Download Proteins

Protein Structure
Review of Proteins
• Small molecules — 20 kinds
– 1 amino group
– 1 carboxyl group
– 1 "R" group
• Joined by peptide bonds to form
polypeptide
• Different sequence makes different protein
• Proteins are amino acid polymers
• Many roles in the cell…
– Enzymes
– Hormones
– Structure (muscle, hair, nails)
– Cell membrane pumps and channels
Amino Acid
Carboxylic Acid
Group
Amine
Group
R
“Alpha”
Carbon
The “R” Group
Placeholder
Levels of Protein Structure
• Like describing a knot by starting with the
strands of the rope
– Primary: The amino acid sequence
– Secondary: Coiling or folding
– Tertiary: folding, kinking, twisting entire structure
– Quaternary: Two or more chains together
Primary: The amino acid sequence.
– This is simply a list of the actual sequence of
amino acids in the "backbone" of the protein.
– You just start at one end and read off the
names of the amino acids in sequence and
you have described the primary sequence.
Secondary: Coiling of the chain.
– The "R" groups get in each other's way and
force a twisting of the chain into a coil.
Tertiary: Coiling of the coil.
– Like if you were to take a screen door spring
and tie it in a super knot
Quaternary: Two or more chains
together
– Not all proteins have this level.
– It only applies to proteins composed of two or
more separate polypeptides glued together.
– It refers to how the individual polypeptides are
attached.
Quaternary Structure
Illustration of Protein Structure
Primary
(Sequence)
Tertiary
(Bending)
Quaternary
(Layering)
Secondary
(Coiling)
Denaturation- When an unfavorable
change causes a protein to unravel and
lose its normal shape
1) A change in temperature
2) A change in pH
3) Some other environmental factor