Biology 1202B Lecture Notes - Cellular Respiration, Electron Donor, Endergonic Reaction

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Published on 19 Apr 2013
Department
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
oAmount 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
oEntropy – 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)
oChange 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
oElectron donor = reducing agent, electron acceptor = oxidizing agent
oPhotosynthesis – reduction of CO2 into sugars + oxidation of H2O into O2
oRespiration (reverse reaction) – oxidizes sugars to produce CO2 and O2
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 H2O
(reverse = hydrolysis)
oExergonic hydrolysis of ATP s coupled with the endergonic process of
transferring a phosphate group to another molecule (ATP + H2O = ADP + P)
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