Structures of Proteins and
Denaturation
Presented to you by:Dylan Kutz,
Jacob Hare, and CJ Tyler
Primary Structure of Protein
• Consists of a sequence of amino acids in a
chain
• Each amino acid is comprised of a codon from
DNA
• A codon is made of three nitrogenous bases
from DNA
• The order of amino acids affects the
properties of the protein
Primary Structure of Proteins
• Examples:
• Human insulin is made of two amino acid
chains bonded by disulfide ridges
• It is necessary to utilize carbs
Secondary Structure of Protein
• Two Structures:
– a-helix
– B-pleated sheet
They repeat certain patterns of amino acids
Very few proteins have predominantly repeating
structures
A-Helix
• A single protein chain twists to form a helix
• Shape is maintained by hydrogen bonds
• All amino acids side chains extend outward
from the helix
B-pleated Sheets
• Occurs when amino acid chains run parallel to
each other
• Shape is also maintained by hydrogen bonds
Random Coil
• Only have certain portions of their structure in
helix or pleated sheet form
• Possible to have a-helix, b-pleated sheet, and
random coil structure at different points in a
molecule
Tertiary Structure of Protein
• 3 dimension arrangement of all atoms in a
molecule
• Unlike secondary structure it contains side
chains that are connected to the core
structure
• Stabilized in five ways
5 Ways to Stabilize
• Covalent bonds: Primarily disulfide ridges.
• Hydrogen bonds: They bond inter and intramolecularly. They will join the side chains and
the back bone of the molecule.
• Salt bridges: Occur when to ionized salt chains
come together to form salt bonds.
Stabilizing cont’d
• Hydrophobic interactions: In an aqueous
solution proteins group their polar groups
outward and their non polar groups inward
away from any water molecules. They interact
and form bonds that are weaker than
hydrogen bonds but act over a large surface
area.
Stabilizing cont’d
• Metal ion coordination: Two side chains that
have the same charge that would normally
repel each other are linked with a metal ion.
This is way the human body needs trace
metals because it is necessary to maintain
protein structures.
Quaternary Structure of Proteins
• The highest level of protein organization
• Have more than one polypeptide chain
• Determines how all the proteins come
together
Quaternary Continued
• Ex:
• Hemoglobin: four chains of amino acids.
Contains 2 alpha and 2 beta chains
• Collagen: Comprised of triple helix units called
tropocollagen. Stabilized by hydrogen
bonding between the 3 chains
Denaturation
• Any physical or chemical change to a structure
of a protein
• Ex:
• When cooking an egg with heat the proteins
in the egg denature to cook the egg
• Disulfide ridges in proteins can be broken by
2-mercaptoethanol; reduces them to SH
groups