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Page 1: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Amino Acids & Peptides

Page 2: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

BIOMEDICAL IMPORTANCE

• the monomer units– L-α-amino

• Cellular functions– Nerve transmission– Biosynthesis of porphyrins– Purines– Pyrimidines – Urea

Page 3: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Biomedical Importance

• Peptides – Neuroendocrine system• as hormones,• hormone-releasing factors, • Neuromodulators,or neurotransmitters

Page 4: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

• One- & three-letter • Additional amino acids arise by modification– methylation, formylation, acetylation, prenylation,

and phosphorylation

Page 5: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

L- α-Amino acids present in proteins.

Page 6: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.
Page 7: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.
Page 8: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.
Page 9: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.
Page 10: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

• Amino Acids May Have Positive, Negative,• or Zero Net Charge

Page 11: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

• Zwitterions – equal number of ionizable groups of opposite

charge

• pKa – Express the Strengths of Weak Acids

Page 12: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Protonic equilibria of aspartic acid.

Page 13: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

• The net charge on an amino acid – Depends upon the pKa values of its functional

groups– the pH of the surrounding medium

• At Its Isoelectric pH (pI), an amino acid bears no net charge

Page 14: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

For lysine, pI is calculated from:

the pI for aspartic acid

Page 15: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Typical range of pKa values forionizable groups in proteins.

Page 16: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Amino Acid Sequence DeterminesPrimary Structure

Page 17: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Peptide Structures

Page 18: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.
Page 19: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

• Some Peptides Contain Unusual Amino Acids

Page 20: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

Glutathione (γ-glutamyl-cysteinylglycine).Note the non-α peptide bond that linksGlu to Cys.

Page 21: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

• Peptides Are Polyelectrolytes

• The Peptide Bond Has Partial Double-Bond Character

Page 22: Amino Acids & Peptides. BIOMEDICAL IMPORTANCE the monomer units – L-α-amino Cellular functions – Nerve transmission – Biosynthesis of porphyrins – Purines.

The four atoms of the peptide bond (colored blue) are coplanar