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Summary 3-Bioenergetics.doc

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Biology 1202B
Richard Gardiner

Bioenergetics Summary Definition • Study of energy in living systems and the organisms that utilize it • Potential Energy – energy that matter occupies because of its position • Kinetic Energy – energy in the process of doing work (energy of motion) Systems • Isolated – no energy/matter is transferred between system and surrounding • Closed – energy can be transferred but matter cannot • Open – both energy and matter can be exchanged with environment Laws of Thermodynamics • First: Energy cannot be created or destroyed, only converted to other forms o Amount of energy in the universe always remains constant • Second: All energy transformations are inefficient because every reaction result in an increase in entropy and the loss of unstable energy as heat o Entropy – amount of disorder in a system Biological Work • Entropy – energy that is no longer available to perform useful work (quality of heat flowing between two bodies)  nature tends to move from order to disorder in isolated systems • Free Energy – part of a system’s total energy that can perform work when temp is constant (G) o Change in free energy (from one state to another): ΔG = ΔH -TΔS Types of Reactions • Endergonic – nonspontaneous/requires a net input of energy (ΔG > 0)  e.g. photosynthesis • Exergonic – spontaneous/releases energy (ΔG < 0)  e.g. cellular respiration • Coupled Reactions – use exergonic processes to drive endergonic ones (overcome energy barrier) • Redox Reactions – involve the transfer of one more electrons from one reactant to another o Electron donor = reducing agent, electron acceptor = oxidizing agent o Photosynthesis – reduction of CO into sugars + oxidation of H O into O 2 2 2 o Respiration (reverse reaction) – oxidizes sugars to produce CO and 2 2 Cellular Metabolism • Definition – sum of total chemical activity of all cells (2 types) • Anabolic –consumes energy to build complicated molecules from simpler ones (photosynthesis) • Catabolic – releases energy by breaking down complex molecules into simpler ones (respiration) • Anabolic (synthesis) + catabolic (breakdown) = metabolism Biological Organic Molecules (composed of subunits/building blocks) • Monomers combine to make polymers (large organic molecules are called macromolecules) • Dehydration Synthesis – combining/exchange reaction with removal of H O 2 (reverse = hydrolysis) o Exergonic hydrolysis of ATP s coupled with the endergonic process of transferring a phosphate group to another molecule (ATP + H O = A2P + P) Bioenergetics Summary energy coupling Chemistry in Cell • Factory- sends chemicals through pipes/valves (complex and hard to miniaturize) • Cell – reactant and products are in the same space (chemicals interact by random collisions) Enzymes • Spontaneous chemical reactions may still occur very slowly (enzymes speed up rate as catalysts) o Catalyst – chemical agent that changes the rate of a reaction with being consumes • In every reaction bonds must break (requires energy) and new one must f
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