Enzymesproteins (and RNA) | organic catalysts that lower the required activation energy to get reactants to products | facilitate chemical reactions: | ~ increase rate of reaction without being consumed | ~ reduce activation energy | ~ do not change free energy released or required | 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 actives site |
pHchanges in pH: | ~ adds or removes H+ | ~ disrupts bond, disrupts 3D shape | ~ disrupts attractions between charged amino acids | ~ affects 2' and 3' structure | ~ denatures protein |
Activatorscofactors: | coenzymes: | small, inorganic compounds and ions | organic compounds | binds with enzyme | bind to enzymes near active site | Mg, K, Ca, Zn, Fe | vitamins (NAD, FAD, Coenzyme A) |
Allosteric Regulationconformational changes by regulatory molecules | inhibitors: keeps enzyme in inactive form | activators: keeps enzyme in active form |
Metabolic Pathwayscatabolic pathways: | metabolic pathways: | release energy | consume energy | cellular respiration | photosynthesis |
Transformation of Energysunlight -> chemical bonds during photosynthesis |
Exergonic vs. Endergonic Reactions| | exergonic: | endergonic: | positive / negative G free energy: | negative | positive | released / absorbed | released | absorbed | cellular respiration / photosynthesis | cellular respiration | photosynthesis | uphill / downhill | downhill | uphill | spontaneous | spontaneous | not spontaneous |
Endothermsregulate internal body temperatures through metabolism | balancing heat loss and gain | five adaptations help animals thermoregulate: | 1) insulation | 2) circulating adaptations | 3) cooling by evaporative heat loss | 4) behavioral responses | 5) adjusting metabolic heat production |
Overview of Photosynthesis
Glycolysislocation: | cytoplasm | reactants: | ~ glucose | | | ~ 2 ADP +2 Pi | | | ~ 2 NAD+ | products: | ~ 2 pyruvate | | | ~ 2 ATP | | | ~ 2 NADH | | | ~ 2 H2O | transfer of energy: | NADH (electrons and Hydrogen) <- C6H12O6 -> ATP | purpose: | ~ convert glucose to pyruvate | | | ~ initial breakdown of sugar | | | ~ generating ATP | | | ~ shuttling e- and H+ to ETC |
REDOX Reactionsmolecular exchange of an electron | oxidation: lose electrons | reduction: gain electrons |
Photosynthesistransformation of solar light energy trapped by chloroplasts into chemical bond energy stored in sugar and other organic molecules | 1) synthesizes energy rich molecules | 2) uses CO2 as carbon source | 3) directly or indirectly supplies energy | CO2 + H2O + sunlight -> C6H12O6 + O2 |
Steps of Light Reactions1) H2O splits | ~ H+: pump into thylakoid out of ATP synthase | ~ e-: 2 ETCs | ~ O2: released out of stomata | 2) light excites e- in Photosystem II | 3) e- to primary electron acceptor (PEA) | 4) the e- travels down the ETC and replaces the e- from Photosystem I | 5) the e- travels down another ETC and combines with NAHP+ | meanwhile... | ~ energy from 1st ETC is used to pump H+ into the thylakoid space | ~ a proton gradient forms and H+ leave through ATP synthase | ~ H+ combines with e- and NADP+ to form NADPH | ~ ATP synthase generates ATP |
| | Properties of Enzymesreaction specific: | ~ each enzyme works with a specific substrate chemical fit between active site and substrate | ~ H bonds and ionic bonds | not consumed in reaction: | ~ single enzyme molecule can catalyze thousands or more reactions per second | ~ enzymes are unaffected by the reaction | affected by cellular conditions | ~ ex: temperature, pH, salinity, etc. |
Substrate Concentrationas substrates increase, reaction rate increases and levels off | more substrate = more frequently collide with enzyme | the reaction levels off because... | ~ all enzymes have active site engaged | ~ enzyme is saturated | ~ maximum rate of reaction |
Factors that Affect Enzyme Structure
Competitive Inhibitorsinhibitor competes with active site | substrate cannot bond | can overcome with substrate saturation | penicillin (competes with bacterial enzyme that builds cell wall) | directly blocks active site |
Energythe ability to do work | kinetic energy: | potential energy: | energy of motion | energy of position | heat | water behind a dam | light energy | chemical energy stored in cells |
Free Energy and Equilibriumfree energy: energy available to do work | free energy decreases when reactions proceed toward equilibrium |
Biosynthesisbuilding complex molecules out of simple molecules | amino acids -> proteins | glucose -> glycogen |
Ectothermsdo not regulate internal body temperature | rely on environmental heat sources | less respiration/food |
Cellular Respirationcatabolic | C6H12O6 + O2 -> CO2 + H2O + energy | steps: | 1) gylcolysis | 2) intermediate step | 3) citric acid cycle | 4) oxidative phosphorylation |
