ATP Hydrolysis

7 Key excerpts on "ATP Hydrolysis"

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  eBook - PDF

  Biology 2e

  • Mary Ann Clark, Jung Choi, Matthew Douglas(Authors)
  • 2018(Publication Date)
  • Openstax

    (Publisher)

  Adenosine is a nucleoside consisting of the nitrogenous base adenine and a five-carbon sugar, ribose. The three phosphate groups, in order of closest to furthest from the ribose sugar, are alpha, beta, and gamma. Together, these chemical groups constitute an energy powerhouse. However, not all bonds within this molecule exist in a particularly high-energy state. Both bonds that link the phosphates are equally high-energy bonds ( phosphoanhydride bonds) that, when broken, release sufficient energy to power a variety of cellular reactions and processes. These high-energy bonds are the bonds between the second and third (or beta and gamma) phosphate groups and between the first and second phosphate groups. These bonds are “high-energy” because the products of such bond breaking—adenosine diphosphate (ADP) and one inorganic phosphate group (P i )—have considerably lower free energy than the reactants: ATP and a water molecule. Because this reaction takes place using a water molecule, it is a hydrolysis reaction. In other words, ATP hydrolyzes into ADP in the following reaction: ATP + H 2 O → ADP + P i + free energy Like most chemical reactions, ATP to ADP hydrolysis is reversible. The reverse reaction regenerates ATP from ADP + P i . Cells rely on ATP regeneration just as people rely on regenerating spent money through some sort of income. Since ATP Hydrolysis releases energy, ATP regeneration must require an input of free energy. This equation expresses ATP formation: ADP + P i + free energy → ATP + H 2 O Two prominent questions remain with regard to using ATP as an energy source. Exactly how much free energy releases with ATP Hydrolysis, and how does that free energy do cellular work? The calculated ∆G for the hydrolysis of one ATP mole into ADP and P i is −7.3 kcal/mole (−30.5 kJ/mol). Since this calculation is true under standard conditions, one would expect a different value exists under cellular conditions.

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  Introduction to Nutrition and Metabolism

  • David A Bender, Shauna M C Cunningham(Authors)
  • 2021(Publication Date)
  • CRC Press

    (Publisher)

  chapter three

  The Role of ATP in Metabolism

  Adenosine triphosphate (ATP) acts as the central link between energy-yielding metabolic pathways and energy expenditure in physical and chemical work. The oxidation of metabolic fuels is linked to the phosphorylation of adenosine diphosphate (ADP) to ATP, while the expenditure of metabolic energy for the synthesis of body constituents, transport of compounds across cell membranes and the contraction of muscle results in the hydrolysis of ATP to yield ADP and phosphate ions. The total body content of ATP + ADP is under 350 mmol (about 10 g), but the amount of ATP synthesized and used each day is about 100 mol (about 70 kg), an amount equal to body weight.

  Objectives

  After reading this chapter, you should be able to:

  • explain how endothermic reactions can be linked to the overall hydrolysis of ATP → ADP and phosphate

  • describe how compounds can be transported across cell membranes against a concentration gradient and explain the roles of ATP and proton gradients in active transport

  • describe the role of ATP in muscle contraction and the role of creatine phosphate as a phosphagen

  • describe the structure and functions of the mitochondrion and explain the processes involved in the mitochondrial electron transport chain and oxidative phosphorylation, explain how substrate oxidation is regulated by the availability of ADP, and how respiratory poisons and uncouplers act.

  3.1 Adenine Nucleotides

  Nucleotides consist of a purine or pyrimidine base linked to the 5-carbon sugar ribose. The base plus sugar is a nucleoside; in a nucleotide the sugar is phosphorylated. Nucleotides may be mono-, di- or triphosphates.

  Figure 3.1 The adenine nucleotides (the box shows the structures of adenine, guanine and uracil; guanine and uracil form a similar series of nucleotides).

  Figure 3.1 shows the nucleotides formed from the purine adenine – the adenine nucleotides, adenosine monophosphate (AMP), ADP and ATP. Similar families of nucleotides that are important in metabolism are formed from the guanine and uracil bases (see also Section 10.3.2 for a discussion of the role of cyclic AMP in metabolic regulation and hormone action, and Section 10.3.1

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  Cell Chemistry and Physiology: Part II

  • Edward Bittar(Author)
  • 1996(Publication Date)
  • Elsevier Science

    (Publisher)

