Energy, Reactions & Enzymes PDF

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