Honors Biology Chapter 6 Enzymes PDF

Metabolism & Enzymes Chapter 6 Honors Biology  Flow of energy through life ▪ Life is built on chemical reactions ◆ transforming energy from one form to organic molecules → another ATP & organic molecul...

Metabolism & Enzymes Chapter 6 Honors Biology  Flow of energy through life ▪ Life is built on chemical reactions ◆ transforming energy from one form to organic molecules → another ATP & organic molecules su organic molecules → n ATP & organic molecules solar energy → Honors ATP &Biology organic molecules  Metabolism ▪ Chemical reactions of life ◆ forming bonds between molecules ▪ dehydration synthesis ▪ synthesis ▪ anabolic reactions ◆ breaking bonds between molecules ▪ hydrolysis ▪ digestion ▪ catabolic reactions Honors Biology  Examples ▪ dehydration synthesis (synthesis) enzyme ▪ hydrolysis (digestion) enzyme Honors Biology  Chemical reactions & energy ▪ Some chemical reactions release energy ◆ exergonic ◆ digesting polymers ◆ hydrolysis = catabolism ▪ Some chemical reactions require input of energy ◆ endergonic ◆ building polymers ◆ dehydration synthesis = anabolism Honors Biology  Endergonic vs. exergonic reactions exergonic endergonic - energy released - energy invested - digestion - synthesis +Δ G - ΔG ΔG Honors Biology = change in free energy = ability to do  Energy & life ▪ Organisms require energy to live ◆ where does that energy come from? ▪ coupling exergonic reactions (releasing energy) with endergonic reactions (needing energy) ener + + gy digestion synthesis ener + + gy Honors Biology  Living economy ▪ Fueling the body’s economy ◆ eat high energy organic molecules ▪ food = carbohydrates, lipids, proteins, nucleic acids ◆ break them down ▪ catabolism = digest ◆ capture released energy in a form the cell can use ▪ Need an energy currency ◆ a way to pass energy around ◆ need a short term energy storage molecule ATP Honors Biology  ATP ▪ Adenosine Triphosphate ◆ modified nucleotide ▪ nucleotide = adenine + ribose + Pi → AMP ▪ AMP + Pi → ADP ▪ ADP + Pi → ATP ◆ adding phosphates is endergonic high energy bonds Honors Biology  How does ATP store energy? O– O– O– O– O– – O P –O O– P –O O––P OOP––O O– P O– O O O O O AMP ADP ATP ▪ Each negative PO4 more difficult to add ◆ a lot of stored energy in each bond ▪ most energy stored in 3rd Pi ▪ 3rd Pi is hardest group to keep bonded to molecule ▪ Bonding of negative Pi groups is unstable ◆ spring-loaded ◆ Pi groups “pop” off easily & release energy Honors Biology Instability of its P bonds makes ATP an excellent energy donor  How does ATP transfer energy? O– O– O– O– 7.3 – O P –O O– P –O O– P O– – O P O– + ene O O O O rgy ADP ATP ▪ ATP → ADP ◆ releases energy ▪ ∆G = -7.3 kcal/mole ◆ can fuel other reactions ▪ Phosphorylation ◆ released Pi can transfer to other molecules Honors Biology▪ destabilizing the other molecules  ATP / ADP cycle Can’t store ATP AT ▪ too reactive P ▪ transfers Pi too respiration 7.3 kcal/mole easily ▪ only short term A energy storage D + P ▪ carbohydrates & P fats are long term A working muscle recycles over energy storage 10 million ATPs per second Honors Biology  Activation energy ▪ Breaking down large molecules requires an initial input of energy ◆ activation energy ◆ large biomolecules are stable ◆ must absorb energy to break bonds cellulose energy CO2 + H2O + heat Honors Biology  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 Honors Biology  Reducing Activation energy ▪ Catalysts ◆ reducing the amount of energy to start a reaction uncatalyzed reaction catalyzed reaction NEW activation energy reactant product Honors Biology  Enzymes ▪ Biological catalysts ◆ proteins (& RNA) ◆ facilitate chemical reactions ▪ increase rate of reaction without being consumed ▪ reduce activation energy ▪ don’t change free energy (ΔG) released or required ◆ required for most biological reactions ◆ highly specific ▪ thousands of different enzymes in cells ◆ control reactions of life Honors 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 active site substrate products enzyme Honors Biology  Properties of enzymes ▪ Reaction specific ◆ each enzyme works with a specific substrate ▪ chemical fit between active site & substrate ⬥ H bonds & ionic bonds ▪ Not consumed in reaction ◆ single enzyme molecule can catalyze thousands or more reactions per second ▪ enzymes unaffected by the reaction ▪ Affected by cellular conditions ◆ any condition that affects protein structure ▪ temperature, pH, salinity Honors Biology  Naming conventions ▪ Enzymes named for reaction they catalyze ◆ sucrase breaks down sucrose ◆ proteases break down proteins ◆ lipases break down lipids ◆ DNA polymerase builds DNA ▪ adds nucleotides to DNA strand ◆ pepsin breaks down proteins (polypeptides) Honors Biology  Factors Affecting Enzyme Function ▪ Enzyme concentration ▪ Substrate concentration ▪ Temperature ▪ pH ▪ Salinity ▪ Activators ▪ Inhibitors Honors Biology catalase  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 reaction rate Honors Biology enzyme concentration  Enzymes and temperature ▪ Different enzymes function in different organisms in different environments hot spring human enzyme bacteria enzyme reaction rate 37°C 70°C Honors Biology temperature (158°F)  Factors affecting enzyme function ▪ pH ◆ changes in pH ▪ adds or remove H+ ▪ disrupts bonds, disrupts 3D shape ⬥ denatures protein ◆ optimal pH? ▪ most human enzymes = pH 6-8 ⬥ depends on localized conditions ⬥ pepsin (stomach) = pH 2-3 ⬥ trypsin (small intestines) = pH 8 Honors Biology 0 1 2 3 4 5 6 7 8 9 10 11  Compounds which help enzymes ▪ Activators Fe in hemoglobin ◆ cofactors ▪ non-protein, small inorganic compounds & ions ⬥ bound within enzyme molecule ◆ coenzymes ▪ non-protein, organic molecules ⬥ bind temporarily or permanently to enzyme near active site ▪ many vitamins Mg in ⬥ NAD (niacin; B3) chlorophyll ⬥ FAD (riboflavin; B2) ⬥ Coenzyme A Honors Biology  Allosteric regulation ▪ Conformational changes by regulatory molecules ◆ inhibitors ▪ keeps enzyme in inactive form ◆ activators ▪ keeps enzyme in active form Conformational Honors Biology changes Allosteric regulation  Any Questions? 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