  Formation of a peptide bond, for example, is a dehydration: R-COOH + NH2-R' ^ RCO-NH-R' + H2O. The anhydride nature of ATP allows it to be a good dehydrating agent even, given a suitable reaction mechanism (see below), in an aqueous environ-ment. 4. ATP serves as a source of phosphate groups in biochemical reactions. For example, glucose, on entering the cell, is phosphorylated to glucose-6-phos-phate, giving it a negative charge which helps to retain it within a compart-ment bounded by the (lipophilic) cell membrane. Many metabolic pathways (e.g., glycolysis, histidine biosynthesis) utilize phosphorylated intermedi-ates in this way to limit diffusion out of the cell. A contrasting example is the phosphorylation, by ATP, of enzymes such as glycogen phosphorylase which are switched on (or off) by this process. In both these cases, the important feature of ATP is not its tendency to transfer phosphate to water (high negative free energy of hydrolysis) but its tendency to phosphorylate other hydroxyl groups (high phosphate transfer potential). The energetic role of ATP in these phosphorylation reactions is to ensure the reaction is driven to completion; the loss in free energy in generating a phosphate ester in place of an anhydride is dissipated as heat. MEASUREMENT OF CELLULAR ATP The Freeze-Clamp Technique Classically, measurement of ATP levels within cells and tissues has involved (a) the rapid arrest of metabolism and of enzyme activity in the tissue; (b) extraction of ATP from the tissue (without destroying it); and (c) assay of its concentration by enzymatic procedures or by high performance liquid chromatog-raphy (HPLC). Since the energy status of a tissue is also dependent on ADP, AMP, and Pj concentrations, these are generally measured with ATP in a single extract. This technique is highly sensitive; using firefly luciferase (bioluminescent assay) the ATP content of only a few hundred cells can be measured.

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  How Life Works

  The Inside Word from a Biochemist

  • Daphne C. Elliott, William Elliott, Daphne Elliott(Authors)
  • 2015(Publication Date)
  • CSIRO PUBLISHING

    (Publisher)

  The importance of this chemical strategy of incorporating the energy of ATP into energy-requiring chemical reactions cannot be overstated. It might be described as one of the secrets of life. It applies to virtually everything in the body. There are hundreds of different enzymes transferring −P* groups to different molecules. As one example, when you raise your arm −P* groups are transferred from ATP molecules to your muscle proteins where they are then released as −Pi. This supplies the energy for the muscle to contract. The mitochondrial furnaces then immediately spring into action and convert the ADP + −Pi back to ATP again.

  Box 2.3: How ATP drives energy-requiring reactions

  An enzyme transfers a −P* group from ATP to A to give A−P*. A second enzyme now reacts with A−P* and adds B to A, displacing −P* which is released as −Pi (which has zero energy). We can summarise all this very simply as follows:

  1st step: A + ATP → A−P* + ADP (ADP, adenosine diphosphate, is ATP which has lost one phosphate).

  2nd step: A−P* + B → A−B + Pi

  If you put these two reactions together as a summary of the whole process (and it is the whole process which counts so far as the second law is concerned) we get:

  Overall: A + B + ATP → A−B + ADP + Pi

  The energy supplied by ATP breakdown is 30 kJ but only 13 kJ is needed to join A and B together, so the overall process is 17 kJ downhill and will proceed to completion. It is completely in accord with the second law. For some chemical syntheses even more energy is needed, and for these a simple modification is used in the chemical reaction so that two high-energy phosphates are split off the ATP, giving a big energetic kick to the reaction.

  The magnificent concept of life running on high-energy phosphate groups of ATP was put forward in 1941 by Fritz Lipmann working in a laboratory of the Massachusetts General Hospital in Boston, which is part of the Harvard Medical School. Lipmann illustrated his concept as a rotating dynamo with ADP and Pi going in and ATP coming out, the dynamo being driven by food oxidation. It accurately outlined the pattern of energy utilisation of all life forms and his concepts are as true today as they were 50 years ago.

  Lipmann was the archetype of a brilliant scientist totally absorbed in his work. He had an unworldly air, and was liked by all who knew him. When Bill was a member of Lipmann’s laboratory he took lessons at a local driving school and obtained a licence. Lipmann, who had always wanted to learn to drive a car, was very impressed by this and asked him for the phone number of the school. His protective second-in-command, Dave Novelli, quietly said to Bill, ‘For God’s sake don’t give it to him, he’ll kill himself.’ Bill managed to avoid doing so. Lipmann never got a driving licence, but in 1953 he did get a Nobel Prize. His phosphate bond energy concept had, and still has, a tremendous influence on research into the biochemistry of life.

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  Transport And Diffusion Across Cell Membranes

  • Wilfred Stein(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Now, oxygen atoms of the phosphate can be separately labeled with ,6 0, 17 0, and 18 0, and the different reaction products separately identified by nuclear magnetic resonance measurements (see Section 6.2.4.7). Webb and his colleagues (1980) have shown in this way that the mitochondrial 6.4. F^o-ATPases 599 F r ATPase hydrolyzes ATP with an inversion in configuration around the P atom, consistent with a direct displacement of the terminal phosphate by water. In contrast, the calcium-ATPase hydrolyzes ATP with a retention of configuration around the P atom, consistent with the double inversion (the inversion of the inversion) to be expected from the transfer of phosphate first to the enzyme as E—P and then, in a second step, to water (Webb and Trentham, 1981). We saw in Section 6.3.2 that there is convincing evidence for the participation of a phosphoenzyme inter-mediate in the hydrolysis of ATP by the calcium-dependent ATPase. Its mechanism of action and that of the F r ATPase are clearly essentially different! What model will allow us a transport of protons coupled to ATP splitting—a transport of protons that can occur freely when the ATP-splitting system is absent, an ATP splitting that can occur without the proton transport system being present, and a system in which there is no phosphoenzyme intermediate? We have to combine a transport kinetic scheme for the protons (Fig. 6.33a) with a scheme for ATP Hydrolysis (Fig. 6.33b) in such a way that the transport step is not associated with the ATP splitting, but in which coupling can take place. A simple way to do this is to postulate that the form of the enzyme that binds and releases ATP is a protonated species, whereas the form that binds and releases ADP and Pj is a deprotonated form. Protonation and deprotonation of the enzyme, when this is not bound to the organic ligands, can take place only (when Fj and F 0 are combined together) at the outside of the membrane.

