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Transcript
UNIT 8 THE AMINO ACIDS LEARNING OBJECTIVES State the composition and describe the structure of amino acids. Classify amino acids. List essential, semi-essential and non- essential amino acids. 2 AMINO ACID Principal source: hydrolysis of protein Proteins: high molecular weight substances (found in all living tissues) attached to the same α-carbon 3 AMINO ACID STRUCTURE OH +H N 3 C R O R BUILDING AN R GROUP Glycine Alanine Phenylalanine Tyrosine H CH3 CH2 CH2 OH • With an H, glycine is the simplest amino acid • Alanine with a methyl group is the next simplest. • Phenylalanine arises when a phenyl group replaces an H on alanine’s methyl group • Tyrosine evolves by adding an –OH group to the para position on the phenyl ring of phenylalanine Substances (found in all living tissues) Upon Acid, base or enzymes catalyzed hydrolysis: Broken into thousands of amino acids molecules Most proteins produce approximately 20 different αamino acids Amino Acids - have both an amino & a carboxylic acid group attached to the same α-carbon 6 FUNCTIONS OF AMINO ACIDS 1. Building blocks of proteins 2. Specific amino acids give rise to specialized products: 7 FUNCTIONS OF AMINO ACIDS 2. Specific amino acids give rise to specialized products: • TYROSINE forms thyroid hormones T3 T4 and melanin • TRYPTOPHAN can synthesize a vitamin called niacin • GLYCINE, ARGININE AND METHIONINE synthesize creatinine. • GLYCINE and CYSTEINE helps in the synthesis of bile salts. • CYSTEINE and METHIONINE are sources of sulphur. 8 LEARNING OBJECTIVES State the composition and describe the structure of amino acids. Classify amino acids. List essential, semi-essential and non- essential amino acids. 9 Classification and Structure of Amino Acids Neutral Acidic Basic •Alipathic •Aromatic •Heterocyclic •Sulphur containing amino acids 10 LEARNING OBJECTIVES State the composition and describe the structure of amino acids. Classify amino acids. List essential, semi-essential and non-essential amino acids. 11 ESSENTIAL AMINO ACIDS 8 Amino Acids not Synthesized by the body & Therefore Must Be Taken in the Diet 1. Leucine 2. Isoleucine 3. Threonine 4. Tryptophan 5. Phenylalanine 6. Valine 7. Metheonine 8. Lysine Mnemonic Pvt. Tim Hall 563 427 18 H – Histidine A – Arginine 12 ESSENTIAL AMINO ACIDS Leucine Isoleucine Threonine Tryptophan Phenylalanine Valine Metheonine Lysine To Maintain The Proper Nitrogen Balance In The Body DEFICIENCY (1 or more) CHILD: Growth failure ADULT: decrease plasma protein and hemoglobin levels 13 SEMI-ESSENTIAL AMINO ACIDS Histidine Arginine Synthesized partially by the body But not at the rate to meet the requirement in growing children, pregnant and lactating women 14 NON-ESSENTIAL AMINO ACIDS Alanine Aspartic acid Serine Proline •Can be synthesized by the body •May not be required in the diet •Derived from carbon skeletons of lipids and carbohydrates during metabolism or from the transamination of essential amino acids 15 • Complete or Adequate Proteins: Animal Proteins- Supply all of the essential amino acids. • Incomplete Proteins: Vegetable Proteins- Low in one or more of the essential amino acids ANIMAL PROTEINS SOURCE TYPE OF CHON MISSING AA Egg Complete None Milk (Dairy) Complete None Meat, Fish Complete None VEGETABLE PROTEINS SOURCE TYPE OF CHON MISSING AA Wheat Incomplete Lysine Corn Incomplete Lysine &Tryptophan Rice Incomplete Lysine Beans Incomplete Methionine &Tryptophan Peas Incomplete Methionine •The two vegetable proteins are called complementary proteins. –Ex. Rice and Beans -C-C-C-N-C-N = N+ Basic Arg R N -OH Tyr K -C-C-C-C-NH3+ His Phe H -C-C-CONH2 Asn N Gln Q Amide F Asp D Glu E Acidic -C-COOH Central line Gly G Ala -H AA Val -C-C-COOH V C C -C -CH3 Ser S Cys -C-C Thr OH T Met M -C-C-S-C -C-OH Polar Y -C-CONH2 -C- -C-C C N N+ Non-polar This is NOT a metabolic pathway Trp W -C-C- Lys Amino Acid Subway Map Aromatic Hydroxy Sulfur Ile Aliphatic I Leu C -C-C-C C -C-SH L C -C-C-C C C C HN C-COOH Pro P Imino, Circular Classification of Amino Acids by Polarity NONPOLAR POLAR Acidic Asp Neutral Basic Asn Ser Arg Cys Tyr His Gln Thr Lys Glu Gly Ala Ile Phe Trp Val Leu Met Pro 20