General Biology 2 - Energy in Life PDF

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Summary

The terms ChemotrophPhototroph reflects different ways of and obtaining __________. How do each obtain their energy? Can Chemotrophs you Identify the in this terrestrial phototrophs? ecosystem? Energy is transformed as it flows through ecosystems. Enters as radiant energy and exits as thermal energy...

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The terms Phototroph and Chemotroph reflects different ways of obtaining __________ . How do each obtain their energy? Can you Identify the phototrophs? Chemotrophs in this terrestrial ecosystem?

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• Energy important for life can exists in many forms: 1. Radiant Energy 2. Chemical Energy 3. Thermal Energy 4. Mechanical Energy 5. Electrical Energy Review: Many of these can exist as potential or kinetic energy. What is the difference?

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• Energy is transformed as it flows through ecosystems. • Enters as radiant energy and exits as thermal energy. • Processes in organisms are subject to the laws of thermodynamics.

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What is the first law of thermodynamics? Energy can be ___________ or ___________ but cannot be ___________ or ___________ . What is the second law of thermodynamics? As energy is transformed, some energy is converted to ___________ energy as the entropy (disorder) of the system ___________ . How do these laws relate to biological systems? Heat

(Unusable Energy)

Sugars

Chemical energy

(a) First law of thermodynamics

ATP (Usable Energy)

(b) Second law of thermodynamics

↑ in Entropy

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• Organisms use energy to power biological _____ . • What kinds of _____ do organisms carry out? A. Synthesizing molecules to build complex structures and to reproduce. B. Movement of the body, cells, and substances within cells. C. Transport of chemicals across the cell membrane.

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________ work ________ work

________ work 7

• Biological work is accomplished by coupling a spontaneous process to a nonspontaneous process.

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• A process is spontaneous if it proceed on their own, without any added energy.

(a) Gravitational motion

(b) Diffusion

(c) Chemical reaction 9

• The spontaneity of a process is determined by 2 factors: 1.The change in potential energy. 2.The change in the degree of order.

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1. Processes tend to be spontaneous if the end state has lower potential energy than the starting state. 2. Processes tend to be spontaneous when the end state is less ordered than the starting state. 11

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• Can we predict if a process is spontaneous or nonspontaneous? • To determine this, it’s necessary to assess the combined contributions of changes of potential energy and changes in disorder. • We do this with a quantity called Gibbs free-energy change, symbolized by DG:

DG = DH - TDS H stands for Enthalpy S represents Entropy T represents Temperature (in Kelvin). The TDS term simply means that entropy (S) becomes more important in determining free-energy change as the temperature of the molecules increase.

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• DG < 0: Process is exergonic (spontaneous) • DG > 0: Process is endergonic (nonspontaneous) • DG = 0: Process is at equilibrium 14

(a) Exergonic reaction: energy released, spontaneous

Reactants Amount of energy released (Δ ΔG < 0)

Free energy

• Exergonic Process: represents the energy available to carry out work when a process occurs.

Energy Products

Progress of the reaction

(b) Endergonic reaction: energy required, nonspontaneous Products

Free energy

• Endergonic Process: represents the energy required to carry out a process.

Amount of energy required (Δ ΔG > 0) Energy Reactants

Progress of the reaction

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• ATP hydrolysis is usually the exergonic process used to drive an endergonic process in energy coupling. • ATP acts as the energy currency in cells.

Energy can be used to power an endergonic process. 16

ΔG < 0

• Can be used to carry out work. • Proceed towards equilibrium (DG=0)

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Work is carried out

ΔG < 0

Work stops

ΔG = 0

(a) An isolated hydroelectric system A spontaneous process reaches equilibrium in a close system and work stops.

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ΔG = 0

• Forward process occurs at the same rate as the reverse process. • Le Châtelier’s Principle: Equilibrium can be disturbed (or prevented) by changing parameters. 19

CO2(g) + H2O (l) çè H2CO3 (aq) What would happen if you: 1. Remove CO2 from this system? 2. Add H2CO3?

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Add Reactants

(b) An open hydroelectric system

Work is carried out

ΔG < 0

A spontaneous process does not reach equilibrium in a open system and work continues.

Remove Products

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• Chemical reactions in cells do not reach equilibrium (DG=0). • Reactants and products are maintained at steady-state (stable) concentrations not equilibrium concentrations so reactions are exergonic (DG...