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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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Enzymes
Induced Fit
Enzymes
Enzymes are catalytic proteins
Enzymes lower the barrier of EA
Activation Energy
– Activation energy
• Activates the reactants
• Triggers a chemical reaction
– Enzymes lower the activation energy for chemical
reactions.
Activation
energy barrier
Reactant
Energy level
Energy level
E
Enzyme
Reactant
Products
(a) Without enzyme
Activation
energy barrier
reduced by
enzyme
Products
(b) With enzyme
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Enzymes
Enzymes
Physical and chemical
properties affect enzyme
activity:
Substrate
Active site
*activators
*cofactor
coenzyme
*coenzyme
Inhibitor
Active site
Substrate
*inhibitors
Active site
Substrate
Inhibitor
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
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