Download Enzymes - SBI4UAssumption

Biochemistry Unit
Textbook: pg. 69
Workbook: pg. 61
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http://www.sumanasinc.com/webcontent/ani
mations/content/enzymes/enzymes.html
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Enzymes are biological catalysts that increase
the speed of biochemical reactions within cells.
Enzymes are globular proteins that are NOT
consumed during reactions. This means they are
readily available to catalyze the same reaction
over and over again.
Enzymes speed up chemical reactions by
lowering the activation energy needed for the
reaction to proceed. Without the presence of
enzymes, biochemical reactions within the cells
would not occur fast enough to sustain life.
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EXERGONIC
REACTION:
 products have a
lower energy than
the reactants
 products have less
free energy than
that of the
reactants and
energy is given off
from the system.
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ENDERGONIC
REACTION :
 Products have a higher
energy than the
reactants
 The system requires
energy
 These reactions cannot
occur spontaneously,
energy is required to
be invested in the
products.
The shape of an enzyme is so specific that only
one type of substrate (reactant) is capable of
properly binding to the enzyme. If the shape of the
enzyme should change or become altered, the
enzyme will be inactive and the chemical reaction will
not be catalyzed.
 Most enzymes end with “ase”. So if you are
struggling with the name of an enzyme and you know
the name of the substrate, just change the ending to
“ase”. So lactase is the enzyme involved with
converting lactose into glucose and galactose.
Amylose is the substrate for the enzyme amylase.
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
http://lgfl.skoool.co.uk/content/keystage3/bi
ology/pc/learningsteps/PAELC/launch.html
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Digital Experiment:
http://lgfl.skoool.co.uk/content/keystage3/bi
ology/pc/learningsteps/DIELC/launch.html
Textbook: pg. 72
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http://lgfl.skoool.co.uk/content/keystage3/bi
ology/pc/learningsteps/TAELC/launch.html
Textbook: pg. 72
http://www.lpscience.fatcow.com/jwanamaker/animations/Enzyme%20activity.html
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In an enzyme catalyzed reaction,
the substrate binds to a location
called the active site.
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A substrate-enzyme complex
forms when the substrate binds
to the enzyme.
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The active site involves a small
number of key residues that
actually bind to the substrates
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The rest of the protein
structure is needed to
maintain these residues in
position
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Initially the active site is
not a direct fit for the
substrate.
 As the substrate begins to
interact with the amino
acid side chains of the
enzyme, the enzyme
modifies its shape to
better accommodate the
substrate.

This slight change in the
shape of the enzyme
allows the enzyme to
catalyze the reaction.
Workbook : pg. 61
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Some enzymes require co-factors or co-enzymes to
help them function properly. Co-factors are inorganic,
non protein molecules that include zinc, iron, and
copper. These metal ions can either bind to the active
site or to the substrate to facilitate the formation of
the enzyme-substrate complex.
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Some of the most important coenzymes include
nicotinamide adenine dinucleotide (NAD+) and
nicotinamide adenine dinucleotide phosphate
(NADP+) which are involved in the process of cellular
respiration and photosynthesis, respectively. These
two molecules carry electrons during both reactions.
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There is an array of substances that can
inhibit and deactivate enzyme activity by:
either:
 altering the active site or by
 mimicking the structure of a particular substrate.
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There are two types of inhibition:
competitive and noncompetitive.
Textbook: pg. 73
Workbook : pg. 61
 Compete with the substrate for the enzyme's active site.
 Enter the enzyme's active site and prevent the normal
substrate from binding.
 Attaches to a binding site on an enzyme other than the
active site.
http://bcs.whfreeman.com/thelifewire/content/chp06/0602001.html
Textbook: pg. 74
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Cellular Respiration (text pg. 113) – negative feedback
Oxytosin and birth (text pg.336) – positive feedback
http://www.northland.cc.mn.us/biology/Biology1111/animations/enzyme.html
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Cells need to regulate and control chemical reactions
in order to coordinate cellular activities.
 control enzyme activity by:
▪ altering the production of a particular enzyme
▪ preventing an enzyme from functioning.
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Some enzymes contain allosteric sites which are
receptor sites that are located far from the active
site.
 Allosteric activator: keeps the active site of an enzyme
available to its substrate.
 Allosteric inhibitor: is a substance that binds to the allosteric
site and induces an inactive form of an enzyme so that the
substrate cannot bind.
Workbook : pg. 63
http://www.stolaf.edu/people/giannini/flashanimat/enzymes/allosteric.swf
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