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This 4 page Class Notes was uploaded by Emily Liescheidt on Wednesday October 14, 2015. The Class Notes belongs to bio120 at Grand Valley State University taught by Simon in Fall 2015. Since its upload, it has received 16 views. For similar materials see General Biology in Biology at Grand Valley State University.
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Date Created: 10/14/15
Energy and Metabolism 1 Energy the ability to do work 1 Three types of energy 1 Kinetic Energy this is energy that is in use 1 present in object that are moving 2 release of energy due to a chemical reaction 2 Thermal Energyheat random movement of atoms and molecules 1 includes solar or light energy 3 Potential Energy stored energy that can be used Laws of Thermodynamics 1 Energy can be transferred or transformed but it cannot be destroyed 2 Every energy transfer or transformation increases the spontaneous vs non spontaneous 1 Spontaneous reactions release energy 1 more freepotential energy in reactants than products 1 This results in a negative change in G 2 Maltose Glucose Glucose 2 Non spontaneous reactions Energy input 1 There is less potential energy in the reactants than there is in the products 2 There is a change in G 1 Positive because energy is added 2 Glucose Glucose Maltose 3 Spontaneous exergonic release of energy 4 nonspontaneous endergonic input reaction Reactions 1 That occur in closed systems 1 reach equilibrium 1 as a result there is no energy to do work 2 if this occurs in a cell the cell would die 2 Cells are an open system no equilibrium is reached because there is a constant flow of material into and out of the cell 1 the cell continues to do work energy is always supplied 3 Our reactions take place in metabolic pathways 1 In a metabolic pathway products of one reaction are reactants of the next reaction 2 metabolic pathway is a series of related reactions 1 both endergonic and exergonic reactions occur in metabolic pathways 2 Why do our cells use stepwise pathway 1 It controls the production of products and the intake and release of energy 2 it also helps prevent equilibrium because products are used as reactants Cells do three kinds of work 1 Chemical work synthesizing polymers from monomers 1 bonding amino acids together to form peptide bonds 2 Transport work active transport that requires energy Mechanical work muscle contractions the movement of flagella or cilia 4 All forms of work require energy 1 they are endergonic energy is added therefore change in G is positive 5 ATP Energy source to do work 1 ATP has three components 1 Three phosphate groups 1 phosphate group is the same thing as inorganic phosphate 1 usually represent that by using Psub i 2 Ribose sugar 3 Nitrogenous base adenine 2 How does ATP actually fuel reactions 1 Hydrolysis of ATP releases a phosphate group breaking of bond releasing energy 2 We are taking ATP hydrolyzing it creating ADP plus Pi plus energy remove one energy group and it becomes diphosphate 4 Energy works by mediating energy coupling 1 energy required for an endergonic reaction is less than the energy release by ATP hydrolysis the combination of the two reactions are overall exergonic 1 meaning there is energy left over 2 Examples of using ATP to do work 3 ATP cycle 1 ATP and water results in hydrolysis of ATP produces ADP the inorganic phosphate energy 2 released energy does work it is an endergonic process because it used energy 3 ADP inorganic PhosphateBecause ATP was hydrolyzed now we need to make ATP 1 We need energy because we are building a bond between ADP and the inorganic phosphate This comes from the metabolism of an organic moleculemaybe the sugar supply from the candy bar eaten at lunch 4 ADP lnorganic phosphate energy produces ATP which can be used as an energy source by the cell 5 Then the process starts over 6 Spontaneous reactions they are exergonic they release energy 1 They have a negative Delta G indicates the release of energy 2 spontaneous reactions are catabolic meaning bonds are broken 7 Nonspontaneous reactins they are endergonic because energy is input 1 there is a positive delta G 2 they are anabolic meaning bonds are built 6 Metabolism enzymes are also used to do work 9 9 1 Enzymes are protein moleculesal enzymes are made of proteins that facilitate reactions 1 They make it easier for reactions to occur 1 This means the reaction rate increasesthey occur more quickly 2 Enzymes are catalysts 1 They catalyze endergonic and exergonic reactions 2 Metabolism the total of all chemical reactions performed by an organism 2 Reaction without enzymes 1 reactants must reach a transition state 1 Transition state is the point at which the bonds of the reactants are unstable 1 as a result it is easier to convert reactants to products 2 Reactions use activation energy which is energy absorbed from the environment Thermal energy to reach that transition state 3 Activation Energy is Esub A 7 The effects of enzymes on reaction rate 1 Enzymes will work at body temperature 1 They lower the amount of activation energy requiredEsub A 1 The reaction occurs fasterit reaches transition state sooner 2 Activation energy the amount of energy needed to destabilize the bonds of the reactants and start the reactionhas nothing to do with delta G 3 Delta G this is the amount of energy input or release due to conversion of the reactants to the products 4 Enzymes are substrate specific that means that they work with a specific organic molecules 1 Why can an enzyme be so specific 1 Enzymes are composed of protein and each protein has a specific 3D shape which is determined by primary structureamino acid sequence 5 Active site this is the site at which the substrates bond 1 the active site is on the enzyme 2 substrate enters the active site and the enzyme changes shape 3 enzymes and substrates are specific to each other they fit to each other like a lock and keyinduced fit 1 Enzyme is the lock 2 Substrate is the key 6 Enzymes have an optimal temperature at which they will function 1 Thermophilic bacteria operates at a much higher temperature than the enzymes in the human body 2 An increase in body temperature increases enzyme activity due to the increase in molecular movement 3 When the temperature increases too much there is a decrease in enzyme activity due to the denatured enzymethey lose their structure 4 Enzymes also have an optimal pH for function it varies from location to location 7 Environmental factors affect the function of an enzyme 1 Enzyme function can also be decreased due to chemical alteration of the enzyme 1 Cofactornon protein portion of an enzyme usually metal ion like zinc iron copper 2 There are also coenzymes that may or may not be attached to the enzyme itself but it is essential and usually organic molecules 1 vitamins are used to make these organic molecules 1 for instance vitamin B3 to coenzyme A 1 Coenzyme A is used in cellular respiration Enzyme inhibition 1 This is caused by the bonding of another molecule to the enzyme 1 if the bonds are weak then the inhibition is reversible 2 if the bonds are strongcovalent then it is not reversible Enzyme regulation enzymes are activated and deactivated based on the needs of the cell 1 This results in feedback inhibition Enzyme inhibitors 1 Competitive inhibitor bonds to the active site of the enzyme so it competes with the substrate for the active site 1 This is reversible if the substrate concentration is increased 2 it increases the probability that substrate will bond to the active site when it s available 2 Noncompetitive inhibition bonds to a site on an enzyme that is not the active site 1 It changes the shape of the enzyme thus changing the shape of the active site 2 This means the substrate cannot bond 3 These are toxinspoisons which means this is nonreversible 4 Cells use naturally occurring compounds which are reversible and are used to regulate enzyme activity
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