ASS.Lec. Suad Turky Ali Lec -5- AL-Ma’moon University College Medical Laberatory techniques Department Clinical biochemistry / Second stage ASS.Lec. Suad Turky Ali Lec -5-

Polar and neutral amino acids : Because of the presence of functional groups that are capable of hydrogen bonding , polar amino acids easily interact with water. They are (hydrophilic) or (water – loving) C- Acidic amino acids Two amino acids have side chains with carboxyl ate groups. Like :

D- Basic amino acids : Because amino acids bear positive charge at physiological pH. Therefore , they can form ionic bonds with acidic amino acids. Like :   L- licine And: At (ph) of (7) the carboxyl group of an amino acid is in its conjugate base form (-Coo-)and the amino group is in its conjugate acid form (-NH3). Thus each amino acid can behave as either an acid or a base. So : amino acids are (amphoteric) molecules that is , they can act as either an acid or a base. Neutral molecules that bear an equal number of positive and negative charges simultaneously are called (zwitterions) It is the (R) group however, that gives each amino acid its unique properties.

In addition to their primary function as component of proteins , amino acids have several other biological role : 1- several amino acids or their derivatives act as chemical messengers for example : glycine , thyroxine cathyrosive derivative produced in the thyroid gland of animals. and indole acetic acid (atryptophan) derivative found in plants are two examples of hormones. Hormones are chemical me ssages that are produced in one type of cell that regulate the function of other cells. 2- amino acids serve as precursors of a variety of complex nitrogen containing molecules. Example : include the nitrogenous base compo newts of nucleotides and the nucleic. 3- several amino acids act as metabolic intermediates . example : arginine - which is a component of the urea cycle the synthesis of urea , amolecule formed in vertebrate livers, is the principal mechanism for the disposal of nitrogenous waste.

Amino acids, classified according to their capacity to interaction or interact with water. nonpolar and neutral polar and neutral acidic basic

nonpolar neutral amino acids amino acids contain hydrocarbon (R) groups neutral in which R groups do not bear positive or negative charges. Nonpolar : because of their tendency to interact poorly with water so, nonpolar amino acids are (hydrophobic). Neu ral nonpolar amino acids : divided into : Aliphatic : has hydrocarbon chain like:  Or it has sulfur atom (s) like:  And :   &&& And: abbreviations of standard amino acids:

Amino acids Proteins may be broken into their constituent monomer molecules by hydrolysis. The amino acid products of the reaction constituent the amino acid composition of the protein. Each amino acid contains a central carbon atom (the α – carbon atom) to which an amino group (NH2-), a carboxyl group (-cooh), a hydrogen atom (H2) and an (R) (side chain) group attached.

Example :     α – Amino acid Note that (19) of the amino acids have the same general structure. The twentieth amino acid is (praline). Which is actually an α – imino acid since, it's side chain group is bonded to (nitrogen) as well as to the α – carbon. Because of its unusual structure, the presence of praline in a polypeptide has important structural consequences. Note : (20) amino acids found in protein.

Fetal hemoglobin (HBF) Fetal hemoglobin protein structure. Fetal hemoglobin or fontal hemoglobin , (also hemoglobin F or Hbf) is the main oxygen transport in the fetun during the last seven months of development in the uterus and in the newborn until roughly 6 months old . functionality , fetal hemoglobin differs most from adult hemoglobin in that it is able to bind oxygen with greater affinity than the adult form , giving the developing fetus better access to oxygen from the mothers blood stream. Most types of hemoglobin A , hemoglobin A2 , and hemoglobin F , are tetramers composed of four heme prosthetic group. Whereas adult hemoglobin is composed of two alpha (α) and two beta (β) subunits, fetal hemoglobin is composed of two alpha (α) and two gamma(γ) sbunits , commonly denoted as (α2 γ2). Because of its presence in fetal hemoglobin, the gamma subunits is commonly called the "fetal" hemoglobin subunit.

Thalassemia Thalassemias, are hereditary disorders characterized by a reduction in the rate of synthesis of one type of globin chain . Thus of there is a reduction in α – chain synthesis , the condition is a β – thalassemia, α – thalassemia appears to be the most common genetic disorder of humans. وهنا السبب هو نتيجة للطفرات الوراثية المؤثرة على منظمات وراثية genes regulators وليس نتيجة للطفرات المؤثرة على التراكيب الوراثية genes structural

sickle –cell anemia : Which is caused by a mutant hemoglobin. Human adult hemoglobin (Hba) is composed of the two identical α – chains and two identical β chains. Sickle – cell anemia results from a single amino substitution in the β – chain of Hba. Analysis of hemoglobin molecules of sickle – cell patients reveals that the only difference between Hba and sickle – cell hemoglobin (HBS) is at amino acid residue (6) in the β chain. HBA : VAL – HIS – LUE – THR – PRO – GLU – GLU – LYS HBS : VAL – HIS – LEU – THR – PRO – VAL – GLU – LYS We can say : (sickle –cell anemia disease) Individuals possessing the gene for sickle – cell hemoglobin produce β – chain with a valine at residue (6) instead of glutamic acid sickle – cell anemia disease called molecular diseases.

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