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ellie2
lesson 2
| Question | Answer |
|---|---|
| First law of thermodynamics | in any physical or chemical change, the total amount of energy in the universe remains constant, although the form of the energy may change |
| second law of thermodynamics | the total entropy of the universe is continually increasing |
| what is the difference between dynamic steady state and equilibrium? | dynamic steady state is a steady state that is far from equilibrium. maintaining this state requires the constant investment of energy. equilibrium is the state of a system in which no further net change is occurring; the free energy is at a minimum |
| is it possible to design a closed system that incorporates living organisms? | no. because a closed system is a system that exchanges energy with its surroundings, but not matter. therefore, living organisms are open systems.they exchange both matter and energy from their surroundings |
| what happens in terms of electron flow, to the reactant that is oxidized? | it loses electrons - (oxidized = loses electrons, reduced = gains electrons) |
| what are the qualities that determine the free energy (G) in a system? | (1) the enthalpy change, H, reflecting the kinds/numbers of chemical bonds and noncovalent interactions broken and formed, and (2)the entropy change, S, describing the change in the systems randomness |
| How are cells able to synthesize polymers if such reactions are thermodynamically unfavorable? | the cells couple the thermodynamically unfavorable endergonic reactions to other reactions that liberate free energy (exergonic reactions) so that the overall process is exergonic: the sum of the free energy changes is negative |
| in terms of potential energy, energy transductions, and entropy, expalin the following normal human daily activites: eating, moving, excreting. Where do the sun and ATP fit into this scheme? | |
| does the oxidation of glucose represent an increase or decrease in entropy? Does it have a positive or negative G? | oxidation of glucose represents an increase in entropy. It has a negative G of -686kcal/mol. Spontaneous rxns are always negative and always proceed with an increase in total entropy- second law of thermodynamics. |
| what are some ways of expressing a driving force on a reaction? | 1-Liberation of heat(exothemic reactions are driven) 2-Free energy-change in free energy should be negative 3-Entropy-An increase in entropy drives a reaction 4-Equilibrium shift-Removing products drives reaction |
| why are enzymes essential in biochemical reactions? | because enzymes increase the rate of specific chemical reactions without being consumed in the process |
| how do enzymes overcome activation barriers? | 1-the reactants could be exposed to heat 2- lower the activation energy barrier by breaking existing bonds and forming new ones |
| why is the option of increasing temperature to overcome these barriers not possible in living cells? | There is an optimum temperature for cells and they work best in that temperature. If you increase the temperature, proteins can denature and the organism can die |
| what would be the negative consequence to the cell of making too much of one metabolite? | the unused metabolite would accumulate in the cell & the increased conc. could inhibit or accelerate the catalytic activity of another enzyme in the pathway, slowing down or speeding up the production |
| explain how defining the "system" and "surroundings" allows living organisms to operate within the second law of thermodynamics? | constant exchange of material/energy b/w system/surroundings is how organisms create order w/in themselves.living organisms preserve internal order by taking from the surrounding (nutrients/sunlight) & returning an equal amt of energy as heat & entropy |
| what is the definition of exergonic? of endergonic? | exergonic - chemical rxn where the change in the Gibbs free energy is negative indicating a spontaneous reaction. Endergonic-unfavorable rxn where the standard change in free energy is positive & energy is absorbed. |
| from where do cells acquire their necessary free energy? why can't cells use heat as a free energy source? | heterotrophic cells acquire energy from nutrient molecules, photosynthetic cells aquire it from absorbed solar radiation. Cells cannot use heat b/c heat is not free energy. Heat can only do work as it passes to a zone/object at a lower temperature |
| what exactly does "at equilibrium" mean in terms of (a) the rate of both the forward and reverse rxn and (b) the concentrations of the reactants and products? | at the equilibrium concentration of reactants and products, the rates of the forward and reverse reactions are exactly equal and no further net change occurs in the system |
| what reaction conditions are used to measure the standard free energy change, G' | standard conditions |
| if, at equilibrium, the concentration of products is greater than the concentration of reactants, is the G' positive or negative? What can you say about the value of K'eq? | positive, which means K'eq is <1.0 |
| What is the definition of entropy, and enthalpy? | Entropy- quantitative expression for the randomness or disorder in a system Enthalpy- the heat content of the reacting system. it reflects the number and kinds of chemical bonds in the reactants and products |
| What is the definition of Gibbs free energy? | Gibbs free energy - the amount of energy capable of doing work during a rxn at a constant temperature and pressure |
