Download Amino Acids 14.5 * 14.8

Amino Acids
14.5 – 14.8
By: Jean Turber, Kaitlin Clark
& Kurstyn Pfleegor
14.5 Uncommon Amino Acids




Occur in some proteins, but not all.
Derived from common amino acids.
Produced in a process called post-translational
modification.
‾ This is the process in which protein is
synthesized.
Hydroxyproline & Hydroxylysine differ from their
parent amino acids
‾ Their found in connective tissue proteins
‾
‾
collagen
They have hydroxyl groups on their side chains.
14.5 Uncommon Amino Acids
Continued

Thyroxine differs from tyrosine.
‾ Has extra iodine-containing aromatic
group on the side chain.
‾ Found only in the thyroid gland.
‾
Formed by post-translational modification of
tyrosine.
‾
‾
This process produces in the protein
thyroglobulin.
Released as a hormone by proteolysis of
thyroglobulin.
14.5 Structures
 Proline
Lysine
Tyrosine
Thyroxine
14.6 How do Amino Acids
Combine to Form Proteins?
 Amino
Acid has a carboxyl group and an
amino group.
 The –COO group of one amino acid
molecule can combine with the –NH3
group of a second molecule.
─
─
─
─
this reaction takes place in the cell.
Produces an Amide.
The two Amino Acids are joined together by an
peptide bond. (the linking of two amino acids)
Produces dipeptide.
14.6 Example Reaction
 Glycine
+
Alanine
=
Glycyalanine
14.6 Continued

Dipeptide
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

By adding more amino acids it will turn into a
tripeptide, tetrapeptide ect.
Chain of hundreds or thousands of amino acids
make up protein that serve many functions in living
organisms.
The order of chain length goes by peptide (shortest),
polypeptide, proteins (longest).
Polypeptides contain 30-50 amino acids
─

Two amino acids combined together.
the amino acids in the chain are called residues
One letter or three letter abbreviations are used to
represent proteins and peptides ( Ala, Gly, Lys)
14.6 Continued

C-terminal amino acid is the residue with
the free –COO group.


N-terminal amino acid is the residue with
the free NH3 group.


The amino acid at the end of a peptide
that has a free carboxyl group.
Has a free amino group.
Proteins are synthesized from N-terminal
to C- terminal.
14.7 What are the Properties of
Proteins?
The R group are called the side chains.
 The 6 atoms of the peptide backbone lie
on the same plane.



2 adjacent peptide bonds can rotate
relative to one another.
The side chains determine the physical
and chemical properties of proteins.
14.7 Properties




Proteins behave as zwitterions.
Side chains of glutamic and aspartic acids
provide acidic groups.
Lysine and Arginine provide basic groups.
The isoelectric point of a protein occurs at the pH
 equal number of positive and negative
charges.
 Any pH above the isoelectric point the
molecules have a negative charge.
 Any pH below the isoelectric point the
molecules have a positive charge.
14.7 Properties Continued

Hemoglobin has equal numbers of acidic
and basic groups.


has a pH of 6.8
Serum albumin has more acidic groups
than basic groups.

pH of 4.9
Proteins act as buffers in the blood.
 Water solubility depends on repulsive
forces between like charges.

14.7 Properties Continued


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

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Protein molecules have a charge that causes
them to repel one another.
When there are no repulsive forces protein
molecules clump together to form two or more
molecules, reducing there solubility.
Primary structure describes the linear sequence of
amino acids in the polypeptide chain.
Secondary structure refers to repeating patterns.
Tertiary structure describes the overall
conformation of the polypeptide chain.
Quarternary structure applies mainly to proteins
containing more than one poly peptide chain.
14.8 What is the Primary
Structure of Proteins?
 The
primary structure consists of a
sequence of amino acids in a chain
 Decarboxylation

Loss of CO2
 Each
protein has its own unique
sequence of amino
 Naming them starts at the N-terminal end
 The primary structure determines the
native secondary and tertiary structures
14.8 Protein Structures
14.8 Continued
 Particular
sequences of amino acids allow
the whole chain to fold up or curl up
 Different sequences may or may not
affect the way it functions

Cytochrome
 In
humans, chimpanzees, sheep, and other
animals
 Humans and chimpanzees have the same
sequence
14.8 Continued
 People
with diabetes use insulin from cows,
sheep, and hogs
 The difference in insulin is in the 8,9, and 10
positions of the A-chain and the C-terminal
position of the B-chain

Not as affective as human insulin
 Human

insulin is produced from bacteria
Some people can be allergic to bovine insulin
14.8 Hormones
 Two


peptide hormones
Oxytocin
Vasopressin
 Identical

structures
Disulfide bonds
 Difference

in the amino acids in positions 2 & 7
Vasopressin increases the amount of water
reabsorbed by the kidneys and raises blood
pressure
14.8 Hormones Continued
 Oxytocin
affects the contracts of the
uterus at child birth
 In the blood protein hemoglobin a
change in any one of the 146 amino
acids is enough to cause sickle cell
anemia
 The sequence of an amino acids very
important
 Sequence of 10,000 protein and peptide
molecules have been determined
14.8 Hormone Structures
 Oxytocin
Vasopressin