Chemistry
Biological Catalyst
A biological catalyst is a substance, typically a protein, that speeds up chemical reactions in living organisms without being consumed in the process. These catalysts, known as enzymes, play a crucial role in various metabolic processes, such as digestion and respiration. By lowering the activation energy required for reactions, biological catalysts enable essential biochemical reactions to occur at a faster rate.
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7 Key excerpts on "Biological Catalyst"
eBook - ePubBioinspiration and Biomimicry in Chemistry
Reverse-Engineering Nature
- Gerhard Swiegers(Author)
- 2012(Publication Date)
- Wiley(Publisher)
Chapter 7: Bioinspired Catalysis Gerhard F. Swiegers, Jun Chen and Pawel Wagner7.1 Introduction
Catalysts are species that accelerate chemical reactions without themselves being consumed in the process. The most efficient catalysts by far are the catalysts of biology, known as enzymes. The maintenance and creation of life in all its many and varied forms on Earth depends on the ability of enzymes to speed chemical transformations in biochemical systems. To this end, enzymes often display truly amazing vigour, specificity, and reliability. The fact that life itself depends on the action of enzymes testifies to their remarkable power.To illustrate enzymatic capacities, it is worth considering that a single example of the enzyme carbonic anhydrase has the capacity to convert 600,000 CO2 molecules per second in our muscles into H2 CO3 in our blood.1, 2 It can do this repeatedly, without fail, at body temperature (37° C) in the extraordinarily mixed reactant feedstock that is a biological fluid, and at a CO2 partial pressure of ≤ 1 atmosphere.1, 2 Moreover, it selectively transforms CO2 in the presence of a wide variety of other possible reagents without becoming deactivated.By comparison, modern industrial catalysts are rudimentary in their operation. For example, the economically important Haber–Bosch process for the production of ammonia from nitrogen and hydrogen typically requires temperatures of 500 °C with the reagent gases compressed to 1000 atmospheres. Despite these extremes, ammonia is generated in only 15–25% yield. The catalyst, a heterogeneous iron and oxide mix, must be replaced periodically because it is poisoned by even miniscule impurities in the feedstocks.How do enzymes achieve such feats? More pertinently, how can we replicate them?Because of the remarkable versatility and efficiency of enzymes, understanding and applying Nature's catalytic principles in nonbiological systems is exceedingly important. Ronald Breslow of Columbia University outlined it as one of the Holy Grails of chemistry in a landmark 1995 scientific publication in the journal Accounts of Chemical Research.3 He coined the term biomimetic chemistry, which is defined as3
- Frederick Bettelheim, William Brown, Mary Campbell, Shawn Farrell(Authors)
- 2019(Publication Date)
- Cengage Learning EMEA(Publisher)
641 CONTENTS 22.1 Enzymes are Biological Catalysts 22.2 Enzyme Nomenclature 22.3 Enzyme Activity 22.4 Enzyme Mechanisms 22.5 Enzyme Regulation 22.6 Enzymes in Medicine Enzymes 22 22.1 Enzymes are Biological Catalysts The cells in your body are chemical factories. Only a few of the thousands of compounds necessary for the human organism are obtained from the diet. Instead, most of these substances are synthesized within the cells, which means that thousands of chemical reactions take place in your cells every second of your life. Nearly all of these reactions are catalyzed by enzymes , which are large molecules that increase the rates of chemical reactions without themselves undergoing any change. Without enzymes to act as Biological Catalysts, life as we know it would not be possible. The vast majority of all known enzymes are globular proteins, and we will devote most of our study to protein-based enzymes. However, pro-teins are not the only Biological Catalysts. Ribozymes are enzymes made of ribonucleic acids. They catalyze the self-cleavage of certain portions of their own molecules and are involved in the reaction that generates pep-tide bonds (Chapter 21). Many biochemists believe that during evolution, RNA catalysts emerged first, with protein enzymes arriving on the scene later. (We will learn more about RNA catalysts in Section 24.4.) Like all catalysts, enzymes do not change the position of equilibrium. That is, enzymes cannot make a reaction take place that would not occur without them. Instead, they increase the reaction rate: they cause reactions © ibreakstock/Shutterstock.com Ribbon diagram of cytochrome c oxidase, the enzyme that directly uses oxygen during respiration. Copyright 2020 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
eBook - PDF- Edward Bittar(Author)
- 1996(Publication Date)
- Elsevier Science(Publisher)
In turn, the ways that these catalysts function are responsible for many of the most fundamental properties of living organisms. These properties also help explain the action of many medicines and drugs (as well as herbicides, pesticides, poisons, and all types of bioreactive molecules), and the phenomenon of 'biological specificity'. It should be stressed that this chapter takes the minimalist attitude about enzymes themselves. That is, it presents the smallest amount of enzymology needed to understand some basic features of biology and medicine. This presentation will briefly outline some of the mechanisms of enzyme catalysis and will spend most of the time describing the ramifications of these mechanisms for more overt biological properties. Enzyme behavior provides a foundation for understanding the mode of action of many of the chemicals used in medicine.
