Bioenergetics: The Role of ATP 2023 PDF

BIOENERGETICS: THE ROLE OF ATP Dr. Sebnem Garip Ustaoglu  Biologic Systems Conform to the General Laws of Thermodynamics ‘The total energy of a system, including its surroundings, remains constant’ ‘The total entropy of a system must increase if a process is to occur spontan...

BIOENERGETICS: THE ROLE OF ATP Dr. Sebnem Garip Ustaoglu  Biologic Systems Conform to the General Laws of Thermodynamics ‘The total energy of a system, including its surroundings, remains constant’ ‘The total entropy of a system must increase if a process is to occur spontaneously’  The Equilibrium Constant The equilibrium constant gives the relative concentration of reactants and products at equilibrium.  Exergonic and Endergonic Reactions ∆G° = free energy of the products - free energy of the reactants the relationship between ∆G° and Keq : ΔG° = −RT lnKeq ∆G° negative: exergonic reaction ∆G° positive: endergonic reaction Coupling of an exergonic to an endergonic reaction  Catabolic & Anabolic Rxns an endergonic process cannot exist independently, but must be a component of a coupled exergonic endergonic system where the overall net change is exergonic. The exergonic reactions are termed catabolism (generally, the breakdown or oxidation of fuel molecules), whereas the synthetic reactions that build up substances are termed anabolism. The combined catabolic and anabolic processes constitute metabolism. Coupling of dehydrogenation and hydrogenation reactions by an intermediate carrier  Transfer of free energy from an exergonic to an endergonic reaction via a high-energy intermediate compound An alternative method of coupling an exergonic to an endergonic process is to synthesize a compound of high- energy potential in the exergonic reaction and to incorporate this new compound into the endergonic reaction, thus effecting a transference of free energy from the exergonic to the endergonic pathway  Adenosine triphosphate (ATP) In the living cell, the principal high-energy intermediate or carrier compound is adenosine triphosphate (ATP). ATP is a nucleotide consisting of the nucleoside adenosine (adenine linked to ribose), and three phosphate groups. HIGH-ENERGY PHOSPHATES PLAY A CENTRAL ROLE IN ENERGY CAPTURE AND TRANSFER High energy Anhydrate bonds Low energy Ester bond ATP contains two high-energy phosphate groups and ADP contains one, whereas the phosphate in AMP (adenosine monophosphate) is of the low- energy type since it is a normal ester link. The high free-energy change on hydrolysis of ATP is due to relief of charge repulsion of adjacent negatively charged oxygen atoms and to stabilization of the reaction products, especially phosphate, as resonance hybrids Standard Free Energy of Hydrolysis of Some Organophosphates of Biochemical Importance  ATP/ADP cycle an ATP/ADP cycle connects those processes that generate to those processes that utilize , continuously consuming and regenerating ATP. Adenylate kinase is important for the maintenance of energy homeostasis in cells because it allows: 1. High-energy phosphate in ADP to be used in the synthesis of ATP. 2. The AMP formed as a consequence of activating reactions involving ATP to rephosphorylated to ADP. 3. AMP to increase in concentration when ATP becomes depleted so that it is able to act as a metabolic (allosteric) signal to increase the rate of catabolic reactions, which in turn lead to the generation of more ATP THANK YOU