reaction

(noun)

A transformation in which one or more substances is converted into another by combination or decomposition

Related Terms

  • molecule
  • reactant

Examples of reaction in the following topics:

  • Free Energy

    • How can the energy released from one reaction be compared to that of another reaction?
    • Reactions that have a negative ∆G and, consequently, release free energy, are called exergonic reactions.
    • These chemical reactions are called endergonic reactions; they are non-spontaneous.
    • Therefore, the chemical reactions involved in anabolic processes are endergonic reactions.
    • Exergonic reactions release energy; endergonic reactions require energy to proceed.
  • Activation Energy

    • Cells will at times couple an exergonic reaction $(\Delta G<0)$ with endergonic reactions $(\Delta G>0)$, allowing them to proceed.
    • The free energy released from the exergonic reaction is absorbed by the endergonic reaction.
    • Notice that the activation energy for the reverse reaction is larger than for the forward reaction.
    • A is the frequency factor of the reaction.
    • Activation energy is the energy required for a reaction to proceed; it is lower if the reaction is catalyzed.
  • The Two Parts of Photosynthesis

    • Light-dependent and light-independent reactions are two successive reactions that occur during photosynthesis.
    • Just as the name implies, light-dependent reactions require sunlight.
    • Photosystems consist of a light-harvesting complex and a reaction center.
    • In the light-independent reactions or Calvin cycle, the energized electrons from the light-dependent reactions provide the energy to form carbohydrates from carbon dioxide molecules.
    • Photosynthesis takes place in two stages: light-dependent reactions and the Calvin cycle (light-independent reactions).
  • Hydrolysis

    • During these reactions, the polymer is broken into two components.
    • These reactions are in contrast to dehydration synthesis (also known as condensation) reactions.
    • Dehydration and hydrolysis reactions are chemical reactions that are catalyzed, or "sped up," by specific enzymes; dehydration reactions involve the formation of new bonds, requiring energy, while hydrolysis reactions break bonds and release energy.
    • This is the reverse of the dehydration synthesis reaction joining these two monomers.
    • This is the reverse of the dehydration synthesis reaction joining these two monomers.
  • Enzyme Active Site and Substrate Specificity

    • In some reactions, a single-reactant substrate is broken down into multiple products.
    • Two reactants might also enter a reaction, both become modified, and leave the reaction as two products.
    • This dynamic binding maximizes the enzyme's ability to catalyze its reaction.
    • The enzyme will always return to its original state at the completion of the reaction.
    • After an enzyme is done catalyzing a reaction, it releases its products (substrates).
  • Chemical Reactions and Molecules

    • The equations that describe these reactions contain a unidirectional arrow and are irreversible.
    • Reversible reactions are those that can go in either direction.
    • In biological reactions, however, equilibrium is rarely obtained because the concentrations of the reactants or products or both are constantly changing, often with a product of one reaction being a reactant for another.
    • These reactions are important for maintaining the homeostasis of our blood.
    • Explore reactions in which chemical bonds are formed and broken with this model.
  • ATP: Adenosine Triphosphate

    • Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions to harness the energy within the bonds of ATP.
    • ATP provides the energy for both energy-consuming endergonic reactions and energy-releasing exergonic reactions, which require a small input of activation energy.
    • The reverse reaction combines ADP + Pi to regenerate ATP from ADP.
    • Cells couple the exergonic reaction of ATP hydrolysis with the endergonic reactions of cellular processes.
    • In this example, the exergonic reaction of ATP hydrolysis is coupled with the endergonic reaction of converting glucose for use in the metabolic pathway.
  • Regulatory Mechanisms for Cellular Respiration

    • Some reactions are controlled by having two different enzymes: one each for the two directions of a reversible reaction.
    • Reactions that are catalyzed by only one enzyme can go to equilibrium, stalling the reaction.
    • In contrast, if two different enzymes (each specific for a given direction) are necessary for a reversible reaction, the opportunity to control the rate of the reaction increases and equilibrium is not reached.
    • A number of enzymes involved in each of the pathways (in particular, the enzyme catalyzing the first committed reaction of the pathway) are controlled by attachment of a molecule to an allosteric (non-active) site on the protein.
    • This alteration of the protein's (the enzyme's) structure either increases or decreases its affinity for its substrate, with the effect of increasing or decreasing the rate of the reaction.
  • Control of Metabolism Through Enzyme Regulation

    • A cell's function is encapsulated by the chemical reactions it can carry out.
    • Enzymes lower the activation energies of chemical reactions; in cells, they promote those reactions that are specific to the cell's function.
    • This prevents the enzyme from lowering the activation energy of the reaction, and the reaction rate is reduced.
    • Allosteric activators can increase reaction rates.
    • This increases the reaction rate.
  • Processes of the Light-Dependent Reactions

    • Light-dependent reactions, which take place in photosystem I and II, convert solar energy into NADPH and ATP.
    • The light-dependent reactions begin in photosystem II .
    • That energy is transmitted to the PSI reaction center.
    • The net-reaction of all light-dependent reactions in oxygenic photosynthesis is: 2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP
    • A photosystem consists of a light-harvesting complex and a reaction center.
Subjects
  • Accounting
  • Algebra
  • Art History
  • Biology
  • Business
  • Calculus
  • Chemistry
  • Communications
  • Economics
  • Finance
  • Management
  • Marketing
  • Microbiology
  • Physics
  • Physiology
  • Political Science
  • Psychology
  • Sociology
  • Statistics
  • U.S. History
  • World History
  • Writing

Except where noted, content and user contributions on this site are licensed under CC BY-SA 4.0 with attribution required.