Structure of an amino
acid (diagram).
What does this diagram
show?
The amine group,
contains an individual
nitrogen bonded to two
separate hydrogens.
What part of the amino
acid is highlighted?
What part of the amino
acid is highlighted?
The carboxyl group,
contains a carbon,
double bonded to an
oxygen atom and a
single bond to a hydroxyl
(OH-) group.
Why does the R group
effect the amino acid?
1
2
What type of bond
occurs between two
amino acids?
1
The R group can contain
carbon, hydrogen and
oxygen (and other
elements) in different
bonding patterns to form
different amino acids.
2
What type of reaction
occurs when two amino
acids form a peptide
bond?
Peptide bond, formed
between the available
carbon and nitrogen.
Condensation reaction.
The hydroxyl group within
the carboxyl group and
a hydrogen from the
adjacent amine group
bind to form H2O.
?
What test is used for
identifying proteins?
What results are
expected?
What process can speed
up the development of
positive results in a biuret
test?
When several amino
acids join, what form
of a protein is
produced?
Biuret test. A positive
result for proteins turns
the solution purple. A
negative test keeps the
solution blue.
Heating the solution in a
water bath.
Polypeptide.
When two amino
acids join, what form
of a protein is
produced?
Dipeptide.
What structure does
the sequence of
amino acids in a
polypeptide
produce?
Primary structure.
What structures are
found at the ends of
the primary structure
of a polypeptide
chain?
Amine group (NH2) and
carboxyl group (COOH).
Lysine, Valine,
Alanine and
Ascorbic acid are all
types of these.
What is the shape
the polypeptide
chain is twisted and
folded into as the
secondary
structure?
What characteristic
gives the tertiary
structure the shape
that is closely related
to its function?
Amino acids.
α-helix.
(Another form is the betapleated sheet, a flattened
chain).
Complex, 3D folded
structure.
Which type of bond
forms between R
groups, are
common, but are
not strong?
Hydrogen bonds.
Which type of bond
forms between an
amino acid which is
positively charged
and another which is
negatively
charged?
Ionic bond. This is if they
are close enough to
each other. These bonds
are not strong and easily
broken.
Which type of bond
forms between
amino acids that
contain sulfur in the
R-groups?
Disulfide bridge. Quite
strong covalent bonds.
These proteins are
typically
long and

thin, as well as
insoluble used for
structure and
support.
Fibrous proteins.
Examples of fibrous
proteins include:
collagen (tendons –
connective tissue), actin
and myosin (used for
muscle movement) and
keratin (hair).
These proteins are
more spherical in
shape with
metabolic /
biochemical
functions.
Globular proteins.
Examples of globular
proteins include: enzymes
and myoglobin (stores
oxygen in muscle tissue).
Proteins that involve
more than one
peptide chain form
which type of
structure?
Quaternary structure. An
example of this is
haemoglobin; having
four polypeptide chains
with associated haem
groups.
What name is given
to the associated
groups which are
not made from
amino acids in a
peptide?
Prosthetic group. Haem
within haemoglobin is an
example of this.
Which two
compounds are
used in the Biuret
test?
Sodium hydroxide
(added first) then dilute
copper sulfate (in equal
amounts).
Describe what
protease is and
what it is made
from?
An enzyme that breaks
down proteins, that is
made of different amino
acids.