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Reminder-four classes of large biomolecules • • • • Carbohydrates/polysaccharides Lipids Proteins/polypeptides Nucleic acids/polynucleotides DNA Two Types Nucleic Acid 1 Synthesis of mRNA Function: Information Storage And Control mRNA NUCLEUS CYTOPLASM mRNA DNA and RNA 2 Movement of mRNA into cytoplasm Ribosome 3 Synthesis of protein Polypeptide Amino acids Components of nucleic acids • Nucleic acids are polymers • Nucleotides are the monomers • Each nucleotide consists of a base, a sugar and a phosphate • But the base plus the sugar without the phosphate is called a nucleoside • Bases are purines (Pu) or pyrimidines (Pyr) • Sugars are either ribose or 2-deoxyribose Phosphodiester Bond • Links nucleotides together • Sugar and phosphate involved • This example is a 3’-5’ bond • Gives two distinct ends 5 end Sugar-phosphate backbone Nitrogenous bases Pyrimidines 5C 3C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines 5C 1C 5C 3C Phosphate group 3C Sugar (pentose) Guanine (G) Adenine (A) (b) Nucleotide Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) (c) Nucleoside components Ribose (in RNA) RNA Structure • Individual chains in cells • Aka “single-stranded”: ssRNA • Chains generally from 505000 nucleotides • Distributed throughout the cell RNA molecules fold up on themselves 5’ 3’ • Secondary structure refers to folding pattern • Confers unique shape • Primary structure is the 5’ to 3’ sequence of bases DNA structure-different from RNA • Two molecules interact to form double strand Important features of the double helix • Antiparallel strands • Bases on the inside • Chain held together by hydrogen bonds • Watson-Crick base pairs AT and GC are the Watson-Crick base pairs Complementary DNA Structure • Almost always double helix • Aka “doublestranded”: dsDNA • Not as flexible as RNA • Chains can be very long 120,000,000 nucleotides • Distributed throughout the cell • Sequestered Individual nucleotides • • • • • Mononucleotides Have different functions Energy carriers Help with enzyme reactions as cofactors Signalling