Amino Acids - L1) Amino acids 2.pdf

Amino Acids Editing File Objective: Color Index: 1. What are amino acids? Main text (black) 2. General structure. Female slides (pink) 3. Classification of amino acids Mal...

Amino Acids Editing File Objective: Color Index: 1. What are amino acids? Main text (black) 2. General structure. Female slides (pink) 3. Classification of amino acids Male slides (blue) 4. Optical properties Important (red) 5. Amino acids configuration Dr’s Notes (green) 6. Non-standard amino acids Extra Info (grey) 7. Derivatives of amino acids  Amino Acids? Chemical units that combine to form a protein. The building blocks of protein. Carboxyl group Amino acids are a type of organic acid that contain ( COOH ) Amino group ( NH2 ) Amino acids play central roles Building Blocks of proteins intermediates in metabolism Human can produce about half of amino acids. - Human produce 11 amino acids and the rest 9 amino acids supplied in the food Others? Must be supplied in the food When proteins are digested or broken down, amino acids are left General Structure 01 02 Hydrogen atom Carboxyl group (H) (COOH) 03 04 Amino group (NH₂) Side chain (R) All Amino acid have primary Distinctive in each amino Amino group (except for acid, which gives the amino proline which has a acid its unique structure and secondary amino group). set of characteristics. Zwitterion Neutral amino acid with both positive charge and negative charge Amino group Carboxyl group (NH₃⁺) (COO⁻) The net change = ZERO Amino group with an ionized (charged) R can not be zwitterion in the neutral PH Team 444: Zwitterion means hybrid because it has +ve and -ve changed  Isoelectric point (Pi) The PH at which the molecules carries no net charge (neutral), and becomes a zwitterion. In acidic solution Law PH , Cationic ( Becomes Cation ) In Basic solution high PH , Anionic ( Becomes Anion ) Each molecule has its own isoelectric point depending on the side chain (R). Isoelectric point (Pi) cationic Zwitterion Anionic Low PH PH=PI High PH (high conc. of proton H⁺) (low conc. of proton H⁺) Positively Charged No net charge Negatively Charged The carboxylic acid will gain proton Zwitterion is used to describe The amino group will lose a proton (H⁺), and lose its negative charge. the molecule. (H⁺) and lose its positive charge. The overall charge= +ve (Cationic) Isoelectric point is used to The overall charge= -ve (Anionic) describe the PH level.  pK Value Also known as pKa or (acid dissociation constant) The ability of an acid to donate a proton (dissociate) α-amino group α-carboxylic group 9.4 pKa 2.2 Team 441: pKa let us know how strong or weak an acid High pKa = Low acidity = Low conc of proton  Team 438: Titration curve of glycine Pk = measurement of the acidity of the GROUP Ph: measurement of the acidity of the SOLUTION When pk= ph the group starts donating hydrogen instead of the medium pK1 PI pK2 pH at which 50% of 100% of the pH at which 50% of molecules are in cation molecules zwitterion molecules are in anion form and 50% are in net charge is zero form and 50% are in zwitterion form zwitterion form. Buffering action is at its Buffering action is Buffering action is at its max at its min max pH = pk1 = 2.3 pH = PI = 5.9: All COOH pH = pk2 = 9.6 The COOH group in Glycine has became COO⁻, so there are no The ammonia group starts lower pk value, so it will donate its more protons to donate. 100% donating protons, and becomes NH₃ protons first to neutralize the OH- in of molecules are zwitterions. → NH₂. Zwitterions will lose a the medium, and becomes COO⁻. As positive charge, & anions are a result, zwitterions will be formed formed Buffering action is maximum around pK values and minimum at pI  PVT TIM HLL STC TAG ‫بڤت تيم هال‬ Cannot be made by the body Glu Ala AsAs PGAV PIL TM ‫قلّهـ على اساس‬ ‫)بجاف بيل تم( ولد عم‬ ‫بڤت تيم هال‬ Preduced by the body PGG CATS Sounds like (Big cat) (weak basic) Not essential Except in time of illness or stress Nonpolar amino acids Each amino acids does not bind or give off protons These amino acids promote or participate in hydrogen or ionic bonds. hydrophobic interaction Non polar amino acids in proteins found in