Rebecca Davenport BIOL 1406 BW1 10 10 16 Ch 8 blue print Energy and Metabolism 1 Metabolism the totality of an organism chemical reactions a A metabolic pathway begins with a specific molecule and ends with a product i Multistep process series of reactions to get desired product b Each step is catalyzed by a specific name c d Metabolism Catabolism Anabolism i Anabolic pathways consume energy to build complex molecules from simpler ones 1 Requires energy 2 Ex Synthesis of proteins from amino acids ii Catabolic pathways release energy by breaking down complex molecules into simpler compounds 1 Bonds break and form which releases energy and forms lower energy breakdown products 2 Ex Breaking down starch into glucose molecules 2 Energy ability to promote change or do work a 2 forms i Kinetic associated with movement 1 Thermal energy is kinetic energy associated with random movement of atoms or molecules a Does not contribute to work not useful ii Potential due to structure or location 1 Chemical energy is energy stored in molecular bonds b 2 laws of Thermodynamics i First law1 Law of conservation of energy 2 Energy cannot be created or destroyed BUT 3 Can be transformed from one type to another ii Second law1 Transfer or transformation of energy from one form to another increases entropy 2 Entropy is a measure of disorder S 3 During every energy transfer or transformation some energy is unusable and is often lost as heat c Free energy the energy available to do work useful 1 denoted by the symbol G Gibb s free energy ii Measure of a system s instability 1 Unstable system has a higher G and higher energy 2 More stable system has a lower G and lower energy 3 Systems want to move towards greater stability iii Key factor is the free energy change 1 G Gfinal Ginitial 2 3 A negative number tells us we lost energy aka more stable Postive number means we gained energy aka less stable iv Spontaneous and Nonspontaneous Reactions 1 Spontaneous or Exergonic Energetically favorable aka wants to happen a G 0 or negative free energy change G b No input of energy c Not necessarily fast d Release energy 2 Not spontaneous or Endergonic energetically unfavorable a G 0 or positive free energy change G b Requires addition of free energy c Needs energy Transition state Activation energy 3 d ATP Adenosine triphosphate Adenine ribose 3 phosphate the 3 phos All have negative charges which don t like to be so close so when you cut one off it springs away releasing energy aka ATP hydrolysis i Energy is released ii Energy that can drive a variety of cellular processes iii G 7 3 kcal mole iv ATP Hydrolysis1 Energy coupling An endergonic reaction can be coupled to an exergonic reaction endergonic reaction drives exergonic reaction 2 Both reactions as a couple will be spontaneous if net free energy change for both processes together negative 3 ATP drives endergonic reactions by phosphorylation a transferring a phosphate group to some other molecule b The recipient molecule is called a phosphorylated intermediate 4 e Activation Energy Initial input of energy required to start reaction i For a reaction to occur need to contort reactant into an unstable form 1 Requires energy from surroundings normally heat ii Transition State unstable condition where bonds are able to break iii This can be a very slow process 3 Enzymes proteins that act as a catalyst a What s the purpose of an enzyme To speed up a reaction b Decrease activation energy for reactions c Conformation affected by environmental conditions i Temp pH can affect folding activity 1 If it s not folded it s not functional d e Enzyme features i Active site location where reaction takes place ii Substrate reactants that bind to active site for the reaction to occur iii Enzyme substrate complex formed when enzyme and substrate bind 1 Induced fit binding initiates the enzyme to change shape slightly so the substrate does not fall out before reaction is complete f iv Factors effecting enzymes i Environmental conditions temperature pH chemicals ii Inhibitors decrease enzymatic activity 1 May be competitive or noncompetitive a Ex toxins poisons pesticides and antibiotics 2 Competitive Inhibitiona Molecule binds to active site b Inhibits ability of substrate to bind c 3 Noncompetitive inhibition binds to allosteric site and warps the active site so the substrate cannot pair with enzyme a Allosteric Inhibition inhibitor binds to allosteric site not active site i Allosteric regulation of enzymes may either inhibit or stimulate an enzyme activity 1 Occurs when a regulatory molecule binds to a protein at one site and affects the protein s function at another site 2 Many enzymes have active and inactive forms a The binding of an activator stabilizes the active form of the enzyme b The binding of an inhibitor stabilizes the inactive form of the enzyme 3 4 Feedback inhibition the end product of a metabolic pathway shuts down the pathway a Prevents a cell from wasting chemical resources by synthesizing more product than is needed b iii Activators enhance ability of enzyme to catalyze a reaction
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