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Chapter 8: Metabolism & Enzymes Flow of energy through life Life is built on ___________________________ transforming __________ from one form to another Examples dehydration synthesis (synthesis) + enzyme Metabolism Chemical reactions of life HO o forming between molecules hydrolysis (digestion) _____________________ synthesis synthesis + enzyme reactions o Breaking between molecules HO AP Biology _________________________ digestion reactions Chemical reactions & energy o Some chemical reactions release energy Examples ________________________ dehydration synthesis (synthesis) digesting ____________________ hydrolysis = _________________ enzyme o Some chemical reactions require input of_____________________ _________________________ hydrolysis (digestion) ___________________ polymers dehydration synthesis = enzyme ________________ Energy & life AP Biology o Organisms require energy to live where does that energy come from? coupling reactions (___________________ energy) with ____________________ reactions (___________________ energy) What drives reactions? o If reactions are “__________________”, why don’t they just happen spontaneously? Endergonic vs. exergonic reactions because covalent bonds are exergonic endergonic ____________________ bonds - energy released - energy invested Activation energy - digestion - synthesis o Breaking down large molecules requires an initial ___________________ of energy _________________________ + G large biomolecules are _________ must absorb energy to break - G bonds Too much activation energy for _____________ o Activation energy AP Biology G = change in free energy = ability to do work amount of energy needed to _____________________________ the bonds of a molecule moves the reaction over an “___________________________” 2 2 Reducing Activation energy o _____________________ reducing the amount of energy to start a reaction _______________________ o So what’s a cell got to do to __________ activation energy? get help!…chemical help…Enzymes __________________ o Biological catalysts proteins (& RNA) facilitate chemical reactions increase rate of reaction without being __________________ reduce activation energy don’t change free energy (____) released or required required for most biological reactions highly___________________ _________________ of different enzymes in cells control reactions of __________ o Enzymes vocabulary _________________________ reactant which binds to enzyme enzyme-substrate complex: temporary association _________________________ end result of reaction _________________________ enzyme’s catalytic site; substrate fits into active site o Properties of enzymes Reaction specific each enzyme works with a specific __________________ chemical fit between ___________ site & substrate H bonds & ionic bonds Not in reaction single enzyme molecule can ________________ thousands or more reactions per second enzymes _________________ by the reaction Affected by conditions any condition that affects protein structure ________________________ o o o Naming conventions Enzymes named for reaction they catalyze _________________________ breaks down sucrose break down proteins break down lipids DNA builds DNA and adds nucleotides to DNA strand breaks down proteins (polypeptides) ____________________________________ model Simplistic model of _____________________ action substrate fits into 3-D structure of enzyme’ active site o ____________ bonds between substrate & enzyme like “key fits into lock” _____________________________________ model More accurate model of _____________________ action 3-D structure of enzyme fits substrate substrate binding cause enzyme to change leading to a tighter fit o “ change” o bring chemical groups in position to catalyze reaction How does it work? Variety of mechanisms to lower activation energy & speed up reaction o Synthesis - active site orients in correct position for reaction enzyme brings substrate _____________________ together o ___________________________ - active site binds substrate & puts stress on bonds that must be , making it easier to separate molecules Factors that Affect Enzymes Factors Affecting Enzyme Function o ____________________________ concentration o Substrate ______________________ o Temperature o ____________ o Salinity o _______________________ o Inhibitors Enzyme concentration o Factors affecting enzyme function Enzyme concentration as ________ enzyme = ________ reaction rate o more enzymes = more frequently ________________ with substrate ___________________________ rate levels off o substrate becomes _______________________________ o not all enzyme ___________________________ can find substrate Substrate concentration o Factors affecting enzyme function Substrate concentration as ______ substrate = ______ reaction rate o more substrate = more frequently ________________ with enzyme reaction rate levels off o all enzymes have active site _____________________ o enzyme is ________________________ o maximum _____________________ of reaction reaction rate reaction rate Temperature o Factors affecting enzyme function