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  ATPases

  • A.G. Lee(Author)
  • 1996(Publication Date)
  • Elsevier Science

    (Publisher)

  ATP-DIPHOSPHOHYDROLASES, APYRASES, AND NUCLEOTIDE PHOSPHOHYDROLASES: BIOCHEMICAL PROPERTIES AND FUNCTIONS Adrien R. Beaudoin, Jean Sevigny, and Maryse Richer I. Introduction 370 II. Properties of ATP-diphosphohydrolases (Apyrases) 371 A. Plants 371 B. Invertebrates 373 C. Vertebrates 375 IV. Physiological Roles of ATP-diphosphohydrolases 379 A. Plants 379 B. Invertebrates 380 C. Vertebrates 381 V. Problems Associated with the Identification and Characterization of ATP-Diphosphohydrolases 382 VI. Potential ATP-diphosphohydrolases in Mammalian Tissues 384 A. Bloodvessels 384 B. Heart 385 C. Organs Containing Nonvascular Smooth Muscles 386 Biomembranes Volume 5, pages 369-401. Copyright © 1996 by JAI Press Inc. All rights of reproduction in any form reserved. ISBN: 1-55938-662-2. 369 370 ADRIEN R. BEAUDOIN, JEAN SEVIGNY, and MARYSE RICHER D. Muscles 386 E. Other Organs and Glands 387 F. Nervous System 390 VII. Conclusion 391 Dedication , . 391 Acknowledgments 391 Endnote 391 References 391 I. INTRODUCTION The terms ATP-diphosphohydrolase and apyrase refer to a family of enzymes which split the y- and P-phosphate residues of triphospho- and diphosphonucleosides (Meyerhoff, 1945). Kalckar was the first to describe the properties of apyrases in potato tubers. Indeed, in a paper submitted in January, 1944 to the Journal of Biological Chemistry, he demonstrated that a single enzyme was involved in the hydrolysis of both diphospho- and triphosphonucleosides. In the years that fol-lowed, the potato apyrase was extensively studied, but its function was never clearly demonstrated. It is noteworthy that in Kalckar's studies on potato apyrase, adeny-late kinase was excluded to explain the production of phosphate when ADP was used as the substrate. The latter enzyme can convert two molecules of ADP to ATP and AMP, which could then be degraded by an ATPase and a 5'-nucleotidase, respectively.

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  Survey of Progress in Chemistry

  Volume 1

  • Arthur F. Scott(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  CHEMISTRY OF BIOLOGICAL ENERGY TRANSFER 267 IV. Group Transfer Reactions 1 In order for the energy of ATP to be utilized for synthetic or other purposes, it must be transferred to the compounds which are directly involved in the process under consideration. A large number of primary and secondary group transfer reactions that carry out such energy trans-fers are known. If the product is itself an energy-rich compound, the reaction is reversible, but, if the product is of much lower energy than ATP or if water is introduced in the course of the reaction, the energy-rich character of the reacting group is lost and the process is essentially irreversible. The study of the nature and mechanism of these reactions constitutes a large part of contemporary biochemical investigation and several such reactions raise mechanistic questions that are of interest to organic and physical chemists as well as to biochemists. They are sur-veyed here according to reaction type, with no pretense of completeness. A. PHOSPHATE TRANSFER The terminal phosphate of ATP may be transferred to other nucleoside diphosphates, to give the corresponding triphosphates, or to nucleoside monophosphates to form the corresponding diphosphates [Eq. (7)]. Ο Ο ? 0 A d — Ο — Ρ — Ο — Ρ — Ο ί Ρ — O 4 + X D P ( X M P ) ^± A D P + X T P ( X D P ) (7) Ο Ο 5 0 As in the case of all other reactions of the terminal phosphate of ATP which have been examined with 0 1 8 -labeled substrates, the reaction occurs with terminal Ρ — 0 bond splitting, as shown, so that the reaction is a phosphoryl transfer. The nucleoside triphosphates so formed are them-selves phosphate or nucleotide donors for a number of further transfer reactions. Phosphate is also transferred from ATP to polymetaphosphate and, in a reversible reaction, to the serine hydroxyl group of phosphopro-teins. These polyphosphate compounds may serve as phosphate reservoirs.

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