Under electron microscope the structures seen as rough endoplasmic reticulum

can be manutactured in the body. However, the major portions ottne methyl group shall have to be obtained trom tood, so ;hat methioinne is an essential amino acid The CH3 radical, thus obtained from the methionine, is utilized to synthesize compounds which contain methyl radicals in them. Thus, the CH3 radical of methionme is utilized to synthesize, choline adrenalin, creatine etc. The process of transfering the CH3 radical is called transmethylation. Besides, the methionine is usei in forming polypeptide chain as usual. After the CH3 group is removed, the methionine becomes homocysteine. Subsequently, from homocysteine, cysteine and cystine can be synthesized. The SH group of cysteine can participate in the disulphide linkage, as in insulin Many enzymes owe their enzyme activity because of the fact that they contain - SH (sulphydril group) within it This SH group is a part of cysteme. or cystme Cysteme can be decarboxylated to produce mercaptoethylamine, which is a part of coenzyme A. Cysteine can be converted into taurine. Taurine conjugates with cholic acid to produce taurocholic aci d, which is a bile acid. Excess cysteine is converted into pyruvic acid. Preliminary steps include removal of NH2 and SH groups. It may be noted that cysteme and cystine are not essential amino acids CREATINE AND CREATININE Creatine is chemically methyl guanido acetic acid, whereas creatinine is anhydride of creatine Thei structures are given below. Mark, the creatine molecule contains one guanidine group, one acetic acid and one methy 'adical,Synthesis Creatine can be synthesized in the body. From isotopic experiments, it has been shown that, two amino acids, glycininine and argmine form guanido acetic acid portion whereas the CH3 group is donated by methionme by iransmethylation. The guanidoacetic acid is synthesized in the kidney and the transmethylation occurs in the liver Occurrence Most of the creatine in our body is in the form of creatine phosphate. Creatine phosphate occurs in the muscles where it acts as a high energy phosphate compound and plays a part in the contraction of skeletal muscles. A part of the creatine phosphate of the skeletal muscle is converted into creatinine and then removed from the body, via urine, as urinary creatmine The normal blood creatmine concentration is between 0.6 -1.5 mg/100 ml. One of the early signs of renal failure is -ise of creatinine concentration of blood Creatine normally is not excreted via urine (but creatinine is promptly excreted). Creatinuria, that is, excretion of creatine via urine is a recognized entity and occurs in some diseases and in special situations even in healthy persons (e.g. puerperium). SUMMARY & HIGHLIGHTS The size of amino acid pool m our body is constant; fresh amino acids are poured into it and amino acids also leave the pool to form body proteins. Amino acids are required fo protein synthesis; this is the anabolic aspect of amino acid metabolism. Only that portion of the amino adds which become excess, undergo catabolism. The NH2 group which leaves the amino acid can (i) become urea or (ii) combine with a ketoacu to form an amino acid. The urea synthesis occurs by a series of steps, collectively called Krebs-Hensehte cycle. The ketoacu which is formed after the loss of NH2 group merges either into the stream of glucose or fat metabolism; they are accordingly called glucogenic or ketogenic aminoacids. Individual amino acids : (i) Phenyl alanine or tyrosine. Phenyl alanine eithe becomes tyrosme or catabohzed Tyrosme D either becomes adrenalm/thyroxme/dopa fumarate and oxaloacetate, metabolic blocks in the above scheme are well known (phenyl ketonuria, albinism, alkaptonuria). (2) From tryptophan - 5 HT formed. NUCLEIC ACID I. Introduction. Elementary chemistry : Structure of a nucleotide : (a) base. (b) sugar, (c) phosphoric acid. DNA molecule. The double helix. RNA molecule. The single helix. Different types of RNA functions of nucleic acids : DNA : (a RNA production; Duplication and genetic copying. Genetic code. Prevention of mutation. RNA: (oJ Protein synthesis N. Virus. Metabolism of purine and pynmidine bases. Gout. Introduction Nucleic acids are of two types, viz, deoxyribonucleic acu (DNA) and ribonucleic acid (RNA). The DNA is found in the nucleus of the cells whereas the RNA is found mostly in the cytoplasm . However, small amounts of RNA are also found in the nucleolus of the cell. In the light microscopes, what are seen as chromosomes are essentially DNA molecules (plus little protein). Under electron microscope the structures seen as rough endoplasmic reticulum (the roughness is due to the fact that from the endoplasmic reticulum, RNA molecules, sRNA to fle specific, hang like so many needles) contain RNA molecules The DNA molecules can be regarded as somewha immortal The DNA molecular strands of my father and my mother united to form the DNA of the fertilized ovum m my mother's Fallopian tube, That single cell divided and redivided to form some 40 trillion cells constituting my body. Thus my DNA strands are the copies of the blended original from two sources, my father and my mother and contains little bit from my father and little bit from my mother. Also remember, during cell division every DNA strand physically divides and moves into !he daughter cells. My mother and my father got their DNA from their parents. Therefore, my DNA strands have come from Jhose of my grand parents In this way, it can be visualized that building materials of these DNAs of