Chapter 27 (continued) Specific Catabolic Pathways: Carbohydrate, Lipid & Protein Metabolism.
ENERGY Intro to Cellular Metabolism. Metabolism: Metabolism – totality of an organism’s chemical...
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Transcript of ENERGY Intro to Cellular Metabolism. Metabolism: Metabolism – totality of an organism’s chemical...
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ENERGY
Intro to Cellular Metabolism
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Metabolism: Metabolism – totality of an organism’s
chemical reactions Catabolic pathways – metabolic path that
releases energy by breaking down complex molecules into simpler molecules
Anabolic pathways – metabolic path that consumes energy to build complex molecules from simpler molecules
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Forms of Energy (capacity to cause change)
Radiant: sunlight, EM waves Chemical: Glucose, ATP, Starch Kinetic: Molecular movement (diffusion,
osmosis) Heat Mechanical: Muscle contraction
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1st Law of Thermodynamics
Energy may neither be created nor destroyed; it may only be transferred or transformed.
Thus in a closed system the total energy remains constant.
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Closed vs. Open Systems
Organisms are open systems that exchange materials with their environments
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2nd Law of Thermodynamics At every energy transfer, some energy is
lost to the system (usually in form of heat) This loss increases entropy (disorder)
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Large Scale
Energy flows into ecosystems as heat and exits as heat radiated into space
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Small Scale
Animals take in organized forms of matter and energy & replace them with less ordered forms.
Ordered Less ordered Starch Proteins catabolized CO2, H2O Lipids
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A word about “order”
Systems rich in energy are highly ordered Examples:
Complex molecules Human beings
Smaller parts (e.g. monomers of macromolecules) have less energy and are less ordered
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Spontaneous processes
Reactions that occur without outside help. Ex: water flowing downhill
Release energy For a rxn to be spontaneous, it must
increase entropy of universe
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Spontaneous reactions
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Non-spontaneous processes
Require an input of energy Ex: Synthesize a protein
Decrease entropy in a system (a protein is more ordered than it’s amino acid
monomers)
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Non-spontaneous reactions
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Gibb’s Free Energy Free energy (G) is the portion of a system’s
energy that can perform work.
Free Energy Change: ΔG = ΔH – TΔS H = total energy (enthalpy) T = degrees in K S = entropy
OR: ΔG = G(final state) – G(initial state)
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Spontaneous Rxn:
ΔG = ΔH – TΔS
For a rxn to be spontaneous, ΔG must be negative
Either decrease enthalpy (total energy) Or increase entropy (give up order)
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Endergonic vs. Exergonic
Endergonic rxn – absorbs free energy from surroundings (ΔG is positive) Creates more order (anabolic)
Exergonic rxn – releases free energy into surroundings (ΔG is negative) Creates more disorder (catabolic)
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Metabolic Equilibrium( a very, very bad thing)
Reactions in a closed system reach equilibrium ΔG will be 0; no work can be done.
A cell that reaches metabolic equilibrium is dead!
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Key to preventing equilibrium =
The product of one reaction becomes the reactant in the next. i.e. Products do not accumulate
Energy coupling: the use of an exergonic reaction (release energy) to power an endergonic (requires energy) reaction.
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Example:
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ATP! (adenosine triphosphate)
Energy source that powers cell’s activities
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