BIOL 215 Exam 2(Graded A+ actual test)

BIOL 215 Exam 2 Define 'energy'. - -The capacity to do work (to cause change) Compare potential energy and kinetic energy. Classify different energy forms into one of these two categories. - Potential Energy = stored energy 1. Chemical Energy: E stored in bonds of atoms and molecules 2. Concentration Gradient: concentration differences across membrane 3. Gravitational Energy: E of position or place 4. Stored Mechanical Energy: E stored in objects by application of a force Energy Energy = motion 1. Electrical Energy: movement of charged particles 2. Radiant Energy: electromagnetic E that travels in transverse waves 3. Thermal Energy: heat=internal E in substances 4. Motion Energy: movement of objects/substances from one place to another 5. Sound: movement of E through substances in longitudinal compression/rarefaction waves Explain why cells need energy? Describe the types and examples of cellular work. - -All living systems require an ongoing supply of energy 6 Categories of Change Require Cellular Energy 1. Synthetic work 2. Mechanical work 3. Concentration work 4. Electrical work 5. Generation of heat 6. Generation of light Explain how energy and matter are used in the biosphere. Specifically explain this statement: "Energy flows through the biosphere while matter is recycled". - Energy Flows Through the Biosphere: -Flow from sun to earth -Light E captured by phoautotrophs, used to convert inorganic C into organic C -Some E lost as heat -Chemotrophs & autotrophs convert organic C into usable E -Some E lost as heat Matter Recycled: -Between phototrophs and autotrophs and vice versa Phototrophic E Conversion: -Plants, and other photoautotrophs, have the amazing ability to convert light E into chemical E -This conversion also releases O2 gas, which transformed earth's atmosphere and allows us to breathe Define an organism based on its energy -converting abilities (e.g. autotroph, heterotroph, chemotroph, phototroph). - -Autotroph: organism that produces organic compounds from inorganic molecules -Heterotroph: organism that produces organic compounds starting from other organic molecules -Phototroph: able to capture light E and transform it into chemical E -Chemotroph: obtains energy by oxidizing chemical bonds in molecules Define 'thermodynamics'. - -The study of energy transformations -Cells/organisms extract E and use it to perform work Interpret the first law and second law of thermodynamics. Provide examples to illustrate these laws. - First Law of Thermodynamics: -E can be transferred and transformed -E cannot be created or destroyed -Ex: Potential E in food is converted to kinetic E of movement Second Law of Thermodynamics: -Every energy transfer of transformation increases the entropy (disorder) of the universe -During every E transfer, some E is unusable, often lost as heat -Ex: Transformation of potential E (chemical) to kinetic E (motion) increases disorder of the universe (release of heat) Define free energy. Define a 'spontaneous' process. - Free Energy: -Measure of thermodynamic spontaneity of a system -Amount of E available to do work -Looking at change in system from start to finish (State function) Tells us: -Whether a process can occur (possibility) -To what extent (directionality) -Does not say if it will actually occur Spontaneous Process: -Process that occurs without external E input -Based on the change of a system from start to finish -Spontaneous does not indicate anything about rate -Naturally occurs toward equilibrium What does deltaG tell us about a system? What does it mean if deltaG is zero? - -Negative: Spontaneous (exergonic) -Positive: Non -spontaneous (endergonic) -Zero: System has reached equilibrium; most stable state Tells us the amount of E available to do work Interpret the meaning of the following equation: ∆G = ∆H - T∆S. Explain how each variable influences the spontaneity of a system. - deltaH = change in enthalpy deltaS = change in entropy T = Temperature (Kelvins) DeltaH: -Negative = exothermic, Q is released, favorable -Positive = endothermic, Q is absorbed, unfavorable DeltaS: -Positive = more disordered, favorable -Negative = more ordered, unfavorable Be able to determine for given conditions whether a reaction can proceed spontaneously. - -
Energy is released -E Reactants > E Products Understand the equilibrium constant of a chemical reaction and define its relationship to free energy. - -Ratio of [product] to [reactant] at equilibrium -Greater than 1: more products -Less than 1: more reactants At equilibrium: -Rate of forward reaction = rate of reverse reaction -No net change in [R] or [P] -deltaG = 0 Using Keq: 1. Qualitatively interpret Keq: can determine if products or reactants are favored by simply looking at magnitude fo Keq 2. Predict direction of reaction of a system not at equilibrium: deltaG measure of how far system lies from equilibrium Interpret a free energy diagram - -Anything deviating from equilibrium is unstable -Requires input of E to be maintained -System 'wants' to move towards equilibrium -Wants to be in most stable state -Systems will react spontaneously toward equilibrium Describe the activation energy barrier for a reaction. How does EA influence the rate of a reaction? - Activation Energy: -Minimum amount of E reactants must have in order for a reaction to take place