Activation in (bio-)chemical
sciencesScience is in its broadest sense to any systematic knowledge-base or prescriptive practice that is capable of resulting in a prediction or predictable type of outcome...
generally refers to the
processIn science, a process is every sequence of changes of a real object/body which is observable using scientific method. Therefore, all sciences analyze and model processes....
whereby something is prepared or excited for a subsequent
reactionReaction may refer to:*Response to another event*Adverse drug reaction*Chemical reaction*Light reaction*Nuclear reaction*Reaction , as defined by Newton's third law*Reflex reaction*Emotional reaction*Reactionary, a political tendency...
.
In
chemistryChemistry is the science concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical reactions...
, activation of
moleculeA molecule is defined as an electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense...
s is required for a
chemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. They are studied by chemists under a field of science called chemistry. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, often coming about...
to occur. The phrase
energy of activationIn chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur. Arrhenius' research was a follow up of the theories of reaction rate by Serbian physicist Nebojsa...
refers to the energy the reactants must acquire before they can successfully react with each other to produce the
productsA product is a substance that forms as a result of a biological- or chemical reaction. While the end product of some chemical reactions may be the result of a relatively rapid reaction, nanoseconds to seconds, chemical equilibria in complex systems may require years or even centuries to be...
, that is, to reach the
transition stateThe transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate...
. The energy needed for activation can be quite small and the molecules may have enough energy just from thermal fluctuations the molecules naturally have (i.e.
Activation in (bio-)chemical
sciencesScience is in its broadest sense to any systematic knowledge-base or prescriptive practice that is capable of resulting in a prediction or predictable type of outcome...
generally refers to the
processIn science, a process is every sequence of changes of a real object/body which is observable using scientific method. Therefore, all sciences analyze and model processes....
whereby something is prepared or excited for a subsequent
reactionReaction may refer to:*Response to another event*Adverse drug reaction*Chemical reaction*Light reaction*Nuclear reaction*Reaction , as defined by Newton's third law*Reflex reaction*Emotional reaction*Reactionary, a political tendency...
.
Chemistry
In
chemistryChemistry is the science concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical reactions...
, activation of
moleculeA molecule is defined as an electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense...
s is required for a
chemical reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. They are studied by chemists under a field of science called chemistry. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, often coming about...
to occur. The phrase
energy of activationIn chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur. Arrhenius' research was a follow up of the theories of reaction rate by Serbian physicist Nebojsa...
refers to the energy the reactants must acquire before they can successfully react with each other to produce the
productsA product is a substance that forms as a result of a biological- or chemical reaction. While the end product of some chemical reactions may be the result of a relatively rapid reaction, nanoseconds to seconds, chemical equilibria in complex systems may require years or even centuries to be...
, that is, to reach the
transition stateThe transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest energy along this reaction coordinate...
. The energy needed for activation can be quite small and the molecules may have enough energy just from thermal fluctuations the molecules naturally have (i.e. lots of reactions don't have to be heated to proceed). The branch of chemistry that deals with this topic is called
chemical kineticsChemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition...
.
Biochemistry
Similarly,
neutron activationNeutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus often decays immediately by emitting particles such as neutrons, protons, or alpha...
is a standard
analytical techniqueAn analytical technique is a method that is used to determine the concentration of a chemical compound or chemical element. There are a wide variety of techniques used for analysis, from simple weighing to titrations to very advanced techniques using highly specialized instrumentation...
used to analyze for elements, usually,
metalA metal is a chemical element that is a good conductor of both electricity and heat, forms cations and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions...
s. The sample is placed in a high
neutron fluxNeutron flux is a term referring to the number of neutrons passing through an area over a span of time. It is most commonly measured in neutrons/. This is drawn from the mathematical definition of flux...
and in the
nuclear reactionIn nuclear physics and nuclear chemistry, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products different from the initial particles...
involved, a
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
is
capturedNeutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than charged particles which are repelled by electrostatic...
by a
nucleusThe nucleus is the very dense region consisting of nucleons at the center of an atom. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus, with a very small contribution from the orbiting electrons....
. If the resulting new
isotopeIsotopes are different types of atoms of the same chemical element, each having a different number of neutrons. Correspondingly, isotopes differ in mass number but not in atomic number. The difference in the number of nucleons comes from a difference how many neutrons are in the atomic nucleus...
is unstable, it will undergo
radioactive decayRadioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, named the daughter...
. This decay can be monitored and the
elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
emitting identified by the identity and energy of the emitted particles.
Prompt Gamma Activation AnalysisPrompt-gamma neutron activation analysis is a very widely applicable technique for determining the presence and amount of many elements simultaneously in samples ranging in size from micrograms to many grams. It is a non-destructive method, and the chemical form and shape of the sample are...
(PGAA) is a rapid, nondestructive, instrumental, nuclear technique which is used for trace and major component analysis of various elements.
Biology
In
biologyBiology is the natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy...
, activation has the same definition as the definition of activation in
chemistryChemistry is the science concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical reactions...
. However, the activation time of different substrates keep the
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
at check. The activation also protects
cellsThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
from the damage an enzyme might cause to the
bodyWith regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
. A number of enzymes are synthesized as inactive proenzymes. Only when a polypeptide sequence is cleaved from the end of the protein, in a process called activation, is the enzyme brought to its full level of activity. There are two ways that an enzyme can be activated: reversibly and irreversibly. In the irreversible way, a piece of the
proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
is cut off causing the enzyme to stay active. However, in the reversible manner of enzyme activation, a
cofactorCofactor may refer to any of the following:* Cofactor , the signed minor of a matrix* Minor , an alternative name for the determinant of a smaller matrix than that which it describes...
is placed on the enzyme causing it to only stay active until the cofactor stays on. However, when the cofactor is removed, the enzyme stops being active.
Immunology
In
immunologyImmunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with, among other things, the physiological functioning of the immune system in states of both health and disease; malfunctions of the immune system in...
, activation is the transition of leucocytes and other cell types involved in the
immune systemAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumour cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. On the other hand, deactivation is the transition in the reverse direction. This balance is tightly regulated, since a too small degree of activation causes susceptibility to infections, while, on the other hand, a too large degree of activation causes autoimmune diseases.
Activation and deactivation results from a variety of factors, including cytokines, soluble receptors,
arachidonic acidArachidonic acid is an omega-6 fatty acid 20:4.It is the counterpart to the saturated arachidic acid found in peanut oil, Arachidonic acid (AA, sometimes ARA) is an omega-6 fatty acid 20:4(ω-6).It is the counterpart to the saturated arachidic acid found in peanut oil, Arachidonic acid (AA,...
metabolites, steroids, receptor antagonists, adhesion molecules, bacterial products and viral products.
Electrophysiology
Activation refers to the opening of ion channels, i.e. the conformational change that allows ions to pass.