chemical reactions

(noun)

Processes that lead to the transformation of one set of chemical substances to another.

Related Terms

Examples of chemical reactions in the following topics:

  • Enzymes Used in Industry

    • Enzymes are biological molecules that catalyze (increase the rates of) chemical reactions.
    • Enzymes are biological molecules that catalyze (increase the rates of) chemical reactions.
    • Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life.
    • Activity is also affected by temperature, pressure, chemical environment (e.g., pH), and substrate concentration.
    • Enzymes are used in the chemical industry and other industrial applications when extremely specific catalysts are required.

  • Habitats and Energy Metabolism of Crenarchaeota

    • Crenarchaeota exist in a wide range of habitats and exhibit a great variety of chemical reactions in their metabolism.
    • Archaea exhibit a great variety of chemical reactions in their metabolism and use many sources of energy.
    • In these reactions one compound passes electrons to another (in a redox reaction), releasing energy to fuel the cell's activities.
    • These reactions are common in gut-dwelling archaea.
    • Phototrophic archaea use light to produce chemical energy in the form of ATP.

  • Oxygenic Photosynthesis

    • Carbon fixation is a redox reaction, so photosynthesis needs to supply both a source of energy to drive this process, and the electrons needed to convert carbon dioxide into a carbohydrate, which is a reduction reaction.
    • In general outline, photosynthesis is the opposite of cellular respiration, where glucose and other compounds are oxidized to produce carbon dioxide, water, and release chemical energy.
    • However, the two processes take place through a different sequence of chemical reactions and in different cellular compartments.The general equation for photosynthesis is therefore:2n CO2 + 2n DH2 + photons → 2(CH2O)n + 2n DOCarbon dioxide + electron donor + light energy → carbohydrate + oxidized electron donor.In oxygenic photosynthesis water is the electron donor and, since its hydrolysis releases oxygen, the equation for this process is:2n CO2 + 4n H2O + photons → 2(CH2O)n + 2n O2 + 2n H2Ocarbon dioxide + water + light energy → carbohydrate + oxygen + waterOften 2n water molecules are cancelled on both sides, yielding:2n CO2 + 2n H2O + photons → 2(CH2O)n + 2n O2carbon dioxide + water + light energy → carbohydrate + oxygen
    • Photosynthesis changes sunlight into chemical energy, splits water to liberate O2, and fixes CO2 into sugar.

  • Anoxygenic Photosynthesis

    • Photosynthetic reactions can be anoxygenic, thus they do not produce oxygen.
    • Phototrophy is the process by which organisms trap light energy (photons) and store it as chemical energy in the form of ATP and/or reducing power in NADPH.
    • Oxygenic and anoxygenic photosynthesizing organisms undergo different reactions either in the presence of light or with no direct contribution of light to the chemical reaction (colloquially called "light reactions" and "dark reactions", respectively).
    • The electron transport chain of purple non-sulfur bacteria begins when the reaction centre bacteriochlorophyll pair, P870, becomes excited from the absorption of light.
    • The electron returns to P870 at the end of the chain so it can be used again once light excites the reaction-center.

  • Synthesizing DNA

    • This occurs in two fashions, by polymerase chain reaction (PCR) which is enzymatic and chemical synthesis.
    • Here we will focus on chemical synthesis of DNA, which is also known as oligonucleotide synthesis.
    • Oligonucleotide synthesis is the chemical synthesis of relatively short fragments of nucleic acids, both DNA and RNA with a defined chemical structure (sequence).
    • The occurrence of side reactions sets practical limits for the length of synthetic oligonucleotides (up to about 200 nucleotide residues) because the number of errors accumulates with the length of the oligonucleotide being synthesized.
    • The complex chemical reactions that are needed to couple one nucleotide to another are outlined here.

  • Effective Disinfection

    • Those that are used indoors should never be mixed with other cleaning products, or else chemical reactions can occur.
    • Should some bacteria survive a chemical attack, they give rise to new generations composed completely of bacteria that are resistant to the particular chemical used.
    • Under a sustained chemical attack, the surviving bacteria in successive generations are increasingly resistant to the chemical used, and ultimately the chemical is rendered ineffective.
    • For this reason, some question the wisdom of impregnating cloths, cutting boards, and worktops in the home with bactericidal chemicals .
    • Low-level disinfection kills some viruses and bacteria with a chemical germicide registered as a hospital disinfectant by the EPA.

  • Type I (Anaphylactic) Reactions

    • Exercise or temperature (either hot or cold) may also trigger anaphylaxis by causing tissue cells known as mast cells to release chemicals that start the allergic reaction.
    • Anaphylaxis is a severe allergic reaction that starts suddenly and affects many body systems.
    • This release is typically associated with an immune system reaction, but may also be caused by damage to cells that are not related to an immune reaction.
    • When anaphylaxis is not caused by in immune response, the reaction is due to an agent that directly damages mast cells and basophils, causing them to release histamine and other substances that are usually associated with an allergic reaction (degranulation).
    • A representation of the signs and symptoms of anaphylaxis that result from an allergic reaction.

  • Allergic Responses to Drugs

    • An allergic reaction is the body's response to clear a foreign substance.
    • The worst allergic reactions can be very severe and result in anaphylaxis .
    • While the most severe cases can result in anaphylaxis, most reactions are not severe.
    • Additionally the allergic reaction may not even be due to the penicillin, as dyes and other chemicals added to antimicrobial drugs may in fact cause the allergic response instead.
    • In the process of sp3 hybridization in methane, the single 2s and three 2p orbitals of carbon mix into four sp3 hybrid orbitals, which are chemically and geometrically identical.

  • Respiration and Proton Motive Force

    • Chemically, cellular respiration is considered an exothermic redox reaction.
    • Most of these smaller reactions are redox reactions themselves.
    • While the overall reaction is a combustion reaction, no single reaction that comprises it is a combustion reaction.
    • Aerobic reactions require oxygen for ATP generation.
    • The overall reaction can be expressed this way:

  • Inhibiting Essential Metabolite Synthesis

    • An antimetabolite is a chemical that inhibits the use of a metabolite, a chemical that is part of normal metabolism.
    • An antimetabolite is a chemical that inhibits the use of a metabolite, a chemical that is part of normal metabolism.
    • For example, azathioprine is the main immunosuppressive cytotoxic substance that is widely used in transplants to control rejection reactions by inhibiting DNA synthesis in lymphocytes.