| what does it mean when G' is negative? | When G' is negative = the product contains less free energy then the reactant and the rxn will proceed spontaneously under standard conditions. |
| What does it mean when G' is positive? | A positive G' means that the product of the rxn contains more free energy then the reactants, and this rxn will go in the reverse direction if we start with 1.0M concentration of all components |
| what effect does the presence of an enzyme have on the G' of the rxn it catalyzes? | an enzyme provides an alternative rxn pathway w/ a lower activation energy. Enzymes increase the rate at which a rxn proceeds in the direction dictated by thermodynamics |
| under what circumstances can G be negative if G' is positive? Could cells use this strategy to drive thermodynamically unfavorable rxns? | A rxn w/ a positive G' can go in the forward direction if G is negative. this is only possible if the RT is negative and has a larger absolute value then G'. yes cells could use this strategy |
| What does G tell us about a rxn and what does G' tell us? | G' tells us which direction & how far a rxn must go to reach equilibrium. G is a function of reactant & product conc & temp during the rxn. spontaneity of a rxn is determined by G. |
| does the value of G' (or G) tell you anything about (a) the rate at which a rxn occurs or (b) the pathway by which the final product is formed? | the value of G tells you which direction the reaction will occur. Negative rxns proceed forward & are spontaneous.Positive are not spontaneous & likely will not happen |
| how can the coupling of a thermodynamically unfavorable reaction to a thermodynamically favourable reaction increase the K'eq of the overall equation? | b/c in thermodynamic calculations, the K'eq for the overall rxn is the product of the individual K'eq values for the two reactions. Equilibrium constants are subject to multiplication |
| explain why relatively small changes in G' correspond to large changes in K'eq? | G' of a rxn=an alt. math. way of expressing its equilibrium constant(EC).for a given rxn if EC= 1,G'is 0.If K'eq of a rxn is>1, its ΔG°' is -. If K'eq is<1, ΔG°' is +. B/c the relation b/w ΔG°'&K'eq=mathematical,small changes in ΔG°'=large changes in K'eq |
| what physical and chemical factors contribute to the free energy change of ATP hydrolysis? | ATP hydrolysis is the rxn by which energy that has been stored & transported in the high-energy phosphoanhydridic bonds in ATP is released. The product is ADP & an inorganic phosphate, Pi. ADP can be further hydrolyzed to give energy, AMP, & another Pi. |
| how do ΔG, ΔG°', and ΔGp differ? | ΔG = ΔH - TΔS ΔG°'= -RT1nKeq ΔGp = A quantitative measure of the energy status of a cell: [ATP]/[ADP][Pi] |
| what are the main reasons for the high ΔG°' values for hydrolysis for phosphoenolpyruvate, 1,3-bisphophoglycerate, phosphocreatine, acetyl CoA, and other similar compounds? | Because the product of hydrolysis can exist in either enol or keto form, whereas the reactant has only one form (enol). The product is stabilized relative to the reactant. |
| why is the "single arrow" representation of the conversion of ATP to ADP and Pi deceiving? | b/c more then 1 step takes place.Part of the ATP molecule is transferred to a substrate molecule becoming covalently attached to the substrate & raising its free energy content.Then the phosphate containing moiety is displaced, generating Pi, PPi or AMP |
| the reactions that produce conformational changes linked to ATP (or GTP) hydrolysis are different from other ATP-driven reactions. Explain. | |
| What is the relative position of ATP in the hierarchy of compounds with phosphoryl group transfer potentials? | ATP has a phosphoryl transfer potential that is intermediate among the biologically important phosphorylated molecules. This intermediate position enables ATP to function efficiently as a carrier of phosphoryl groups. |
| What is the difference b/w thermodynamic stability (or instability) and kinetic stability? | Kinetic-how slowly something reacts Thermodynamic-the energies involved. ex: aluminium is kinetically more stable than iron in damp air bc it won't rust but thermodynamically less stable bc if it oxidises it would give out more energy. |
| why are adenylylation reactions so thermodynamically favorable? | b/c they provide a "push" of energy |
| what are the similarities and differences b/w the assembly of DNA and RNA from their component nucleotides and the activation of fatty acids and amino acids? | precursors for DNA and RNA synthesis are nucleoside triphosphates. the activation of amino acids for protein synthesis involves the donation of adenyly groups from ATP. |
| what is the specific role of ATP in the transport of solutes across membranes (ie: what does the transfer of a phosphoryl group from ATP to the pump protein accomplish)? | supplying energy |
| what are the cellular roles of nucleoside diphosphate kinase, adenylate kinase, and creatine kinase? Why are they so important? | they carry phosphoryl groups from ATP to the other nucleotides, and catalyze the reaction to the right. this results in an accumulation of ADP |
| why is polyP an interesting molecule to those who study cellular evolution? | it serves as a phosphagen which is a reservoir of phosphoryl groups that can be used to generate ATP. it has the same potential as PPi and can serve as the energy source for active transport of H+ across the membrane of plant cells |
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