Download 14.5 Uncommon Amino Acids

14.5 Uncommon Amino Acids
Uncommon amino acids
• Some but not all occur in protein
• Come form common amino acids that are
synthesized by the organism; process called
post-translation modification
• Hydroxyproline and hydroxylysine differ form
their parent amino acid because an –OH
group
Cont.
• Thyroxine is different from tyrosine because it
has an extra iodine
• “is found only in the Thyroid Gland”
• Thyroxine is a hormone that is released by
proteolysis
• Some common, uncommon amino acids are:
Proline, hydroxyproline, Lysine, hydroxylysine,
Tyrosine, Thyroxine
14.6 Amino acids combining to form
Proteins
14.6
• Two amino acids are joined together by a
peptide bond. (also called a peptide linkage)
• Any two amino acids can be linked together.
(this forms dipeptides)
• A third amino acid would be called a
tripeptide.
• Proteins are an important part of a living
organism
14.6
• Short chains are called peptides
• Longer chains are called polypeptides
• Amino acids in a chain are called residues.
14.7 What are the Properties of
Proteins?
• A continuing pattern of peptide bonds forms
the backbone of the protein
• The R groups are called the side chains
• Acid-base behavior is one of the most
important behaviors of the 20 different side
chains
• They behave as Zwitterions
14.7 charges of Proteins
• Isoelectric point of a protein occurs at the pH
where there's a balance in positive and
negative charges
• any pH above the isoelectric point is negative
• Any below is positive
• Some proteins like hemoglobin have an equal
charge
14.7 Solubility
• The solubility of proteins depends on the
repulsive forces in the surface
• When there is no repulsive forces the
molecules clump up and the solubility is
reduced
• They are least soluble at there isoelectric
points
14.8 What is the Primary structure of
Proteins?
14.8 structures of proteins
• Amino acids are the primary structures that
make up a chain of protein
• Different sequences of peptide and protein
molecules allows for the protein to carry out
its functions
• The formula for calculating the possible
numbers of peptides and proteins for a chain
of n amino acids by raising it to the 20th power
• 20ⁿ
14.8 cont.
• Peptides and proteins have their own unique
sequence of amino acids in the body
• Human insulin has two chains with a total of
51 amino acids.
• The two chains are connected by disulfide
bonds.
• People with diabetes have to take insulin
shots.
• Insulin used is from cattle and sheep.
14.8 cont.
• One change in the amino acid sequence can
cause sickle cell anemia.
• This shows how important the sequence of
the amino acid sequence is.