Part 4: Ch 5STRUCTURE & FUNCTION OF PROTEINS
9/06/2016
AP Bio Vocabulary of the Day
(Stems, Prefixes, and Suffixes…Oh my!)
bath- depth
Example: bathysphere (a deep-sea
submersible lowered on a cable)
Fabulous Fact
The African Elephant gestates for 22
months. The short-nosed Bandicoot has
a gestation period of only 12 days.
You Must Know…
To understand the structure and function of
proteins.
AP Biology Standards addressed: Big Idea 2
People to Ponder
Frederick Sanger
Sanger was born in 1918 in Rendcombe, England.
Sanger’s father was a doctor and wanted his son to follow in his footsteps.
Sanger enrolled at Cambridge and became interested in nature and science. He decided to
study this because a career in science gave him a better chance of being a problem solver.
His decision was probably made harder and easier when both of his parents dies of cancer his
first two years at Cambridge.
When WWII broke out in Europe Sanger registered as a conscientious objector due to his
Quaker upbringing.
Sanger joined the Cambridge Scientists Anti-War Group and there met his future wife Joan
Howe who was also studying at Cambridge.
Sanger and Joan married after he graduated in 1940. They went on to have three children:
Robin (1943), Peter (1946), and Sally Joan (1960).
Frederick Sanger
Sanger went on to get his Ph.D. at Cambridge studying amino acid metabolism. He continued
his studies afterwards and worked on identifying free amino groups in insulin.
Through his research Sanger figured out how to order amino acids and became the first person
to sequence a protein.
Sanger’s work proved that proteins were ordered molecules and therefore genes and DNA also
had to have an order and sequence.
Sanger was awarded the Nobel Prize for Chemistry in 1958 for determining the structure of a
protein.
In 1951 he began working for the Medical Research Council at Cambridge. In 1962 they
moved to join the Lab for Molecular Biology where Francis Crick and others worked on DNA-
related problems.
Sanger started to work with RNA because it was smaller and developed the dideoxy method
that was transferable to DNA and is the most common method for sequencing reactions today.
Sanger won a second Nobel Prize for Chemistry (shared with Walter Gilbert and Paul Berg) in
1980 for contributions to determining the base sequence of nucleic acids.
Frederick Sanger
Sanger is the 4th person to win two Nobel Prizes and one of only two people to win twice in the
same category (the other is John Barden in Physics).
He retired in 1985 and spent most of his time working in the garden.
Sanger credited his wife for being the supportive presence that made his work and life possible.
He turned down knighthood because he didn’t want to be addressed as “Sir” and be seen as
different and set apart.
In 1992 the Welcome Trust and Medical Research Council established the Sanger Centre. It’s
focused on furthering knowledge of genomes and was key in the Human Genome Sequencing
Project.
Sanger died in his sleep in November 2013.
He described himself as “just a chap who messed about in the lab…academically not brilliant.”
Sanger is remembered as “a true ‘gentle’ man, extremely courteous and charming.”
(www.dnaftb.org)
I. Proteins
• “Proteios” = first or primary
• 50% dry weight of cells
• Contains: C, H, O, N, S
Myoglobin protein
Protein Functions (+ examples)
• Enzymes (lactase)
• Defense (antibodies)
• Storage (milk protein = casein)
• Transport (hemoglobin)
• Hormones (insulin)
• Receptors
• Movement (motor proteins)
• Structure (keratin)
Overview of protein functions
Overview of protein functions
Protein Structure and Folding
Proteins are constructed of amino acids bonded together.
Anatomy of an amino acid:
Amino group (NH2)
Carboxyl group (COOH)
R group (side group- unique to each type of amino
acid)
Carbon in the center bonded to all groups and one H
Structure has been studied in depth using X-ray
crystallography
Phenylalanine
Primary Structure- a chain of amino acids bonded together via dehydration synthesis
(polypeptide chain)
The bonds between amino acids are called peptide
bonds
The sequence of the amino acids determines the
shape and type of protein.
Secondary Structure- coiling and folding of the chain of amino acids – gains 3-D shape. The
result of H-bonds.
Alpha (α) helix: coiled chain
Beta (β) pleated sheet: folded sheets
Basic Principles of Protein Folding
A. Hydrophobic AA buried in interior of protein
(hydrophobic interactions)
B. Hydrophilic AA exposed on surface of protein
(hydrogen bonds)
C.Acidic + Basic AA form salt bridges (ionic bonds).
D. Cysteines can form disulfide bonds. This creates
more stability in the protein shape.
Tertiary Structure- folded chain with the overall shape of the protein.
Involves the interaction of the R groups
Often reinforced with disulfide bridges
Can also involve H-bonds, ionic bonds, and
hydrophobic interactions
Quaternary Structure- 2 or more polypeptide chains and possibly nonpolypeptides collected
into one macromolecule.
example: hemoglobin
example: collagen fibers
amino acids polypeptides protein
Bonding (ionic & H) can create
asymmetrical attractions
The shape of a protein determines the function of a
protein and is INCREDIBLY important.
There is folding assistance to ensure correct shape.
Chaperonins- protein molecules that assist in the
folding of other proteins.
Proteins can lose their shape (denature) when
conditions change- change in pH, temperature, etc.
• Protein structure and function are sensitive to chemical and
physical conditions
• Unfolds or denatures if pH and temperature are not optimal
change in structure = change in
function
Modified from Anna VanDordrecht (SCOE)
& Mrs. Chou (Longmont High School)
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