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Energy, Catalysis and Biosynthesis
Complexity of metabolism
Metabolism
*catabolism
*anabolism
*potential energy
Conservation of Energy
Energy is defined as the capacity to perform work.
Kinetic energy is the energy of motion.
Potential energy is stored energy.
Free energy, stability, and change
Free energy
Change in free energy = ∆G
Gravitational
Motion
Diffusion
Chemical
Reaction
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Free energy, stability, and change
Equilibrium
*chemical equilibrium
∆G = 0, no net change in the system
Chemical reactions with free energy changes:
*energetically unfavorable
*energetically favorable
Metabolic Disequilibrium
*Multistep open hydroelectric system
Enzymes
– Metabolism is the total of all chemical reactions in an
organism.
– Most metabolic reactions require the assistance of
enzymes, proteins that speed up chemical reactions.
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Activation Energy
– Activation energy
• Activates the reactants
• Triggers a chemical reaction
Energy level
Activation
energy barrier
Reactant
Products
Enzymes
Enzymes lower the barrier of EA
Energy leve
el
Enzyme
Activation
energy barrier
reduced by
enzyme
Reactant
Products
(b) With enzyme
ATP and Cellular Work
Main types of (cellular) work:
mechanical
transport
chemical
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The Structure of ATP
– ATP (adenosine triphosphate)
• Consists of adenosine plus a tail of three phosphate
groups
• Is broken down to ADP and a phosphate group,
releasing energy
Energy
Triphosphate
Adenosine
P
P
Diphosphate
Adenosine
P
ATP
P
P
P
Phosphate
(transferred to
another molecule)
ADP
The Structure of ATP
ATP and Cellular Work
Motor protein
ATP
ADP
P
ADP
P
ADP
P
Protein moved
(a) Motor protein performing mechanical work
Transport
protein
Solute
P
P
ATP
Solute transported
(b) Transport protein performing transport work
P
ATP
X
P
Y
X
Y
ADP
P
Reactants
Product made
(c) Chemical reactants performing chemical work
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ATP and Cellular Work
ATP and Cellular Work
Redox reaction (oxidation-reduction)
oxidation
Xe- + Y
oxidation
X + Ye-
reduction
Na + Cl
Na+ + Clreduction
NAD+ (another activated carrier)
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