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.
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This is the process in which protein is synthesized.
Hydroxyproline & Hydroxylysine differ from their parent amino acids
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Their found in connective tissue proteins collagen
They have hydroxyl groups on their side chains.
14.5 Uncommon Amino Acids
Continued
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Thyroxine differs from tyrosine.
Has extra iodine-containing aromatic group on the side chain.
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Found only in the thyroid gland.
Formed by post-translational modification of tyrosine.
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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 –NH
3 group of a second molecule.
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─ this reaction takes place in the cell.
Produces an Amide.
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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
Two amino acids combined together.
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
─ 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.
The amino acid at the end of a peptide that has a free carboxyl group.
N-terminal amino acid is the residue with the free NH
3 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
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 CO
2
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
