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Primary
Secondary
Tertiary
Protein Structure
Quaternary
Energy
Outline
I. Introduction
A. Metabolism
B. Energy defined
II. Laws of Thermodynamics
III. Energy Transfer in Living Systems
A. Chemical Reactions
B. ATP
Metabolism
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All the chemical reactions that occur in the cell
Capacity to get and use energy to build, store,
break down, and eliminate substances
necessary for growth and reproduction
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Catabolism: reactions that break down large
molecules into smaller ones e.g. digestion
energy released
Anabolism: reactions that build larger molecules
from small ones e.g. protein built from AA subunits
energy required
Energy
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Definition: the ability to do work, cause
change
Energy obtained from some cellular reactions is
used for fueling other reactions
Thermodynamics: The study of energy
Laws of Thermodynamics

1st Law: Energy in the universe is constant
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Energy can be transferred or transformed but it
cannot be created or destroyed
Also known as the Energy Conservation law
True for a closed system
Heat and Entropy
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Heat is energy and can do work (steam engine)
Conversion of any form or energy into heat is
not fully reversible, not all heat is usable energy
Heat “lost”=energy no longer capable of doing
work
Heat is “low quality” energy
Unusable heat associated with disorder
(entropy)
Energy flows from high quality to low quality
Laws of Thermodynamics

1st Law: Energy in the universe is constant
–
–
–

Energy can be transferred or transformed but it cannot be
created or destroyed
Also known as the Energy Conservation law
True for a closed system
2nd Law: Disorder in the universe is increasing
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–
Entropy: measure of disorder
In a closed system entropy increases
Maintaining Order
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Systems tend toward disorder
How do you explain order of a cell, or an
organism?
Input of energy required to maintain order
Energy Transfer in Living Systems
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
Each chemical reaction in a cell has reactants
and products
2 types of chemical reactions:
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–
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Exergonic: energy released meaning reactants
have more energy than products. Occur
spontaneously
Endergonic: energy required meaning reactants
have less energy than products
Sometimes these reactions are coupled
Energy Transfer in Living Systems
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Metabolic Pathway: series of chemical reactions
–
Often have reactants which are complexed into one or more
intermediates before final products
A+B→C→D→E+F
Where A, B are reactants C, D are intermediates E,F products
Specific enzymes required at each step (each arrow)

Chemical equilibrium: recall this occurs when forward
and backward reactions occur at the same rate.
Concentrations of reactants and products are stable but
not necessarily equal
Metabolic Pathway with inhibition (subtraction symbols)
ATP
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Adenosine triphosphate
Nucleotide based molecule- ribose, adenine,
and 3 phosphate groups
Cellular energy, powers cellular work
Bonds between phosphate groups can be
broken by hydrolysis
ATP + H2O ↔ ADP + Pi (inorganic phosphate) + energy

Phosphate groups all negative-repulse each
other, like a coiled spring
ATP molecule
ATP hydrolysis