aqueous solution, the side chains of the non polar amino acids tend to cluster together in the interior of the protein Extra to understand  Nonpolar amino acids The structure of proline amino acid differs from other non polar amino acids that the side chain of proline and its α-amino group form a ring structure (an imino group) All the amino acids have primary amino group, except proline has secondary amino group (an imino group) question says: how many amino acids in the human body? We choose 19 Because proline is an imino acid. If 19 is an option, otherwise 20 Polar amino acids Amino acids with acidic side chains Amino acids with basic side chains Aspartic and Glutamic acids are proton Histidine,Lysine and Arginine are donor proton acceptor At neutral pH, these amino acids are fully At neutral pH, Lysine and Arginine are ionized (negatively charged). So, they are fully ionized (positively charged) called aspartate and glutamate Team439: Histidine (Pk around 6) is a weak base and therefore when fully ionized it carries a neutral charge, (Zwitterion form)  Uncharged amino acids These amino acids have zero net charge an neutral pH The side chains of Cysteine and Tyrosine can lose a proton at an alkaline pH (high pH) Serine, Threonine and Tyrosine each contain a polar hydroxyl group that can participate in hydrogen bond formation The side chains of Asparagine and Glutamine each contain a carbonyl group and an amide group,both of which can also participate in hydrogen bonds Optical properties Asymmetric Symmetric Optically active Optically inactive The α-carbon is attached to four different The α-carbon is not attached to four chemical groups different chemical groups All mammalian amino acids are optically Glycine active except glycine They rotate the plane of polarized light in a polarimeter. Amino acids configuration L-Amino acids D-Amino acids Rotate polarized light to the left Rotate polarized light to the right All mammalian amino acids are found in D-amino acids are found in L-configuration antibiotics,plants and in cell wall of microorganisms Both L and D forms are chemically same  Non-standard amino acids Apart from the twenty standard amino acids, there are a vast number of "non-standard" amino acids These nonstandard amino acids are usually formed through modifications to standard amino acids you don’t have to memorize them if you know the standard amino acids Amino acids derivatives Name Derivative of Role Dopamine Neurotransmitters Tyrosine Thyroxine important thyroid hormone Histamine Histidine The mediator of allergic reactions Gamma Amino Butyric Acid Glutamic acid (GABA) Neurotransmitters  Take home messages Each amino acid has an 𝛂-carboxyl and a primary 𝛂-amino group (except for proline, which is an imino acid). At physiological pH., the 𝛂-carboxyl is dissociated and the 𝛂- amino group is protonated. Each amino acid also contains twenty distinctive side chains and the chemical nature of this side chain determines the function of the amino acid. All free amino acids and charged amino acids in peptide chains, can serve as buffers. Buffering action of proteins is maximum around pK values and minimum at isoelectric point. All mammalian amino acids are optically active except glycine. All mammalian amino acids are found in L-configuration.  MCQs 1- In acidic medium the molecule will be? A- Anion B- Cation C- Zwitterion D- None Flashcards 2- Buffering action reaches its …. Level around pK value A- Maximum B- Minimum C- Middle D- None 3- Which of the following is not optically active? A- Serine B- Histidine C- Glutamine D- Glycine 4- Which of the following is a derivative amino acid? 5- C 4- C A- Leucine B- Alanine C- Histamine D- Cysteine 3- D 5- What distinguishes the general structure of amino acids? 2- A 1- B A- The amino B- The carboxylic C- The side chain D- The central group acid group carbon atom  Team Leaders Saad AlDosari Nada AlMuhawwis Team Members Abdulrahman Alnasser Kadi Alluhayyan Jood Alqosi Turki Alanazi Norah Alrashid Horia Alotaibi Faisal Alnemri Rahaf Alshalawi Salman Almutairy Latifah Aldossary Mohammed Alqahtani Basma Albahkly Abdulaziz Alotaibi Renad Alsanad Fahad Almosa Rube Aldibas