Chapter 22 Notes 3 slides to a page - Scf

Proteins
Proteins
• The
most
important
of
all
biological
compounds
Chapter
22
• Derived
from
proteios
meaning
“of
first
importance”
FuncBons
of
Proteins
• Structure:

collagen
and
keraBn
• Catalysis:
enzymes
• Movement:
muscle
• Transport:
hemoglobin
• Hormones:
insulin,
human
growth
hormone,
etc
• ProtecBon:
anBbodies
• Storage:
casein
in
milk,
ovalbumin
in
eggs
• RegulaBon:
control
gene
expression
and
dictate
manufacturing
of
protein
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ClassificaBon
of
Protein
• Two
major
classes:
– Fibrous:
mainly
insoluble
in
water
– Globular:
more
or
less
soluble
in
water
Amino
Acids
• All
proteins
are
composed
of
small
subunits
called
amino
acids
• An
amino
acid
has
a
carboxyl
group
group
on
one
end
and
an
amino
group
on
the
other
• There
are
20
common
naturally
occur
amino
acid
Amino
Acids
Amino
acids
can
be
broken
into
4
classificaBon:
Non‐polar
Polar,
uncharged
Acidic
Basic
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Amino
Acids
Amino
acids
can
be
broken
into
4
classificaBon:
Non‐polar
Polar,
uncharged
Acidic
Basic
ZwiWerions
• Amino
acid
have
an
acid
and
a
base
end
• The
acid
and
base
cannot
co‐
exist
in
water
• So
the
acid
end
donate
a
proton
to
the
base
end
to
form
a
zwiWerion
Some
Uncommon
Amino
Acids
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Amino
Acids
Forming
Proteins
• A
carboxylic
acid
can
react
with
an
amine
to
form
a

amide
bond
• A
amide
bond
is
what
is
formed
between
amino
acids
• A
amide
bond
in
protein
is
called
a
pepBde
bond
or
pepBde
linkage
• If
two
amino
acid
join
you
get
a
dipeBde
Aspartame
• This
is
the
dipepBde
of
a
asparBc
acid
and
phenylalanine
• This
dipepBde
is
about
200
Bmes
sweeter
than
sugar
ProperBes
of
Proteins
• ProperBes
are
based
on
the
pepBde
backbone
and
the
side
chains
• The
pepBde
bond
is
almost
planar
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AGE
and
Aging
Protein
Structure:
Primary
• The
primary
structure
is
the
sequence
of
the
amino
acids
that
make
up
the
chain
• Many
different
possibility
– DipepBdes:
20
x
20
=
400
possible
– TripepBdes:
20
x
20
x
20
=
8000
possible
– 20n
where
n
is
the
length
of
the
protein
– If
a
small
protein
had
only
100
amino
acid
then
20 100 
=

1.27
x
10 130
The
Use
of
Human
Insulin
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Sickle
Cell
Anemia
Protein
Structure:
Secondary
• Protein
fold
to
align
themselves
in
such
a
manner
that
certain
paWerns
repeat
• The
repeaBng
paWerns
are
called
the
secondary
structure
• There
are
two
main
secondary
structures
• These
secondary
structure
are
mainly
held
in
place
by
hydrogen
bonding
Protein
Structure:
Secondary
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Protein
Structure:
TerBary
• The
terBary
structure
of
a
protein
is
the
three
dimensional
arrangement
of
every
atom
in
the
molecule
• The
terBary
structure
is
produce
and
stablized
by
pepBde
backbone
interacBon
and
side
chain
interacBon
Five
Stabilizing
Factors
• Covalent
bonding:
Disulfide
linkage
between
cysteine
residues
• Hydrogen
Bonding:
from
a
N‐H
or

O‐H
• Salt
Bridges:
between
a
acid
and
a
base
side
chain
• Hydrophobic
InteracBon:
water
pushed
non‐
polar
area
together
• Metal
Ion
CoordinaBon:
two
negaBve
side
chains
link
together
by
aWracBon
to
a
+
ion
Noncovalent
InteracBon
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Example
of
Stabilizing
Forces
Protein
Structure:
Quaternary
• The
highest
level
of
protein
structure
• It
is
not
found
in
all
protein
• It
involves
the
linking
of
subunits
• Very
large
proteins
Example
of
Quaternary
Proteins
• Hemoglobin
– Made
up
of
4
subunits
– Two
idenBcal
alpha
chains
and
two
idenBcal
beta
chains
– Each
globin
chain
surrounds
an
iron
containing
heme
unit
– The
non‐amino
acid
porBon
of
the
protein
is
called
a
prostheBc
group
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Example
of
Quaternary
Proteins
• Collagen
– A
triple
helix
units
called
tropocollagen
consBtute
the
soluble
form
of
collagen
– Collagen
consists
of
many
troprocollagen
units
– Troprocollagen
is
found
in
fetal
Bssue
and
young
connecBve
Bssue
– With
aging,
the
triple
helixes
crosslink
and
form
insoluble
collagen
Example
of
Quaternary
Proteins
• Integral
Membrane
Protein
– These
proteins
traverse
partly
or
completely
a
membrane
bilayer
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