear scattering experiment, it is conventional to refer to the nuclear recoil energy in units of eVr, keVr, etc. This distinguishes the nuclear recoil energy from the "electron equivalent" recoil energy (eVee, keVee, etc.) measured by scintillation light. For example, the yield of a phototube is measured in phe/keVee (photoelectrons per keV electron-equivalent energy). The relationship between eV, eVr, and eVee depends on the medium the scattering takes place in, and must be established empirically for each material.

Energy comparisons

Photon frequency vs. energy particle in electronvolts. The energy of a photon varies only with the frequency of the photon, related by speed of light constant. This contrasts with a massive particle of which the energy depends on its velocity and rest mass.

γ: Gamma rays	MIR: Mid infrared	HF: High freq.
HX: Hard X-rays	FIR: Far infrared	MF: Medium freq.
SX: Soft X-rays	Radio waves	LF: Low freq.
EUV: Extreme ultraviolet	EHF: Extremely high freq.	VLF: Very low freq.
NUV: Near ultraviolet	SHF: Super high freq.	VF/ULF: Voice freq.
Visible light	UHF: Ultra high freq.	SLF: Super low freq.
NIR: Near Infrared	VHF: Very high freq.	ELF: Extremely low freq.
		Freq: Frequency

Energy	Source
5.25×1032 eV	total energy released from a 20 kt nuclear fission device
12.2 ReV (1.22×1028 eV)	the Planck energy
10 YeV (1×1025 eV)	approximate grand unification energy
~624 EeV (6.24×1020 eV)	energy consumed by a single 100-watt light bulb in one second (100 W = 100 J/s ≈ 6.24×1020 eV/s)
300 EeV (3×1020 eV = ~50 J)	The first ultra-high-energy cosmic ray particle observed, the so-called Oh-My-God particle.
2 PeV	two petaelectronvolts, the highest-energy neutrino detected by the IceCube neutrino telescope in Antarctica
14 TeV	designed proton center-of-mass collision energy at the Large Hadron Collider (operated at 3.5 TeV since its start on 30 March 2010, reached 13 TeV in May 2015)
1 TeV	a trillion electronvolts, or 1.602×10−7 J, about the kinetic energy of a flying mosquito
172 GeV	rest energy of top quark, the heaviest measured elementary particle
125.1±0.2 GeV	energy corresponding to the mass of the Higgs boson, as measured by two separate detectors at the LHC to a certainty better than 5 sigma
210 MeV	average energy released in fission of one Pu-239 atom
200 MeV	approximate average energy released in nuclear fission fission fragments of one U-235 atom.
105.7 MeV	rest energy of a muon
17.6 MeV	average energy released in the nuclear fusion of deuterium and tritium to form He-4; this is 0.41 PJ per kilogram of product produced
2 MeV	approximate average energy released in a nuclear fission neutron released from one U-235 atom.
1.9 MeV	rest energy of up quark, the lowest mass quark.
1 MeV (1.602×10−13 J)	about twice the rest energy of an electron
1 to 10 keV	approximate thermal temperature, ${\displaystyle k_{\text{B}}T}$, in nuclear fusion systems, like the core of the sun, magnetically confined plasma, inertial confinement and nuclear weapons
13.6 eV	the energy required to ionize atomic hydrogen; molecular bond energies are on the order of 1 eV to 10 eV per bond
1.6 eV to 3.4 eV	the photon energy of visible light
1.1 eV	energy ${\displaystyle E_g}$ required to break a covalent bond in silicon
720 meV	energy ${\displaystyle E_g}$ required to break a covalent bond in germanium
< 120 meV	approximate rest energy of neutrinos (sum of 3 flavors)
25 meV	thermal energy, ${\displaystyle k_{\text{B}}T}$, at room temperature; one air molecule has an average kinetic energy 38 meV
230 μeV	thermal energy, ${\displaystyle k_{\text{B}}T}$, of the cosmic microwave background

Per mole

One mole of particles given 1 eV of energy each has approximately 96.5 kJ of energy – this corresponds to the Faraday constant (F ≈ 96485 C⋅mol⁻¹), where the energy in joules of n moles of particles each with energy E eV is equal to E·F·n.