Reminder-four classes of large biomolecules Carbohydrates/polysaccharides Lipids Proteins/polypeptides Nucleic acids/polynucleotides-information storage, hard drives for living systems

Two Types Nucleic Acid DNA and RNA Function: Information Storage And Control DNA 1 Synthesis of mRNA Two Types Nucleic Acid DNA and RNA mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Ribosome Figure 5.25 DNA → RNA → protein. 3 Synthesis of protein Amino acids Polypeptide

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

Figure 5.26 Components of nucleic acids. Sugar-phosphate backbone 5 end Nitrogenous bases Pyrimidines 5C 3C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines 5C 1C Phosphate group 3C 5C Sugar (pentose) Adenine (A) Guanine (G) 3C (b) Nucleotide Figure 5.26 Components of nucleic acids. Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components

RNA Structure Individual chains in cells Aka “single-stranded”: ssRNA Chains generally from 50-5000 nucleotides Distributed throughout the cell

RNA molecules fold up on themselves Secondary structure refers to folding pattern Confers unique shape Primary structure is the 5’ to 3’ sequence of bases 5’ 3’

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 “double-stranded”: dsDNA Not as flexible as RNA Chains can be very long 120,000,000 nucleotides Distributed throughout the cell Sequestered DNA Structure

Individual nucleotides Mononucleotides Have different functions Energy carriers Help with enzyme reactions as cofactors Signalling