Phys 02 14b
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Phys 02 14b Phys 02 14b Presentation Transcript

  • Objec&ve
2.14b
–
Enzymes
 •  Demonstrate
factors
 that
affect
enzyme
 ac&vity,
including
 denatura&on,
and
 interpret
graphs
 showing
the
effects
of
 various
factors
on
the
 rate
of
enzyme‐ catalyzed
reac&ons.


  • Enzymes
and
Specificity
 •  The
majority
of
the
genome
encodes
enzymes
 •  Each
enzyme
can
only
catalyze
a
specific
 reac&on
 –  Ac&ve
site
will
only
accommodate
a
par&cular
 substrate
(reactant)
 –  Helps
limit
the
“randomness”
reac&ons
 –  3‐dimensional
shape
coded
by
the
sequence
of
 amino
acids
(coded
by
DNA
sequence)
 •  Thousands
of
metabolic
reac&ons
within
an
 organism…thousands
of
unique
enzymes

  • Enzyme
Ac&vity
and

 Substrate
Concentra&on
 •  Enzyme
catalysis
lowers
 ac&va&on
energy
by
 elimina&ng
the
randomness
of
 reactant
collisions
 •  Arrival
of
the
substrate
 (reactant)
in
the
ac&ve
site
is
 s&ll
random
 •  Increase
probability
of
 substrate
entering
the
ac&ve
 site
by
increasing
substrate
 concentra&on
 –  Up
to
enzyme
satura&on

  • Enzyme
&
Protein
Shape
 •  Enzyme
ac&vity
is
dependent
on
the
availability
of
the
ac&ve
 site
 •  Protein
is
folded
into
a
specific
shape
as
it
is
synthesized
 •  Protein
primary
structure
held
together
by
nonpolar
covalent
 bond
(pep&de
bond…very
strong)
 •  Secondary,
ter&ary
and
quaternary
structure
held
together
by
 weaker
hydrogen
bonds,
hydrophobic
interac&ons
and
ionic
 bonds


  • High
Temperature,

 protein
denatura&on
 •  Atoms
and
molecules
are
constantly
in
mo&on.
 •  The
higher
the
temperature,
the
more
the
 movement
or
vibra&on
 •  The
more
movement/vibra&on,
the
less
stable
 the
chemical
bonds
that
hold
together
the
 molecule
 •  High
temperature
can
break
bonds
–
especially
 hydrogen
bonds
 •  The
enzyme
unfolds

  • Low
Temperature,

 less
reac&on
collision
 •  At
lower
temperatures,
 molecules
move
more
 slowly
 •  Less
vibra&on
=

more
 stable
bonds
within
the
 enzyme,
no
denatura&on
 But…
 •  Substrates
less
likely
to
 collide
 •  Reac&ons
less
likely
to
 occur

  • pH,
ions
and
Protein
Shape
 •  Secondary,
ter&ary
&
 quaternary
protein
structure
 can
be
disrupted
by
changes
in
 pH
 •  pH
is
a
measure
of
H+
 concentra&on
 •  H+
is
an
ion
that
can
compete
 for
binding
to
par&cles
with
 nega&ve
charges
and
thus
 break
bonds
 •  Each
protein
has
an
ideal
pH
 that
maintains
the
right
shape
 •  Same
effect
by
ions
or
salts