- A. Kayode Coker(Author)
- 2001(Publication Date)
- Gulf Professional Publishing(Publisher)
830 Modeling of Chemical Kinetics and Reactor Design 830 CHAPTER ELEVEN Biochemical Reaction INTRODUCTION The processing of biological materials and employing biological agents such as cells, enzymes, or antibodies are the principal domain of biochemical engineering. Biochemical reactions involve both cellular and enzymatic processes and the principal differences between the biochemical and chemical reactions lie in the nature of the living systems. Small living creatures known as microorganisms interact in many ways with human activities. Microorganisms play a primary role in the capture of energy from the sun. Additionally, their biological activities also complete critical segments of the cycles of carbon, oxygen, nitrogen, and other elements necessary for life. The cell is the unit of life, and cells in multi-cellular organism function together with other specialized cells. Generally, all cells possess basic common features. Every cell contains cytoplasm, a colloidal system of large biochemicals in a complex solution of smaller organic molecules and inorganic salts. The use of cells or enzymes taken from cells is restricted to conditions at which they operate, although most plant and animal cells live at moderate temperatures but cannot tolerate extremes of pH. In contrast, many microorganisms operate under mild con-ditions, some perform at high temperatures, others at low temperatures and also pH values, which exceed neutrality. Some can tolerate con-centrations of chemicals that can be highly toxic in other cells. Thus, successful operation depends on acquiring the correct organisms or enzymes while preventing the entry of foreign organisms, which could impair the process. Some variables such as temperature, pH, nutrient medium, and redox potential are favorable to certain organisms while discouraging the growth of others. The major characteristics of microbial processes that contrast with those of ordinary chemical processing include the following [1]:
eBook - PDF- N.A.M. Eskin(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
In warm-blooded animals the temperature is approximately 37°C and the pH of the tissues is close to neutrality. These are the conditions by which Biological Catalysts have to work, and yet the chemical versatility and ability of the living cell are vastly superior to those which are possible in the chemical laboratory. II. Early Work on Biological Catalysis And Noah began to be an husbandman, and he planted a vineyard: and he drank of the wine, and was drunken. Genesis 9:20-21. The effects of Biological Catalysts have long been exploited in the making of cheese and bread and in the production of alcoholic beverages. Such activities stretch back into the mists of antiquity, but it is only very recently that knowl-edge has been gained into the actual mode of action of processes such as alco-holic fermentation. Van Helmont, who lived in the seventeenth century, considered digestion to be a chemical process. He postulated, with incredible foresight, that diges-tion involved actual chemical transformation of food through the mediation of ferments. This name was derived from the fermentation of wine. A demon-stration of this concept was made by Spallanzani (1729-1799) who fed hawks with pieces of meat enclosed in wire cages, which subsequently were regurgi-tated. This experiment provided evidence that gastric juice contained a prin-ciple which liquefied meat. Kirchhoff in 1814 demonstrated that starch could be converted into sugar by wheat extract. Payen and Persoz in 1833 found that an ethanolic precipitate of malt extract contained a thermolabile substance which was capable of converting starch to sugar, the substance being named diastase. A similar activity was later found in saliva. Pasteur in 1860 carried out a series of experiments from which he concluded that alcoholic fermenta-tion takes place only in the presence of living yeast cells. On the other hand, Liebig postulated that processes such as fermentation were purely chemical reactions.
