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The Central Dogma
The Central Dogma
POINT > Describe 4 roles proteins play in cells
POINT > Define the primary structure of protein
POINT > Describe the structure of amino acids
POINT > Describe and identify peptide bonds
POINT > Describe 4 roles proteins play in cells
1. Many proteins act as enzymes, catalyzing
reactions, and there are lots of them in the cell!
These include enzymes like the DNA and RNA
polymerases, DNA ligase, helicase, and 1000’s of
others
POINT > Describe 4 roles proteins play in cells
2. Proteins provide structural support and
define cell shape
Ex. cytoskeleton and spindle fibers
POINT > Describe 4 roles proteins play in cells
3. Proteins act as intra- and extra-cellular messengers
Ex. insulin regulates glucose entry into cells
oxytocin initiates uterine contractions during
childbirth
vasopressin causes kidneys to conserve water
during dehydration
POINT > Describe 4 roles proteins play in cells
4. Proteins are critical to body defense and
the immune system
Ex. antibodies identify foreign viruses and
bacteria and target them for destruction
WB CHECK:
Identify 4 jobs that proteins perform:
Which is not a role of proteins?
a) provide physical structure to cells
b) protect against viruses and bacteria
c) carry genetic information
d) act as cell messengers
e) speed up chemical reactions
POINT > Define the primary structure of protein
What do proteins look like?
POINT > Define the primary structure of protein
These globular proteins (some are much smaller)
are made up of one long string of amino acids
POINT > Define the primary structure of protein
To fulfill their roles, proteins must fold into a
VERY specific configuration
The primary structure of a protein is the amino
acid sequence
POINT > Describe the structure of amino acids
Amino acids are the building blocks of peptides and
proteins
Amino acids are small molecules that are linked
together by a type of covalent bond: the peptide bond
There are 20 amino acids from which all human
proteins are constructed
WB CHECK:
Proteins are made up of
a) chains of amino acids
b) carbohydrates
c) sequences of nucleotides
d) amino acids and nucleic acids
WB CHECK:
The primary structure of a protein is
a) the specific shape it folds into
b) the sequence of nucleotides that make the protein
c) dependent on the role of the protein
d) the sequence of amino acids that make the protein
WB CHECK:
What holds the amino acids in a protein
together?
Peptide bonds are a type of
a) hydrogen bond
b) complementary bonding
c) covalent bond
d) ionic bond
POINT > Describe the structure of amino acids
All amino acids have this basic structure:
R Group (different for each a.a.)
Amino group 
Central carbon
Carboxyl group
POINT > Describe the structure of amino acids
WB CHECK:
What are the 4 parts of an amino acid?
How many different amino acids are there in
human proteins?
Which part of an amino acid has a nitrogen (N)
atom?
Which part of an amino acid is different for
each amino acid?
POINT > Describe and identify peptide bonds
Amino acids are linked together by peptide bonds
Peptide bonds form between the amino group of
one amino acid and the carboxyl group of another
POINT > Describe and identify peptide bonds
POINT > Describe and identify peptide bonds
POINT > Describe and identify peptide bonds
As more amino acids are added the protein gets longer
Like DNA, proteins have polarity: always an amino
group on one end and a carboxyl group on the other
Amino group
Carboxyl group
POINT > Describe and identify peptide bonds
The R-groups of each amino acid can interact with
each other
R-group interactions control the way the protein folds
up
R groups
WB CHECK:
How many amino acids are in the protein shown here?
POINT > Define the primary structure of protein
As the protein is built, new amino acids are always
added to the carboxyl end of the chain
Interactions between R groups on neighboring and
distant amino acids govern the final shape of the
protein
WB CHECK:
If another amino acid was to be added to this chain,
would it be on the right or the left side?
Later we will see how an mRNA molecule is
used to create a protein (Translation)
Homework:
Workbook pages 57-60