Cellular Metabolism Chapter 4 Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nucleic Acids and Protein Synthesis Instruction of cells to synthesize proteins comes from a nucleic acid, deoxyribonucleic acid (DNA)

Genetic Information Genetic information – instructs cells how to construct proteins; stored in DNA Gene – segment of DNA that codes for one protein Genome – complete set of genes Genetic Code – method used to translate a sequence of nucleotides of DNA into a sequence of amino acids

Animation: DNA Structure Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

Structure of DNA DNA Nucleotide: Building blocks of DNA Pentose (5 carbon) sugar deoxyribose Nitrogenous base connected to the 1’ carbon: adenine, guanine, cytosine, thymine Phosphate group connect to the 5’ carbon 3’ carbon is site of next DNA nucleotide attachment RNA Nucleotide: Building blocks of RNA Pentose (5 carbon) sugar ribose (hydroxyl group instead of hydrogen) Nitrogenous base connected to the 1’ carbon: adenine, guanine, cytosine, uracil Phosphate group connected to the 5’ carbon 3’ carbon is site of next RNA nucleotide attachment

Structure of DNA 3. Purines 4. Pyrimidines 5. Sugar-Phosphate Backbone adenine and guanine composed of two linked rings which contain nitrogen atoms 4. Pyrimidines cytosine, uracil, thymine thymine is only in DNA nucleotides uracil is only in RNA nucleotides composed of s single ring which contains nitrogen atoms 5. Sugar-Phosphate Backbone Phosphate at the 5’ position of one nucleotide attaches at the hydroxyl at the 3’ position of the next nucleotides to form the backbone of a DNA strand from which the nitrogenous bases will extend.

Structure of DNA 6. Complementary Nitrogenous Bases Two DNA strands bind when their nitrogenous bases complementary base pair Adenine bonds with thymine by forming 2 hydrogen bonds (A-T) Guanine bonds with cytosine by forming 3 hydrogen bonds which makes a stronger bond (G-C) During transcription the uracil on the RNA will form 2 hydrogen bonds with adenine on the DNA 7. Antiparallel Strand Orientation When 2 DNA strands are paired, the 5’ end of one strand is matched with the 3’ end of the other 2 strands are parallel but oriented in opposite directions “antiparallel” 8. Double Helix A twisted ladder, not symmetrical Contains a major groove (wide) and minor groove (narrow) Transcription occurs at the major groove Right-hand turn, 10-10.5 base pairs per turn, distance between each base pair .33 nm

Structure of DNA S P B S P B

Structure of DNA Thymine (T) Cytosine (C) Guanine (G) Adenine (A) P T Thymine (T) Cytosine (C) Guanine (G) Adenine (A) Polynucleotide strands Segment of DNA molecule Chromatin Globular histone proteins Interphase chromosome Metaphase (c) (b) (a) Hydrogen bond

DNA Replication Hydrogen bonds break between bases Double strands unwind and pull apart New nucleotides pair with exposed bases Controlled by DNA polymerase

DNA Replication interphase Mitosis C A T G S Prophase Metaphase Anaphase Telophase Newly forming DNA molecules G1 Cytokinesis Restriction checkpoint Apoptosis Original DNA molecule S phase: genetic material replicates G2 phase G1 phase: Cell growth Proceed to division Remain specialized G2 interphase Mitosis

Animation: DNA Replication Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

DNA Replication DNA Helicase Topoisomerase (DNA Gyrase) Enzyme that binds to replication origin on DNA and begins to unwind the DNA helix by breaking hydrogen bonds between the bases Typically happens at A-T due to 2 hydrogen bonds Topoisomerase (DNA Gyrase) Enzyme that relieves tension in DNA by working ahead of helicase and cutting the sugar phosphate backbones so DNA can untwist and relieve tension Once tension is relieved it rejoins the sugar phosphate backbones Single Stranded Binging Proteins Prevents the rejoining of DNA by binding to the single strands near the replication fork RNA Primase Enzyme that builds short complementary segments of RNA (primers) on the template strands

DNA Replication 5. DNA Polymerase III 6. Nucleoside Triphosphates Enzyme that adds nucleotides starting at the end with the RNA primers One polymerase is needed on the leading strand Many polymerases are needed on the lagging strand since it is in the opposite direction of the movement of the replication fork 6. Nucleoside Triphosphates Similar to the typical DNA nucleotides, but have 3 phosphates instead of one 7. Leading Strand New DNA strand built in the same direction as the replication fork Built continuously in one long segment with one primer 8. Lagging Strand New DNA strand that is built in the opposite direction of the replication fork Built using short fragments of DNA (Okazaki) Built discontinuously away from replication fork

DNA Replication 9. DNA Polymerase I 10. DNA Ligase 11. Exonucleases Enzyme that comes in and removes every RNA nucleotide in each primer and replaces them with the appropriate FNA nucleotide Used many times on the lagging strand Used once on the leading strand 10. DNA Ligase Enzyme that joins unattached sections of DNA by forming phosphodiester bonds Attaches together the Okazaki fragments Used many times on lagging strand Used once on leading strand 11. Exonucleases Repair mechanism that allow mismatched DNA nucleotides to be removed and replaced with correct ones