eBook - PDF- P Karlson(Author)
- 1975(Publication Date)
- Academic Press(Publisher)
Enzymes have been called catalysts or, loosely speaking, accelerators of reactions. In order to understand their action we must first ask why chemical reactions really take place. 2. Chemical Equilibria and Chemical Energetics Equilibria of Chemical Reactions. A large number of chemical and biochemical reactions attain a measurable equilibrium among their reactants. Two well-known examples are given here : CH3COOH ^ C H 3 C 0 0 ® + H® ( 1 ) CH3COOH + C 2 H 5 O H ^ C H 3 C O O C 2 H 5 + H O H (2) General chemistry teaches that the law of mass action applies to equilibria. For reaction (1) it may be formulated as follows: Q : H 3 c o o e x C H® _ £ Q : H 3 C O O H 1 The apoenzyme, the protein itself, has also been called a colloidal carrier. This terminology is based largely on Willstätter's idea that the molecule of an enzyme consists of a colloidal carrier and an active group with purely chemical activity. In Willstätter's time (around 1920) this statement nevertheless represented scientific progress, because it identified the action of enzymes with chemical properties. Today the concept of a colloidal carrier must be rejected, because it implies that the protein component is inactive, and we now know that it is not. The group with purely chemical activity is now designated the active site of the enzyme protein. 76 V . E N Z Y M E S A N D B I O C A T A L Y S I S Here, C CH3COOH , C C H 3 c o o e » a n d C H $ stand for the concentrations (in moles per liter) of the reactants as they are found when equilibrium is established. In the case of the dissociation of acetic acid the equilibrium is established nearly instantaneously; the ester formation of reaction (2), for which we can write an ana-logous concentration equation, takes more time to reach equilibrium. Finally, the state of equilibrium can be attained from either side of the reaction, i.e., from a mixture of acetic acid and alcohol as well as from ethyl acetate and water.
eBook - PDF- P Karlson(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Thermodynamically, catalysts lower the necessary energy of activation of the reaction and thus facilitate reaching equilibrium. Enzymes achieve this according to the principle of intermediary catalysis: initially an enzyme-substrate complex, ES, is formed which, in the reaction proper, becomes a complex of enzyme and product, EP. The latter complex then dissociates into enzyme + product, whereby the enzyme is regenerated and free to 4 The change in enthalpy differs from change of heat content (developed or absorbed quantity of heat) only by its sign: AH = —Q p -5 Entropy is a measure of the lack of molecular order. According to Boltzmann, entropy is a measure of the probability of a state: S = k · In W. Disordered states always are more probable than ordered ones. Entropy is expressed in cal/°K or entropy units; the dimension of Τ· AS thus becomes cal, or the dimen-sion of energy. 6 For an introduction to biochemical thermodynamics, see I. M. Klotz, Energy Changes in Biochemical Reactions. Academic Press, New York, 1967. 3. CATALYSTS AND ENZYMES 79 Fig. V -2. Energy of activation and the function of catalysts. associate with another substrate molecule. The energy of activation of each of these steps is considerably smaller than it is for the overall noncatalyzed reaction (cf. Fig. V-2b). The catalyzed reaction therefore proceeds much faster. The net amount of free energy (AG) remains unchanged in the process, and as a result the equilibrium position also remains the same. Catalysis beyond the state of equilibrium, i.e., a shift of equilibrium, is not possible, however. Every reaction, though catalyzed by an enzyme, proceeds only until equilibrium is reached. This same equilibrium would have been reached in the presence of some inorganic catalyst, or even without the aid of a catalyst; the equilibrium is defined alone by the equilibrium constant K. 1 This fundamental law of the action of enzyme must never be forgotten.
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