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Transcript
AP Biology From food webs to the life of a cell energy Metabolism & Enzymes energy gy energy AP Biology AP Biology Flow of energy through life Life is built on chemical reactions transforming energy from one form to organic molecules → ATP another & organic molecules Metabolism Chemical reactions of life ___________________ between molecules dehydration synthesis synthesis sun organic molecules → ATP & organic molecules _______________________ ___________________ between molecules hydrolysis digestion _______________________ solar energy → AP Biology ATP & organic molecules AP Biology That’s why they’re called anabolic steroids! 1 AP Biology Examples dehydration synthesis (synthesis) Examples dehydration synthesis (synthesis) + enzyme enzyme H2O hydrolysis (digestion) enzyme hydrolysis (digestion) + enzyme H2O AP Biology AP Biology Chemical reactions & energy Some chemical reactions release energy ___________________ digesting polymers hydrolysis = catabolism digesting molecules= LESS organization= lower energy state Endergonic vs. exergonic reactions exergonic endergonic - energy released - digestion - energy invested - synthesis Some chemical reactions require input of energy +ΔG building molecules= ___________________ MORE organization= higher energy state building polymers dehydration synthesis = anabolism AP Biology -ΔG AP Biology ΔG = change in free energy = ability to do work 2 AP Biology Energy & life Organisms require energy to live What drives reactions? If reactions are “downhill”, why don’t they where does that energy come from? coupling exergonic reactions (releasing energy) just happen spontaneously? because covalent bonds are stable bonds with endergonic reactions (needing energy) Why don’t stable polymers spontaneously digest into their monomers? starch + + energy synthesis synthesis + + energy AP Biology AP Biology Activation energy Breaking down large molecules requires an initial input of energy ___________________________ large biomolecules are stable must absorb energy to break bonds AP Biology cellulose energy CO2 + H2O + heat Too much activation energy for life Activation energy amount of energy needed to destabilize the bonds of a molecule moves the reaction over an “energy hill” glucose Not a match! That’s too much energy to expose living cells to! AP Biology 3 AP Biology Reducing Activation energy ___________________ reducing the amount of energy to start a reaction uncatalyzed reaction Catalysts So what’s a cell got to do to reduce activation energy? get help! … chemical help… ____________ Pheeew… that takes a lot less energy! Call in the ENZYMES! uncatalyzed reaction NEW activation energy ΔG reactant product AP Biology AP Biology Enzymes Biological catalysts _________________________ _________________________ increase rate of reaction without being consumed reduce activation energy don don’tt change free energy (ΔG) released or required Enzymes vocabulary _________________________ reactant which binds to enzyme enzyme-substrate complex: temporary association _________________________ end result of reaction _________________________ required for most biological reactions _________________________ enzyme’s catalytic site; substrate fits into active site thousands of different enzymes in cells AP Biology control reactions of life active site substrate products enzyme AP Biology 4 AP Biology Properties of enzymes _________________________ Naming conventions Enzymes named for reaction they catalyze each enzyme works with a specific substrate chemical fit between active site & substrate H bonds & ionic bonds _________________________ single enzyme molecule can catalyze thousands or more reactions per second ____________ breaks down sucrose ____________ break down proteins ____________ break down lipids ____________ builds DNA adds nucleotides to DNA strand enzymes unaffected by the reaction _________________________ any condition that affects protein structure ____________ breaks down proteins (polypeptides) temperature, pH, salinity AP Biology AP Biology Lock and Key model Simplistic model of enzyme action substrate fits into 3-D structure of enzyme’ active site H bonds between substrate & enzyme AP Biology In biology… Size doesn’t matter… Shape matters! Induced fit model More accurate model of enzyme action 3-D structure of enzyme fits substrate substrate binding cause enzyme to change shape leading to a tighter fit “conformational change” bring chemical groups in position to catalyze reaction like “key fits into lock” AP Biology 5 AP Biology How does it work? Variety of mechanisms to lower activation energy & speed up reaction Got any Questions?! synthesis active site orients substrates in correct position for reaction enzyme brings substrate closer together digestion active site binds substrate & puts stress on bonds that must be broken, making it easier to separate molecules AP Biology AP Biology 2007-2008 Factors Affecting Enzyme Function ________________________ ________________________ ________________________ ________________________ ________________________ ________________________ ________________________ Factors that Affect Enzymes AP Biology 2007-2008 AP Biology catalase 6 AP Biology Enzyme concentration Factors affecting enzyme function Enzyme concentration What’s happening here?! as ↑ enzyme = ↑ reaction rate more enzymes = more frequently collide with substrate reaction rate reaction rate levels off reaction rate substrate becomes limiting factor