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Structure of Amino Acids

Molecular Biology. Structure of Amino Acids. Amino Acids. Amino acids are the structural building blocks ( monomers ) of proteins . There are twenty different kinds of amino acids used in proteins.

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Structure of Amino Acids

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  1. Molecular Biology Structure of Amino Acids

  2. Amino Acids • Amino acids are the structural building blocks (monomers) of proteins. • There are twenty different kinds of amino acids used in proteins. • Proteins are referred to as heteropolymers due the variety of amino acids involved in their structure.

  3. a-carbon Structure

  4. D-isomer L-isomer Amino Acids (cont’d.) • Amino acids, like carbohydrates, show isomerism. Proteins are only made up of amino acids which are L-isomers.

  5. Amino Acids (cont’d.) • At neutral pH’s amino acids exist in an ionised form and have both acidic and basic properties. This is because the carboxylic group donates hydrogen ions to the solution (acidic) whereas the amino group (NH2) attracts hydrogen ions from the solution.

  6. Amino Acids (cont’d.) • The repeating sequence of atoms along a proteins is referred to as the polypeptide backbone. Attached to this repetitive chain are the different amino acid side chains (R-groups) which are not involved in the peptide bond but which give each amino acid its unique property.

  7. Amino Acids (cont’d.) • Amino acids are grouped according to whether their side chains are:- • acidic • basic • uncharged polar • non polar

  8. AsparticAcid asp   Acidic Polar  GlutamicAcid glu Acidic Polar Acidic Amino Acids

  9. Lysine lys Basic Polar  Arginine arg   Basic Polar Basic Amino Acids

  10. Glutamine gln Neutral Polar Tyrosine  tyr   Neutral Polar Neutral Polar Amino Acids

  11. Isoleucine  ile Neutral Non-polar Methionine  met Neutral Non-polar Non Polar Amino Acids

  12. Amino Acids (cont’d.) • The type of side chain is very important as it affects the solubility of the amino acid. • Hydrophobic features include long non-polar (uncharged) chains or complex aromatic rings. • Hydrophilic features include additional carboxyl groups or amino groups not involved in peptide bonding which are ionised in solution.

  13. Amino Acids (cont’d.) • Amino acids link together by covalent peptide bonds. This involves a condensation /dehydration reaction. These bonds are very strong. When this takes place the charged amino and carboxylic groups disappear.

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