Introduction to Metabolism
Metabolism
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Living organisms are full of chemical reactions
Produce and supply energy for cellular work
Energy is capacity to do work
Two states of energy
– Kinetic
– Potential
States of Energy
• Ability to do work
• Kinetic energy
– Energy of motion
• Potential energy
– Stored energy
– Dependent on location and structure
– Chemical potential energy
– Gravitation potential energy
• Forms of Energy
First Law of Thermodynamics
• Total amount of energy in any closed system is
constant. Energy cannot be created or
destroyed; it can only be converted from one
form to another. If a physical system gains an
amount of energy, another physical system
must experience a loss of energy of the same
amount.
Energy from Chemical Bonds
Chemical Reactions
• Energy changes in chemical reactions
• Chemical reactions involve breaking and
forming of new bonds
Bond Energy
• Measure of strength or stability of a covalent
bond
• Amount of energy absorbed/released per
mole when the bond is broken
Stages of a Chemical Reaction
Second Law of Thermodynamics
• In every energy transfer or conversion, some
of the useful energy in the system becomes
unusable and increases the entropy of the
universe
Spontaneous vs. Non-Spontaneous
• Spontaneous
– Ability for a reaction/change to continually occur
on its own once underway
• Non-spontaneous
– Reaction requires continual input of energy
• Dependent on 3 factors
– Temperature
– Energy changes
– Entropy
Favorable or Unfavorable?
Gibbs Free Energy
• Energy not lost in a reaction that can do useful
work
• Change in free energy:
– ΔG = Gfinal state – Ginitial state
• Not 100% accurate because some lost to
thermal energy
Exergonic vs. Endergonic
When I Move, You Move
• Energy coupling
– Exergonic and endergonic reactions are coupled
• Catabolic pathway
– Overall negative ΔG
• Anabolic pathway
– Overall positive ΔG
Homework
• Page 140 # 1,2, 4-10