Optimum T° Enzymes and temperature greatest number of Different enzymes function in different molecular ________ organisms in different environments human enzymes = hot spring ____°- ____°C human enzyme bacteria enzyme o body temp = _____°C Heat: beyond optimum T° increased ________ level of molecules disrupts bonds in 37°C 70°C temperature AP Biology enzyme & between (158°F) enzyme & substrate o H, ionic = ____ bonds pH _________ = lose 3D What’s shape (3° structure) happening here?! Cold: T° molecules move _____ pepsin trypsin decrease collisions between __________ & substrate pepsin o Enzymes and __________________ Different enzymes function in trypsin different organisms in different environments 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH pH AP Biology o Factors affecting enzyme function changes in pH adds or removes _________ ____________________ bonds, disrupts _______ shape o disrupts attractions between charged ________________________ o affect ___° & ___° structure o ____________________ protein optimal pH? most human enzymes = pH 6-8 o depends on localized conditions o pepsin (stomach) = pH 2-3 o trypsin (small intestines) = pH 8 Salinity o Factors affecting enzyme function Salt concentration changes in ____________________ o adds or removes _____________ (+) & _____________ (–) o disrupts _______________, disrupts 3D shape disrupts attractions between _______________ amino acids affect ___° & ___° structure _________________________ protein enzymes _______________________ of extreme salinity o _________________________ is called dead for a reason! Compounds which help enzymes o Activators __________________________ non-protein, small ________________________ compounds & ions o Mg, K, Ca, Zn, Fe, Cu o bound __________________ enzyme molecule __________________________ non-protein, _________________ molecules o bind temporarily or permanently to enzyme near ________________ many _____________________ o NAD (___________________; B3) o FAD (____________________; B2) o _______________________ A Compounds which regulate enzymes o ___________________________ molecules that reduce enzyme activity _______________________ inhibition _______________________ inhibition _______________________ inhibition _______________________ inhibition o ____________________________ Inhibitor Inhibitor & substrate “_________________________” for active site ______________________ blocks enzyme bacteria use to build cell walls disulfiram (________________________) treats chronic alcoholism o blocks enzyme that breaks down ______________________ o severe hangover & _______________ 5-10 minutes after drinking Overcome by _________________________ substrate concentration saturate solution with substrate so it ______________________________ inhibitor for active site on enzyme o Non-Competitive Inhibitor Inhibitor binds to site other than active site _________inhibitor binds to allosteric site causes enzyme to change ______________ o conformational change o active site is no longer functional __________________ site keeps enzyme __________ some drugs inhibit enzymes involved in DNA synthesis o stop _________ production o stop division of more cancer _____ irreversible inhibitor of Cytochrome C, an enzyme in cellular respiration o stops production of __________ o Irreversible inhibition Inhibitor ______________________ binds to enzyme competitor o permanently binds to _______________________ _______________________ o permanently binds to allosteric site o permanently changes __________________ of enzyme o nerve gas, sarin, many insecticides (malathion, parathion…) ___________________________ inhibitors doesn’t breakdown the neurotransmitter, __________ o Allosteric regulation Conformational changes by ________________ molecules _____________- keeps enzyme in inactive form ____________ - keeps enzyme in active form ______________________ pathways o Chemical reactions of life are organized in ___________________ divide chemical reaction into many _____________ steps artifact of _________________________ ___ efficiency o intermediate branching points threonine ___ control = ___________________ Efficiency Example o _______________________ groups of enzymes enzymes are embedded in membrane of andamino arranged synthesis _______________________ acid, isoleucine from o Link ________________________ & exergonic reactions amino acid, threonine Feedback Inhibition isoleucine becomes o _______________________ & coordination of production the allosteric in pathway product is used by next _____________ inhibitor of the firststep ______________ product is inhibitor of earlier stepofin the____________ pathway allosteric inhibitor earlier _____________________ inhibition as product no unnecessary ____________________ accumulates itof product collides with enzyme o Example more often than synthesis of amino acid, ______________________ substrate does isoleucin from amino acid, __________________________ AP Biology e isoleucine becomes the inhibitor of the first step in the pathway as product _________________________ it collides with enzyme more often than substrate does Feedback inhibition