AP Biology Metabolism & Enzymes

AP Biology From food webs to the life of a cell energy

AP Biology Flow of energy through life  Life is built on chemical reactions  Transforming energy from one form to another  Most reactions are spontaneous organic molecules  ATP & organic molecules sun solar energy  ATP & organic molecules

AP Biology Metabolism  All the chemical reactions that take place in a cell  Enzymes regulate metabolic pathways  Metabolic Pathway  Set of enzyme-catalyzed reactions that relate reactants and products (biochemical pathways)  Substrate  product = substrate  final pathway’s product  Final product can fit in to Enzyme 1 – stop reaction  What is this called?

AP Biology Metabolism  Chemical reactions of life  forming bonds between molecules  dehydration synthesis  synthesis  anabolic - consumption of energy to build complex molecules from small molecules  Glucose  starch CO 2 + H 2 O  C 6 H 12 O 6 + O 2 Photosynthesis That’s why they’re called anabolic steroids!

AP Biology Metabolism  breaking bonds between molecules  hydrolysis  digestion  catabolic reactions - release energy by breaking down complex molecules into simpler molecules.  Ex. Starch  glucose (net loss) That’s why they’re called anabolic steroids!

AP Biology Examples  dehydration synthesis (synthesis)  hydrolysis (digestion) + H2OH2O + H2OH2O enzyme

AP Biology Examples  dehydration synthesis (synthesis)  hydrolysis (digestion) enzyme

AP Biology Energy  The ability to do work  The 1 st law of Thermodynamics  Energy cannot be created or destroyed  It can only be transformed from one type into another  Heat is the ultimate form of energy – last step of transformation

AP Biology  The 2 nd law of thermodynamics  Every energy transformation increases the entropy (disorder of the universe) the entropy  K  Free Energy – The amount of energy available to a system (∆G)

AP Biology Chemical reactions & energy  Some chemical reactions net release of free energy  exergonic  Energy now available from the breakdown  digesting polymers  hydrolysis = catabolism  Spontaneous  Link for you to study at home Link for you to study at home digesting molecules= LESS organization= lower energy state -G-G

AP Biology exergonic -Spontaneous -G-G  G = change in free energy = ability to do work w/ enzyme lowers activation energy

AP Biology  Some chemical reactions require net input of energy  endergonic  building polymers  Absorbs free energy from surroundings  Net gain of energy building molecules= MORE organization= higher energy state

AP Biology Endergonic vs. exergonic reactions endergonic - energy invested - synthesis +G+G CO 2 +H 2 O A.E. from light captured Glucose Net energy captured by synthesizing glucose

AP Biology Energy & life  Organisms require energy to live  where does that energy come from?  coupling exergonic reactions (releasing energy) with endergonic reactions (needing energy) ++ energy + + digestion synthesis

AP Biology Starch Glycogen Glucose Exergonic reactions drive Endergonic Reactions (Catabolic)(anabolic) ATP Synthase – hydrogen fed into synthase, energy, happens in mitochondria, ADP  ATP

AP Biology H+H+ catalytic head rod rotor H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP synthase ATP synthase (extra for now) ATP But… How is the proton (H + ) gradient formed? ADP P +  Enzyme channel in mitochondrial membrane Enzyme channel in mitochondrial membrane  permeable to H + permeable  H + flow down concentration gradient  flow like water over water wheel  flowing H+ cause change in shape of ATP synthase enzyme  powers bonding of P i to ADP: ADP + P i  ATP

AP Biology What drives reactions?  If reactions are “downhill”, why don’t they just happen spontaneously?  because covalent bonds are stable bonds Why don’t stable polymers spontaneously digest into their monomers? starch

AP Biology Adenine Triphosphate (ATP)  ATP powers cellular work by coupling exergonic and endergonic reactions  ATP  changes the shape of a molecule  causes work  then molecule goes back to original shape  Phosphorylation – the energy from the hydrolysis of ATP is directly coupled to endergonic processes by the transfer of the phosphate group to another molecule  The recipient molecule is phosphorylated

AP Biology Can’t store ATP  good energy donor, not good energy storage too reactive transfers P i too easily only short term energy storage  carbohydrates & fats are long term energy storage ATP / ADP cycle A working muscle recycles over 10 million ATPs per second Whoa! Pass me the glucose (and O 2 (and O 2 )! ATP ADP PiPi kcal/mole cellular respiration

AP Biology 1. Reatants 2. Products 3. Activation Energy Activation 4. Transition State 5. Ea w/ enzyme 6. + or -G-G

AP Biology Enzymes  Biological catalysts  proteins (& RNA)  facilitate chemical reactions facilitate chemical reactions  increase rate of reaction without being consumed  reduce activation energy  don’t change free energy (  G) released or required  required for most biological reactions  highly specific  thousands of different enzymes in cells  control reactions of life

AP Biology Enzymes vocabulary substrate  reactant which binds to enzyme  enzyme-substrate complex: temporary association product  end result of reaction active site  enzyme’s catalytic site; substrate fits into active site substrate enzyme products active site

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  like “key fits into lock” In biology… Size doesn’t matter… Shape matters!

AP Biology 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 change shape  “conformational change”  bring chemical groups in position to catalyze reaction

AP Biology Factors that Affect Enzymes

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

AP Biology Mr Z – Draw Picture of Enzyme on board

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 coenzymes  non-protein, organic molecules  bind temporarily or permanently to enzyme near active site  many vitamins 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-CompetitiveNon-Competitive Inhibitor  Inhibitor binds to site other than active site  allosteric inhibitor binds to allosteric site allosteric inhibitor  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 – This slide is extra  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 pathwaypathway  final product is inhibitor of earlier step  allosteric inhibitor of earlier enzyme  feedback inhibition 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 Other example – insulin, oxytocin 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