4 Organisms and Energy Three types of energy organisms use: Light – photons, wavesElectrons – potential energy in chemical bondsGradients – ‘push’ protons across a membrane and let them flow back
5 Learning Objectives:1.B.1.a – Organisms share many conserved core processes and features and are widely distributed among organisms today.Metabolic pathways are conserved across all DomainsInterpreted as evidence of evolution (descent with modification)
6 Shared Metabolic Processes and Features All cells:Break and form chemical bondsUse ATPMany prokaryotes and all eukaryotes possess cytochrome cAlmost all cells do aerobic respiration w/ETCHave similar enzymes for metabolism
7 2. A. 1 – All Living Systems Require Constant Input of Free Energy 2.A.1 – All Living Systems Require Constant Input of Free Energy. Life Requires a Highly Ordered SystemOrder is maintained by constant input of free energyLoss of order or free energy results in deathIncreased disorder and entropy are offset by biological processes that maintain or increase order
8 Living systems do not violate the Second Law of Thermodynamics which states that entropy increases over time.Order is maintained by coupling reactions that increase entropy (and so have negative changes in free energy) with those that decrease entropy (and so have positive changes in free energy)Energy input must exceed free energy lost to entropy to maintain order and power cellular processesEnergetically favorable exergonic reactions such as ATP-ADP, have a negative change in free energy can be used to maintain or increase order in a system by being coupled with reactions that have positive free-energy change.
9 Thermodynamics 1st law – energy cannot be created or destroyed. Can be transformed, but does not go away2nd law – Entropy; energy becomes less usable as it is transformed.Lost as unusable heat.Entropy increases as energy is transferred.Stuff goes from order to disorder.
10 Thermodynamics – ‘Free’ Energy ‘Free’ = ‘usable’Organisms absorb usable energy (free energy) from light.They convert light (kinetic energy) to potential energy in chemical bonds (C-H); entropy of the environment increases.Cells maintain their organization by increasing the entropy of the universe (Earth).
12 Gibbs “Free” Energy Δ G = ΔH – TΔS G - Gibbs “free” energy H – Enthalpy (the amount of usable energy inthe system)T – Temperature in Kelvin (273 + C⁰)S - Entropy (disorder created by somethingbeing broken down)Usable energy = total energy – T x ‘lost’ energyYoutube – Gibbs free energy; Bozeman
13 Unstable (Capable of work) vs. Stable (no work) G < 0G = 0A closed hydroelectric system
14 Catabolism (Hydrolysis Reaction) ReactantsAmount ofenergyreleased(G < 0)Free energyEnergyProductsProgress of the reactionExergonic reaction: energy released
15 Anabolism (Dehydration Synthesis) ProductsAmount ofenergyrequired(G > 0)Free energyEnergyReactantsProgress of the reactionEndergonic reaction: energy required
16 Practice, Practice, Practice An experiment determined that when a protein unfolds to its denatured (D) state from the original folded(F) state, the change in Enthalpy is ΔH = H(D) – H(F) = 56,000 joules/mol. Also the change in Entropy is ΔS = S(D) – S(F) = 178 joules/mol. At a temperature of 20⁰C, calculate the change in Free Energy ΔG, in j/mol, when the protein unfolds from its folded state. Show all your work and circle your final answer.Is this a spontaneous or non-spontaneous reaction?
18 Energy CouplingTo maintain organization, energy input must be greater than the free energy lost to entropy.Energy coupling – couple reactions that increase entropy (exergonic; negative changes in free energy) with those that decrease entropy (endergonic; positive changes in free energy)Ex. ADP-ATP cycleG < 0G > 0
19 Potential vs Kinetic Energy Potential energy - storedChemical bonds of electrons (C-H)Identify potential and kinetic energy in the pictureShort polymerUnlinked monomerDehydration removes a watermolecule, forming a new bondLonger polymerDehydration reaction in the synthesis of a polymer
20 Chemical Reactions Two kinds of reactions: Exergonic – net release of energyFire, respirationEndergonic – net absorption of energyPhotosynthesisHydrolysisDehydration synthesis
21 Metabolism – Types of Reactions Anabolism - build upStore energy by assembling macromolecules (photosynthesis)EndergonicCatabolism - break downRelease energy by breaking down molecules (digestion, respiration)Exergonic
22 Activation Energy Reactions are random collisions Spontaneous, exergonic reaction; ΔG < 0Most reactions require activation energy
23 Activation Energy Cells can only tolerate certain conditions Not too hot, low electrical charge (why?)Cells need chemical reactions to be at low activation energyCatalyst – lowers activation energyEnzymes – biological catalysts
24 Rate of Reactions in Cells Three factors affect rate of reaction in cells:Temperature – affects the speed at which molecules can collide (fast or slowly)Energy provided by the cellEnzymes - catalysts
25 Enzymes Catalysts – reduce activation energy** Globular proteins (700) Specific conformational shape**Only catalyze one specific reactionAnabolic or catabolicCatalase catalyzes 40 million reactions per second
26 Transition state - reactants absorb energy ?Endergonic or exergonic?***Transition state - reactants absorb energy
27 Progress of the reaction .Course ofreactionwithoutenzymeEAwithoutenzymeEA withenzymeis lowerReactantsFree energyCourse ofreactionwith enzymeDG is unaffectedby enzymeProductsProgress of the reaction
28 Enzymes Substrate – reactant enzyme acts upon Active site - area on the enzyme where the substrate attachesGroove or pocket created by the specific folding of proteinsSecondary, tertiary and/or quaternary
29 How Enzymes Work ‘Lock and Key’ = specificity Induced fit model - enzyme changes shape when the substrate attaches to the active site making it easier for bonds to form or break
30 Factors That Affect Enzyme Activity Correct environmental conditionspH, heatCofactorsInhibitors
31 Correct Environmental Factors Denature the enzyme (protein)Heat, pH, salinityWhy?
32 Competitive Inhibition Competitive inhibitors - resemble substrate, block active siteCyanide is a competitive inhibitor for catalase
33 Allosteric ControlAllosteric control – the shape of an enzyme’s active site is controlled at another place on the enzymeAllosteric site has to be activated, (may be inhibited)
34 Feedback InhibitionIsoleucine – allosteric inhibitorFeedback Inhibition - end product of the pathway inhibits the pathway****Prevents cells from wasting resources
35 Structure and Metabolism Cells are organizedMulti-enzyme complex - enzymes are positioned in a membraneInner membrane of mitochondria, chloroplasts
36 Enzyme CooperativityCooperativity - one substrate molecule can activate all other subunits of an enzymeOnly requires a small concentration of substrate to activate enzymePhosphofructokinaseHemoglobin
37 Organisms use free energy to maintain organization, grow and reproduce: Use various strategies to regulate temperature.Endothermy – use thermal energy to maintain homeostasis.Ectothermy – use external temperature to regulate and maintain temperatureElevated floral temperatures in some plants.
38 Relationship between metabolic rate per unit body mass and the size of multicellular organisms Generally, the smaller the organisms, the higher the metabolic rate.Reproduction and rearing of offspring requires more free energy than just maintenance and growth.Different strategies in response to energy availability.Seasonal reproduction in animals and plantsLife-history strategy (annuals, biennials, etc.)Diapause – eggs and/or development stop due to adverse conditions (insects, plants)
40 Energy Changes Affect Populations Changes in free energy availability can result in changes in population size and or disruptions to an ecosystemChange in the producer level can affect the size and number of other trophic levelsChange in energy resource (sunlight) can affect all trophic levels