Download Chapter 8 PPT

Chapter 6
An Introduction to Metabolism
Metabolism, Energy, and Life
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Metabolism – totality of an organism’s
chemical processes
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Catabolic Pathways – release energy by
breaking down complex molecules into simpler
ones
Anabolic Pathways – consume energy to build
complex molecules into simpler ones
Energy – capacity to do work
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Kinetic Energy – energy in motion (heat/light)
Potential Energy – energy of position
(chemical energy stored in bonds)
Laws of Thermodynamics
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First Law of Thermodynamics –
energy can be transferred or
transformed but neither created nor
destroyed
Second Law of Thermodynamics –
every transfer of energy increases
disorder (entropy)
Types of Reactions
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Exergonic Reaction – products that
contain less energy than the reactants,
therefore, energy is lost; heat is given
off contributing to disorder
Endergonic Reaction – products store
more energy than the reactants,
therefore, absorbing and storing energy
ATP (Adenosine Triphosphate)
ATP powers cellular work
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Functions:
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Mechanical work such as beating of cilia
Transport work such as pumping substances
against concentration gradients
Chemical work such as Endergonic process of
polymerization
Structure of ATP
Adenosine Triphosphate – nucleotide
with unstable phosphate bonds that the
cell hydrolyzes for energy to power
endergonic reactions

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Hydrolysis of ATP
Hydrolysis of ATP – the terminal phosphate
bond is hydrolyzed, a phosphate group is
removed producing ADP (exergonic)
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Terminal phosphate bond is highly unstable; ADP is
the stable form of the molecule
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ATP + H2O  ADP + P
Regeneration of ATP (endergonic)
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Energy is stored in the phosphate bonds
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ADP + P  ATP
Enzymes
Enzymes – speed up metabolic reactions by
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lowering energy barriers
Catalyst – chemical agent that accelerate reactions without
being changed or used up; able to be used over and over
again (enzyme)
Activation energy – energy needed by reactants to start a
reaction (enzymes lower)
Substrate Specific – One enzyme for one substrate
(molecule/compound being broken down)
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Substrate binds to the active site of the enzyme changing the
shape of the enzyme (induced fit)
Enzymatic cycle
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Substrate binds to the active site of the enzyme forming an
enzyme substrate complex
Induced fit of the active site around the substrate
Product departs active site and the enzyme emerges in its
original form
Effects of Enzyme Activity
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Denaturation – The breakdown of the quarternary
and tertiary structures of the protein that will render
the protein inactive
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Temperature and pH
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Cofactors – small nonprotein molecules required for
proper enzyme catalysis
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Temp – increasing temp. increases reaction rates due to
more kinetic energy between substrates and active sites
colliding (denaturation occurs after 400C in humans)
pH – optimum is between 6-8 in humans
Inorganic – zinc, iron, copper
(Coenzymes) organic – vitamins
Inhibitors
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Competitive Inhibitor – chemicals that resemble an
enzymes substrate and compete with it for the active site
Noncompetitive Inhibitors – chemicals that do not bind to
the active site but bind another part of the enzyme
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Change shape of the active site so that substrate can not
bind to it
Control of Metabolism
Allosteric Regulation
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Allosteric Site – specific receptor site on some
part of the enzyme molecule other that the active
site
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Activator – stabilizes the active form of enzyme
Inhibitor – stabilizes the inactive form of enzyme
(noncompetitive)
Feedback Inhibition – regulation of a
metabolic pathway by its end product, which
inhibits an enzyme within the pathway