One is the minimum and two is the maximum numbers an electron orbital can have. Valency is the number of covalent bonds a molecule can make. The body defends itself from free radicals using antioxidants. Primary structure is a simple sequence of repeating units. Secondary structure is the folding of primary structure into helices and aheets which are regular in structure. Tertiary structure is any subsequent folding. Quarternary structure is when two or more molecules are bonded together. Primary structure is held together by covalent bonds. DNA is a double helix held together by hydrogen bonds. Primary structure is the basis for the genetic code. The code consists of codons and results in the translation of mRNA to protein. Transcription is the production of mRNA. Translation is the assembling of a protein using mRNA. Cancer is the unregulated control of mitosis. --Nurse207 17:14, 17 August 2009 (BST)
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