Intermediate Steplocation: | mitochondrial matrix | reactants: | 2 pyruvate | products: | ~ acetyl CoA | | | ~ 2 NADH | | | ~ 2 CO2 | transfer of energy: | pyruvate (sugar) -> NADH (e- and H+) | purpose: | convert pyruvate into more reactive Acetyl CoA |
Oxidative Phosphorylationlocation: | ~ inner membrane of mitochondria (ETC) | | | ~ inner membrane spare (chemiosmosis) | reactants: | ~ NADH | | | ~ FADH2 | | | ~ ADP+P | | | ~ O2 | products: | ~ NAD+H | | | ~ FAD+H | | | ~ ATP | | | ~ H2O | transfer of energy: | NADH/FADH2 -> proton gradient -> ATP synthase -> ATP | purpose: | use REDOX reactions to make a large amount of ATP (34) |
producersautotrophic nutritional: nutritional made of synthesizing organic molecules from inorganic raw materials | photoautotrophs: uses light energy | chemoautotrophs: oxidation of inorganics for energy |
Chloroplastsite of photosynthesis | double membrane system | thylakoids: flattened photocenters | granum: stacks of thylakoids | stroma: fluid outside thylakoid |
Calvin Cyclelocation: stomata | production of sugar | recognition of RUBP | reactants: CO2, NADPH, ATP | products: C6H12O6, NADP+, ADP+Pi, G3P |
Pathways of Photosynthesisnoncyclic photophosphorylation produces ATP and NADPH | cyclic photophosphorylation is ATP production | calvin cycle consumes more ATP than NADPH |
| | Induced Fit"lock and key" | 3-D structure of enzyme fits substrate | substrate binding cause enzyme to change shape leading to a tighter fit | "conformational change": slight change in shape | bring chemical groups in position to catalyze reactions |
Enzyme Concentrationas enzymes increase, reaction rate increases | more enzymes = more frequently collide with substrates |
Temperatureoptimum temperature: | ~ as temp increases, reaction rate increases | ~ greater number of molecular collisions | cold temperature: | ~ molecules move slower | ~ decrease collisions between enzymes and substrates | heat (beyond optimum) | ~ increased energy level disrupts weak bond in 2' and 3' structure | ~ denaturation: loses 3D shape |
Noncompetitive Inhibitorsinhibitor binds to allosteric site (not active site) which changes the shape of the active site | ex: anti-cancer drugs, cyanide, poisoning, DDT |
Competitive vs. Noncompetitive Inhibitors
Thermodynamicsstudy of energy transformation | first law: energy of the universe is constant | second law: every process increases the entropy of the universe | entropy: "quantity of energy in universe is constant, but quality is not" |
ATP Powers Cellular Workcoupling endergonic/exergonic reactions | energy coupling: phosphorylated intermediates; regeneration of ADP to ATP | 3 main types of work | 1) mechanical work (motor protein) | 2) transport work (Na/K pump) | 3) chemical work |
Size and Metabolic ratelarger mammals have more body mass and require more chemical energy (higher BMR) | smaller animals require more kcal/gram, have greater rate of O2 delivery, higher breathing rate | increase activity -> increase metabolic rate -> more ATP |
Overview of Cellular Respiration
Citric Acid Cyclelocation: | mitochondrial matrix | reactants: | ~ acetyl CoA | | | ~ citric acid | | | ~ ADP + Pi | | | ~ NAD+ and FAD | products: | ~ oxaloacetate | | | ~ ATP | | | ~ NADH and FADH2 | | | ~ CO2 | transfer of energy: | NADH and FADH2 (e- and H+) <- citric acid -> ATP | purpose: | ~ complete the oxidation of glucose | | | ~ producing NADH/FADH2 (e- and H+) | | | ~ ATP |
Phosphorylationsubstrate-level: ATP is synthesized by enzymes | oxidative: ATP is synthesized by an ETC and chemiosmosis |
Fermentationanaerobic process (no O2) | produces small amounts of ATP | regenerates NAD+/NADH | alcoholic fermentation | ~ yeast/bacteria | ~ produces CO2 and alcohol | lactic acid | ~ human muscles | ~ yogurt | ~ produces lactic acid |
Consumersheterotrophs: acquire organics to create energy from other creatures | ~ consumers | ~ decomposers |
Light Reactionsoccurs in the thylakoid | splitting of water | generation of ATP and NADPH | reactants: H2O, NADP+, ADP+Pi | products: O2, NADPH, ATP |
Steps of Calvin Cycle1) carbon fixation | ~ ribulose biphosphate: RuBP | ~ rubisco: RuBP carboxylase: most abundant protein | 2) reduction | ~ adding H+ and e- from NADPH to CO2 to make sugar | 3) regeneration | ~ G3P -> RuBP |
Alternative Pathways of Carbon Fixationphotorespiration: fixing oxygen rather than CO2 | C3 plants: | ~ hot/dry days | | | ~ stomata close (prevents H2O, inc CO2, dec O2) | C4 plants: | ~ spatial separation of calvin cycle into bundle sheath cell | | | ~ PEP carboxylase initially captures CO2 | CAM pathways: | ~ temporal separation | | | ~ takes in CO2 at night |
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