October 10 AP Biology - John D. O'Bryant School of Math & Science
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AP Biology John D. O’Bryant School of Mathematics and Science October 10, 2012 AP Biology Agenda Do Now (Quiz) Nobel Prize in Chemistry Lactose Intolerance video Experimental Design: Lactose Intolerance, etc. AP Biology Do Now (Quiz) 1. Which of the following statements is true concerning catabolic pathways? A) They combine molecules into more energy-rich molecules. B) They are usually coupled with anabolic pathways to which they supply energy in the form of ATP. C) They are endergonic. D) They are spontaneous and do not need enzyme catalysis. E) They build up complex molecules such as protein from simpler compounds. AP Biology Do Now (Quiz) 2. When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated? A) It is used to power yet more cellular work. B) It is used to store energy as more ATP. C) It is used to generate ADP from nucleotide precursors. D) It is lost to the environment. E) It is transported to specific organs such as the brain. AP Biology Do Now (Quiz) 3. During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a △G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the △G for the new reaction? A) -40 kcal/mol B) -20 kcal/mol C) 0 kcal/mol D) +20 kcal/mol E) +40 kcal/mol AP Biology Do Now (Quiz) 4. According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? A) The binding of the substrate depends on the shape of the active site. B) Some enzymes change their structure when activators bind to the enzyme. C) A competitive inhibitor can outcompete the substrate for the active site. D) The binding of the substrate changes the shape of the enzyme's active site. E) The active site creates a microenvironment ideal for the reaction. AP Biology Do Now (Quiz) 5. Which of the following is likely to lead to an increase in the concentration of ATP in a cell? A) an increase in a cell's anabolic activity B) an increase in a cell's catabolic activity C) an increased influx of cofactor molecules D) an increased amino acid concentration E) the cell's increased transport of materials to the environment AP Biology Do Now (Quiz) 6. The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as A) metabolic inhibition. B) feedback inhibition. C) allosteric inhibition. D) noncooperative inhibition. E) reversible inhibition. AP Biology Do Now (Quiz) 7. If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to A) add more of the enzyme. B) heat the solution to 90°C. C) add more substrate. D) add an allosteric inhibitor. E) add a noncompetitive inhibitor. AP Biology Metabolism & Enzymes AP Biology 2007-2008 Factors that Affect Enzymes AP Biology 2007-2008 Factors Affecting Enzyme Function Enzyme concentration Substrate concentration Temperature pH Salinity Activators Inhibitors AP Biology catalase Enzyme concentration reaction rate What’s happening here?! enzyme concentration AP Biology Factors affecting enzyme function Enzyme concentration as enzyme = reaction rate more enzymes = more frequently collide with substrate reaction rate levels off reaction rate substrate becomes limiting factor not all enzyme molecules can find substrate AP Biology enzyme concentration Substrate concentration reaction rate What’s happening here?! substrate concentration AP Biology Factors affecting enzyme function Substrate concentration as substrate = reaction rate more substrate = more frequently collide with enzyme reaction rate levels off reaction rate all enzymes have active site engaged enzyme is saturated maximum rate of reaction AP Biology substrate concentration Temperature reaction rate What’s happening here?! 37° temperature AP Biology Factors affecting enzyme function Temperature Optimum T° greatest number of molecular collisions human enzymes = 35°- 40°C body temp = 37°C Heat: increase beyond optimum T° increased energy level of molecules disrupts bonds in enzyme & between enzyme & substrate H, ionic = weak bonds denaturation = lose 3D shape (3° structure) Cold: decrease T° molecules move slower decrease collisions between enzyme & substrate AP Biology Enzymes and temperature Different enzymes function in different organisms in different environments reaction rate human enzyme hot spring bacteria enzyme 37°C AP Biology temperature 70°C (158°F) How do ectotherms do it? AP Biology pH What’s happening here?! trypsin reaction rate pepsin pepsin trypsin 0 AP Biology 1 2 3 4 5 6 pH 7 8 9 10 11 12 13 14 Factors affecting enzyme function pH changes in pH adds or remove H+ disrupts bonds, disrupts 3D shape disrupts attractions between charged amino acids affect 2° & 3° structure denatures protein optimal pH? most human enzymes = pH 6-8 depends on localized conditions pepsin (stomach) = pH 2-3 trypsin (small intestines) = pH 8 AP Biology 0 1 2 3 4 5 6 7 8 9 10 11 Salinity reaction rate What’s happening here?! salt concentration AP Biology Factors affecting enzyme function Salt concentration changes in salinity adds or removes cations (+) & anions (–) disrupts bonds, disrupts 3D shape 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! AP Biology Compounds which help enzymes Fe in Activators hemoglobin cofactors non-protein, small inorganic compounds & ions Mg, K, Ca, Zn, Fe, Cu bound within enzyme molecule coenzymes 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 Compounds which regulate enzymes Inhibitors molecules that reduce enzyme activity competitive inhibition noncompetitive inhibition irreversible inhibition feedback inhibition AP Biology 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 Overcome by increasing substrate concentration AP Biology saturate solution with substrate so it out-competes inhibitor for active site on enzyme Non-Competitive Inhibitor Inhibitor binds to site other than active site allosteric inhibitor binds to allosteric site causes enzyme to change shape conformational change 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 cyanide poisoning irreversible inhibitor of Cytochrome C, an enzyme in cellular respiration stops production of ATP AP Biology Irreversible inhibition Inhibitor permanently binds to enzyme competitor permanently binds to active site allosteric permanently binds to allosteric site permanently changes shape of enzyme nerve gas, sarin, many insecticides (malathion, parathion…) cholinesterase inhibitors AP Biology doesn’t breakdown the neurotransmitter, acetylcholine Allosteric regulation Conformational changes by regulatory molecules inhibitors keeps enzyme in inactive form activators keeps enzyme in active form AP Biology Conformational changes Allosteric regulation Metabolic pathways ABCDEFG 5 6 enzyme enzyme enzyme enzyme enzyme enzyme enzyme 1 2 3 4 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 Efficiency Organized groups of enzymes enzymes are embedded in membrane and arranged sequentially Link endergonic & exergonic reactions Whoa! All that going on in those little mitochondria! AP Biology Feedback Inhibition Regulation & coordination of production product is used by next step in pathway final product is inhibitor of earlier step allosteric inhibitor of earlier enzyme feedback inhibition no unnecessary accumulation of product ABCDEFG 1 2 3 4 5 6 X enzyme enzyme enzyme enzyme enzyme enzyme AP Biology allosteric inhibitor of enzyme 1 threonine Feedback inhibition Example synthesis of amino acid, isoleucine from amino acid, threonine isoleucine becomes the allosteric inhibitor of the first step in the pathway 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 Ghosts of Lectures Past (storage) AP Biology 2007-2008 Cooperativity Substrate acts as an activator substrate causes conformational change in enzyme induced fit favors binding of substrate at 2nd site makes enzyme more active & effective hemoglobin Hemoglobin 4 polypeptide chains can bind 4 O2; 1st O2 binds now easier for other O2 to bind AP3Biology Lorenzo’s Oil AP Biology
