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

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

3. 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

4. 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

5. 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

6. 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.

7. 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, base pairs per turn, distance between each base pair .33 nm

8. Structure of DNA S P B S P B

9. 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

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

11. 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

12. 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

13. 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

14. 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

15. 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