not all enzyme molecules can find substrate enzyme concentration AP Biology AP Biology enzyme concentration Substrate concentration Factors affecting enzyme function Substrate concentration What’s happening here?! as ↑ substrate = ↑ reaction rate more substrate = more frequently collide with enzyme reaction rate reaction rate all enzymes have active site engaged enzyme is saturated maximum rate of reaction substrate concentration AP Biology reaction rate levels off AP Biology substrate concentration 7 AP Biology Temperature Factors affecting enzyme function Temperature What’s happening here?! ________________________________ greatest number of molecular collisions human enzymes = 35°- 40°C ________________________________ increased energy level of molecules disrupts bonds in enzyme & between enzyme & substrate reaction rate e body temp = 37°C 37° temperature AP Biology H, ionic = weak bonds ________________ = lose 3D shape (3° structure) ________________________________ molecules move slower decrease collisions between enzyme & substrate AP Biology Enzymes and temperature Different enzymes function in different How do ectotherms do it? organisms in different environments hot spring bacteria enzyme reaction rate human enzyme 37°C AP Biology temperature 70°C (158°F) AP Biology 8 AP Biology pH Factors affecting enzyme function pH What’s happening here?! pepsin 0 1 2 3 4 5 6 7 8 9 10 11 12 optimal pH? most human enzymes = pH 6-8 depends on localized conditions pepsin (stomach) = pH 2-3 trypsin (small intestines) = pH 8 trypsin AP Biology changes in pH adds or remove H+ ________________________________________ disrupts p attractions between charged g amino acids affect 2° & 3° structure denatures protein trypsin reaction rate pepsin 13 14 pH AP Biology Salinity What’s happening here?! 0 1 2 3 4 5 6 7 8 9 10 11 Factors affecting enzyme function Salt concentration changes in salinity adds or removes cations (+) & anions (–) reaction rate e ________________________________________ disrupts attractions between charged amino acids affect 2° & 3° structure denatures protein enzymes intolerant of extreme salinity Dead Sea is called dead for a reason! salt concentration AP Biology AP Biology 9 AP Biology Compounds which help enzymes Fe in Activators hemoglobin Compounds which regulate enzymes Inhibitors _______________________ molecules that reduce enzyme activity ____________________________ ____________________________ non-protein, small inorganic compounds & ions Mg, K, Ca, Zn, Fe, Cu bound within enzyme molecule _______________________ non-protein, organic molecules bind temporarily or permanently to ____________________________ ____________________________ enzyme near active site AP Biology many vitamins NAD (niacin; B3) FAD (riboflavin; B2) Coenzyme A Mg in chlorophyll Competitive Inhibitor Inhibitor & substrate “compete” for active site penicillin blocks enzyme bacteria use to build cell walls disulfiram (Antabuse) treats chronic alcoholism blocks enzyme that breaks down alcohol severe hangover & vomiting 5-10 minutes after drinking AP Biology Non-Competitive Inhibitor Inhibitor binds to site other than active site conformational change Overcome by increasing substrate AP Biology saturate solution with substrate so it out-competes inhibitor for active site on enzyme active site is no longer functional binding site keeps enzyme inactive some anti-cancer drugs inhibit enzymes involved in DNA synthesis stop DNA production stop division of more cancer cells concentration _______________________________________ causes enzyme to change shape cyanide poisoning irreversible inhibitor of Cytochrome C, an enzyme in cellular respiration stops production of ATP AP Biology 10 AP Biology Irreversible inhibition Inhibitor permanently binds to enzyme ____________________________ permanently binds to active site ____________________________ permanently binds to allosteric site Allosteric regulation Conformational changes by regulatory molecules inhibitors activators keeps enzyme in inactive form keeps enzyme in active form permanently changes shape of enzyme nerve gas, sarin, many insecticides (malathion, parathion…) cholinesterase inhibitors doesn’t breakdown the neurotransmitter, acetylcholine AP Biology Conformational AP Biology Metabolic pathways → → → → → → → A→B→C→D→E→F→G 2 3 4 5 6 Chemical reactions of life are organized in pathways AP Biology divide chemical reaction into many small steps artifact of evolution ↑ efficiency intermediate branching points ↑ control = regulation Allosteric regulation Efficiency Organized groups of enzymes enzyme enzyme enzyme enzyme enzyme enzyme enzyme 1 changes enzymes are embedded in membrane and arranged sequentially Link endergonic & exergonic reactions Whoa! All that going on in those little mitochondria! AP Biology 11 AP Biology threonine Feedback Inhibition Feedback inhibition Regulation & coordination of production product is used by next step in pathway final product is inhibitor of earlier step ____________________________ no unnecessary accumulation of product → → → → → → A→B→C→D→E→F→G 1 2 3 4 5 6 X enzyme enzyme enzyme enzyme enzyme enzyme AP Biology synthesis of amino acid, isoleucine from amino acid, threonine isoleucine becomes the allosteric inhibitor of the first step in the pathway allosteric inhibitor of earlier enzyme Example allosteric inhibitor of enzyme 1 as product accumulates it collides with enzyme more often than substrate does AP Biology isoleucin e Don’t be inhibited! Ask Questions! AP Biology 2007-2008 12
