AP Biology 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 Factors that Affect Enzymes

AP Biology Factors Affecting Enzyme Function  Enzyme concentration  Substrate concentration  Temperature  pH  Salinity  Activators  Inhibitors catalase

AP Biology Enzyme concentration enzyme concentration reaction rate What’s happening here?!

AP Biology Factors affecting enzyme function  Enzyme concentration  as  enzyme =  reaction rate  more enzymes = more frequently collide with substrate  reaction rate levels off  substrate becomes limiting factor  not all enzyme molecules can find substrate enzyme concentration reaction rate

AP Biology Substrate concentration substrate concentration reaction rate What’s happening here?!

AP Biology Factors affecting enzyme function substrate concentration reaction rate  Substrate concentration  as  substrate =  reaction rate  more substrate = more frequently collide with enzyme  reaction rate levels off  all enzymes have active site engaged  enzyme is saturated  maximum rate of reaction

AP Biology 37° Temperature temperature reaction rate What’s happening here?!

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 37°C temperature reaction rate 70°C human enzyme hot spring bacteria enzyme (158°F)

AP Biology How do ectotherms do it?

AP Biology 7 pH reaction rate pepsintrypsin What’s happening here?! pepsin trypsin

AP Biology 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

AP Biology Salinity salt concentration reaction rate What’s happening here?!

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  Activators  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  many vitamins  NAD (niacin; B3)  FAD (riboflavin; B2)  Coenzyme A Mg in chlorophyll Fe in hemoglobin

AP Biology 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  saturate solution with substrate so it out-competes inhibitor for active site on enzyme

AP Biology 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 doesn’t breakdown the neurotransmitter, acetylcholine

AP Biology Allosteric regulation  Conformational changes by regulatory molecules  inhibitors  keeps enzyme in inactive form  activators  keeps enzyme in active form Conformational changesAllosteric regulation

AP Biology Metabolic pathways A  B  C  D  E  F  GA  B  C  D  E  F  G enzyme 1  enzyme 2  enzyme 3  enzyme 4  enzyme 5  enzyme 6   Chemical reactions of life are organized in pathways  divide chemical reaction into many small steps  artifact of evolution   efficiency  intermediate branching points   control = regulation A  B  C  D  E  F  GA  B  C  D  E  F  G enzyme 

AP Biology 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 allosteric inhibitor of enzyme 1 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 A  B  C  D  E  F  GA  B  C  D  E  F  G enzyme 1  enzyme 2  enzyme 3  enzyme 4  enzyme 5  enzyme 6  X

AP Biology 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 threonine isoleucin e

AP Biology Don’t be inhibited! Ask Questions!

AP Biology Ghosts of Lectures Past (storage)

AP Biology Cooperativity  Substrate acts as an activator  substrate causes conformational change in enzyme  induced fit  favors binding of substrate at 2 nd site  makes enzyme more active & effective  hemoglobin Hemoglobin  4 polypeptide chains  can bind 4 O 2 ;  1 st O 2 binds  now easier for other 3 O 2 to bind

AP Biology Lorenzo’s Oil