Science, Part 54
Question 1: Define nucleic acids and discuss their significance in biochemistry.
Answer 1: Nucleic acids are polymers composed of many smaller nucleotides which can be further broken down to phosphoric acid, organic bases, amines, and deoxyribose or ribose. The nucleotides link to form the polymers in an alternating sequence of phosphate units and sugar units. A nucleic acid containing deoxyribose as its sugar is deoxyribonucleic acid, or DNA. If ribose is the sugar, the compound is ribonucleic acid, or RNA. Nucleic acids are important substances in biochemistry; DNA is the fundamental constituent of genes carrying hereditary information and occurs in a complex molecular arrangement known as the double helix. RNA is a compound essential to the proper formation and utilization of proteins within cells and is found in several varieties including the most common tRNA (transfer RNA) and mRNA (messenger RNA).
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Question 2: Describe codons and discuss their function.
Answer 2: Codons are long molecules formed of nucleotides and found in mRNA. Each codon is specific to the protein in whose synthesis it plays a lead role; each one has unique properties such as molecular weight. Codons are long because they contain three nucleotides for each amino acid required by their target protein. They are attached to ribosomes, which can move through several codons of the mRNA during protein synthesis. The ribosome chemically activates the appropriate codon to form amino acids in proper sequence for the necessary protein. It is a codon which eventually signals the completion of the protein and the separation of the peptide chain from the ribosome.
Question 3: Describe protein synthesis.
Answer 3: One of the most fundamental processes for life, protein synthesis, is a complex series of reactions involving large compounds. The synthesis occurs at the surface of ribosomal RNA (rRNA) particles suspended in the cytoplasm of cells. Amino acids bonded to transfer RNA (tRNA) are brought to the sites and the translation of codons into a sequence of amino acids begins if the required compounds are present. If all requirements are met, a series of enzyme-catalyzed steps begins to form long peptide chains. The process begins with the initiation step and concludes with termination, at which point the protein is separated from the rRNA. Most proteins are not yet in the form needed by the cell and are modified by more complex reactions to produce the needed protein.
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