Amino Acids Chemistry & Protein Chemistry PDF

Amino acids chemistry Protein chemistry Prof. Dr. Dina Sabry Dr. Dalia Badran Dr. Shimaa Mohsen Dr. Mai Abdelaziz Dr. Dina MEKAWY  LOs Identify general formula of amino acid Classify amino acids nutritionally Classify amino acids as hydrophobic or hydrophilic...

Amino acids chemistry Protein chemistry Prof. Dr. Dina Sabry Dr. Dalia Badran Dr. Shimaa Mohsen Dr. Mai Abdelaziz Dr. Dina MEKAWY  LOs Identify general formula of amino acid Classify amino acids nutritionally Classify amino acids as hydrophobic or hydrophilic Identify conversion of amino acids to specialized products. Enumerate Biological importance and function of proteins Describe the structure of proteins Explain properties of proteins Classify proteins AMINO ACIDS AMINO ACIDS Proteins are organic compounds with a high molecular weight. Twenty different amino acids are commonly required for synthesis of proteins, all are α-amino acids. Amino acids are organic acids (COOH), which have amino group (NH2). Amino acids are the building units of protein.  Chemical Classification of amino acids Neutral: monocarboxcylic and monoamino groups Acidic: Dicaboxcylic and monoamino groups Basic: Diamino and monocaboxcylic groups  Neutral amino acids Neutral: monocarboxcylic and monoamino groups Glycine Alanine  Neutral amino acids Neutral: monocarboxcylic and monoamino groups Hydroxyl Serine containing amino acids Therionine Sulphate Cysteine containing amino acids Methionine Methionine in the active form S-adenosyl methionine (SAM) is used as methyl donor. Trans-methylation reactions are catalyzed by different methyl transferases. methyl transferase - Nor-epinephrine Epinephrine (hormone metabolism) SAM  Acidic amino acids Acidic: Dicaboxcylic and monoamino groups Aspartic acid Glutamic acid  Basic amino acids Basic: Diamino and monocaboxcylic groups: Lysine, Arginine and Histidine Lysine Mid term short essay exam: Explain on biochemical basis The chemical structure of lysine is essential for DNA epigenetic regulation by histone modification  ANSWER Lysine amino acid is basic hydrophilic amino acid is essential for nucleosome structure (DNA packaging and epigenetic regulation by histone modification through Lysine acetylation and lysine methylation in ACTIVATION AND A) Model of a nucleosome composed of 8 histone proteins with exposed tails (darker grey INACTIVATION OF DNA which is rich in hydrophilic lysine a.a.) and REPLICRION). wrapped DNA (lighter grey). B) Structure of euchromatin (“beads on a string”). C) Structure of heterochromatin. Epigenetic regulations for activation and inactivation of DNA replication Histidine: Hydrophilic polar basic amino acid It is precursor for histamine, an amine produced by the body in inflammation and hypersensitivity allergic reactions by Histidine by decarboxylation reaction.  Nutritional Classification of Amino Acids I- Essential Amino Acids They are not formed in the body. It is essential to supply them in diet. Their deficiency decreases the rate of growth and protein synthesis. They are 9 in number: 1- Valine 2- Leucin 3-Isoleucine 4-Threonine 5- Methionine 6- Lysine 7- Phenylalanine 8- Tryptophan 9- Histidine II- Half-essential or Semi-essential Amino Acids They are formed in the body at a rate enough for adult but not for growing animals (Arginine ) III- Non-essential Amino Acids They are formed in the body mostly from carbohydrates at a rate enough for growing and adult animals. These include the rest of amino acids Proteins that contain all the essential amino acids are of high biological value, e.g. milk and egg proteins. Proteins that are deficient in one or more of the essential amino acids are of low biological value, e.g. collagen and elastin. Classification of amino acids as hydrophobic or hydrophilic ▪ Depending on the interaction of side chains with water. ▪ In general, proteins fold so that amino acids with hydrophobic side chains are in the interior of the molecule where they are protected from water, while those with hydrophilic side chains are on the surface in contact to water on the outside of the molecule. ❖Hydrophobic amino acids: 1. Phenylalanine and tyrosine. 2. Tryptophan. 3. Valine, leucine, and isoleucine. Hydrophilic amino acids Have side chains that contain O or N atoms; some of the hydrophilic side chains are charged at physiologic pH. The acidic amino acids (aspartic and glutamic acids) have carboxyl groups that are negatively charged, Whereas The basic amino acids (lysine, arginine, and histidine) have nitrogen atoms that are positively charged.  Location of nonpolar amino acids in soluble and membrane proteins Nitrogen Balance Nitrogen balance is the (normal) condition in which the amount of nitrogen incorporated into the body each day exactly equals the amount excreted. Negative nitrogen balance occurs when nitrogen loss exceeds incorporation. Positive nitrogen balance occurs when the amount of nitrogen incorporated exceeds the amount excreted.  Positive nitrogen balance Occurs when the amount of nitrogen incorporated exceeds the amount excreted. It is associated with: Growth Pregnancy Recovery phase (of injury or surgery or condition associated with negative nitrogen balance)  Negative nitrogen balance Negative nitrogen balance occurs when nitrogen loss exceeds incorporation. It is associated with: Protein malnutrition (kwashiorkor) Dietary deficiency of even 1 essential amino acid Starvation Uncontrolled diabetes Infection