Energy, Reactions & Enzymes PDF
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This document explains concepts related to energy, reactions, and enzymes, including energy types, reaction classifications (endergonic/exergonic), and enzyme function. It provides details about activation energy and enzyme regulation.
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ENERGY, REACTIONS & ENZYMES Student Learning Objectives: Energy & Reactions in Cells Define and differentiate between potential energy and Gibb’s free energy Define and contrast anabolic & catabolic reactions, giving an example of each Correlate the following terms & describe how the relate...
ENERGY, REACTIONS & ENZYMES Student Learning Objectives: Energy & Reactions in Cells Define and differentiate between potential energy and Gibb’s free energy Define and contrast anabolic & catabolic reactions, giving an example of each Correlate the following terms & describe how the relate to each other: endergonic/exergonic; anabolic/catabolic; condensation/hydrolysis Identify the activation energy, change in free energy (DG), and transition state on a graph of free energy change of a reaction Identify whether a reaction is endergonic or exergonic using a graph of the free energy change of a reaction ENERGY Capacity to do work or promote change Potential energy: energy due to position Chemical potential energy: energy in molecular bonds Energy can be converted into different forms but is conserved (total amount remains constant) GIBB’S FREE ENERGY (G) The energy within a molecule available for work Within a molecule, there are multiple sources of energy but only a portion is available for work. Examples of energy: vibrations, rotations, and energy stored within bonds between atoms (chemical potential energy) Free energy changes over the course of a reaction (DG) ENDERGONIC EXERGONIC - Free energy increases over the - Free energy decreases over the course of the reaction (+DG) course of the reaction (-DG) - Requires a continuous input of - Energy is released over the course of energy over the course of the the reaction reaction - Energetically favorable - Energetically unfavorable - Includes catabolic reactions (breaking - Include anabolic reactions (building) down) Label these reactions as endergonic or exergonic: BIOLOGICAL REACTION: Is this reaction exergonic or endergonic? Describe what is occurring to free energy over the course of the reaction. ACTIVATION ENERGY: Energy input required for reactants to reach a high energy transition state Ea o Relatively high due to stability of biological molecules o Energy often absorbed as heat from surroundings DG Is the activation included in the overall free energy change of a reaction (DG)? Reaction Rates & Activation Energy: Is this reaction anabolic or catabolic? Endergonic or Exergonic? Glucose Important reaction but must be sped up to be useful to cells. How? Addition of a protein catalyst = Enzyme Student Learning Objectives: Enzymes Draw how a graph of the free energy change of a reaction is altered in the presence of an enzyme and describe the effect on the rate of the reaction and the overall change in free energy of the reaction (DG) Identify the location of an active site on an enzyme and explain the role of the active site Contrast allosteric inhibition versus competitive inhibition Describe the process of negative feedback inhibition Predict how alterations in enzyme shape could affect enzyme function Predict the potential consequence of a nonfunctional enzyme for a cell and discuss the role of enzyme regulation in determining what reactions occur within a cell Describe the role of cofactors and coenzymes in enzyme function and contrast their structures REACTIONS WITH ENZYMES: What is altered with an enzyme? Activation energy How would this speed up the reaction? ENZYMES: Have a binding site = Active site Enzymes are highly specific to its reactants (substrates) Upon binding, an enzyme-substrate complex is formed Enzymes are not altered during reactions & can be re-used Nearly ALL biological reactions are catalyzed by enzymes! ENZYME REGULATION: How cells regulate what reactions are occurring Allosteric Regulation: Involves the binding of a small molecule to a site other than the active site to activate (activator) or inhibit (inhibitor) the enzyme. Is the small molecule CTP an allosteric activator or inhibitor? Competitive Inhibition: Inhibitor binds to the active site of the enzyme, preventing binding of substrate BIOSYNTHETIC PATHWAYS: Most cellular reactions are multi-step with each step catalyzed by a unique enzyme: REGULATION OF BIOSYNTHETIC PATHWAYS: 1 2 3 4 5 Product acts as an allosteric inhibitor of an early enzyme in the pathway ROLE OF COFACTORS & COENZYMES: Required by some enzymes to work or work efficiently: Cofactors – inorganic ions (ex. Mg2+, Zn2+) that may bind anywhere on enzyme Coenzymes – organic molecules that bind to active site & improve substrate binding Example: Vitamin C binding to enzyme