Download Let`s Get Pumped Up about Proteins!!!

• “DNA is the flash; Proteins are the cash”
• 50-75% of biotechnology staff are concentrated on
protein research/manufacturing
• Typical cell produces ~2000 different proteins
• 9 different categories depending on function
(Table 2.1 pg. 57)
Functions of Proteins
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If you were to dry a cell,
75% of the remaining
mass would be
proteins!
structural support
signaling
movement
transport
response
defense
catalysis of reactions (enzymes)
• Biochemical compounds that contain nitrogen as
well as C, H, O, and sometimes S. (Remember:
CHNOS)
• consist of 1 or more polypeptide chains folded
and coiled into specific conformations
• What is the difference between a polypeptide
and a protein?
Polypeptide = polymer of amino acids
arranged in specific linear sequence
– linked by peptide bonds
– range in length from a few to 1000+
Protein = polypeptide folded into its 3-D stucture. Now
it is fully functional!
What?????
AMINO ACIDS
• Monomers of proteins
• cells use 20 amino acids to make proteins
• structure of an amino acid
– central carbon
– hydrogen atom
– carboxyl group
– amino group
– variable R group (side chain)
R-groups
The structure of
the R-groups
determines the
function of the
amino acid!
The folding of
the polypeptide
into a protein is
determined by
the interactions
between these
R-groups of the
amino acids.
• Amino acids are linked together by PEPTIDE
BONDS (links the carboxyl group of 1 amino
acid to the amino group of another)
**Remember: dehydration synthesis
is used to make the peptide bonds
PROTEIN STRUCTURE
A protein’s function depends on its specific
conformation (3-D shape)
There are four levels of protein structure:
1. Primary structure (linear sequence)
2. Secondary structure
3. Tertiary structure
4. Quaternary structure (largest structure)
• Now lets put together a protein!
1. Primary structure:
• unique, linear sequence of
amino acids (forms the
“backbone” of a protein)
– determined by genes
– slight change can affect a
protein’s conformation and
function (ex: sickle-cell
hemoglobin)
– can be sequenced in the
laboratory (insulin-Sanger)
2. Secondary structure
• regular, repeated coiling and folding of a
protein’s polypeptide backbone
• stabilized by H-bonds between peptide
linkages in protein’s backbone NOT the
R groups!
2. Secondary structure
• ALPHA HELIX = helical coil stabilized by Hbonding
• BETA PLEATED SHEET = sheet of antiparallel
chains folded into
“accordion” pleats
2. Secondary structure
3. Tertiary Structure
• Superimposed on 2° structure
• irregular contortions of protein
due to bonding between side
chains (R groups) resulting in
3-D shape
4. Quaternary Structure
• Some proteins consist of 2 or more
polypeptide chains
• association of several protein subunits to
form a single functioning molecule (ex:
hemoglobin or collagen)
collagen
Protein Conformation
• determined by physical and chemical
environmental conditions
• DENATURATION: process that alters a
protein’s native conformation and hence its
biological activity
– Temperature (ex: heat)
– chemical agents that disrupt H-bonding (ex: salt)
– transfer to an organic solvent (ex: ethanol)
– pH changes
SDS is a
detergent that
denatures
proteins!