Proteins Amino acids and peptides Lec Dr Muthana

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Proteins Amino acids and peptides, Lec. Dr. Muthana A. Al-Shemeri

Proteins Amino acids and peptides, Lec. Dr. Muthana A. Al-Shemeri

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myoglobin pdb code: 1 WLA Bacteriorhodopsin pdb code: 1 AP 9 Anti-parallel -sheets Parallel

myoglobin pdb code: 1 WLA Bacteriorhodopsin pdb code: 1 AP 9 Anti-parallel -sheets Parallel -sheets of lectin carbonic anhydrase pdb code: 2 LAL 3 pdb code: 1 QRM

Properties of Amino Acids • Capacity to polymerize • Novel acid-base properties • Varied

Properties of Amino Acids • Capacity to polymerize • Novel acid-base properties • Varied structure and chemical functionality • Chirality

 • The name protein is giving to compounds containing more than 100 amino

• The name protein is giving to compounds containing more than 100 amino acids. An amino acid part in a polypeptide or protein is called residue. • D-amino acids are not found in proteins but found in nature. • Crystalline amino acids are colorless, odorless, and melt with decomposition at temperature more than 200 °C. • The physical properties of amino acids are resemble those of inorganic salt such as sodium chloride

Functions of proteins 1. Enzymes : biological catalysis that are vital to all living

Functions of proteins 1. Enzymes : biological catalysis that are vital to all living systems. They are simple or conjugated proteins. 2. Structural proteins: proteins that hold living systems together such as collagen. 3. Hormones: proteins that act as messengers such as insulin. 4. Transport proteins: proteins that carry molecules and ions from one place to another in the living system such as hemoglobin carry oxygen from lung to cells. 5. Protective proteins: proteins that destroy any foreign substance released into the living system by an infections agent. 6. Toxin: proteins that are poisons such as snake venom.

Basic Amino Acid Structure carboxyl group § a-carbon is chiral (except for glycine) amino

Basic Amino Acid Structure carboxyl group § a-carbon is chiral (except for glycine) amino group § at p. H 7. 0 uncharged amino acids zwitterion. § amino acids have a tetrahedral structure a-carbon side chain

 • Proteins are make about two third of dry weight of cell •

• Proteins are make about two third of dry weight of cell • Major compounds of muscle, skin, and bones • The molecular weight varied from several thousand to several millions • Treated with a boiled acids or bases solution hydrolyzed the smaller compounds. • Twenty amino acids are obtain from hydrolysis of all living systems.

Amino Acid Enantiomers • Steroisomers / enantiomers • Biological system only synthesize and use

Amino Acid Enantiomers • Steroisomers / enantiomers • Biological system only synthesize and use L-aminoacids

Amino Acid Classification • • • Aliphatic Aromatic Sulfur containing Polar/uncharged basic/acidic Hydrophobic Hydrophillic

Amino Acid Classification • • • Aliphatic Aromatic Sulfur containing Polar/uncharged basic/acidic Hydrophobic Hydrophillic

Peptide bond formation

Peptide bond formation

Reaction of amino acids • The thiol side chain is oxidized by the oxygen

Reaction of amino acids • The thiol side chain is oxidized by the oxygen in air or oxidizing agent to form two cysteine molecules.