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Concept 5.5: Nucleic acids store and transmit hereditary information Chapter 5-5 The Structure and Function of Large Biological Molecules PowerPoint® Lecture Presentations for • Chromosomes contain one long molecule of DNA • Each chromosome contains multiple genes – Genes are the AA sequences on DNA that code for individual proteins NUCLEIC ACIDS Biology DNA RNA Protein – Genes are made of DNA, a nucleic acid Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Roles of Nucleic Acids • There are two types of nucleic acids: – Deoxyribonucleic acid (DNA) The Roles of Nucleic Acids • There are two types of nucleic acids: – Ribonucleic acid (RNA) • provides directions for its own replication • directs synthesis of messenger RNA (mRNA) • carries the code for making one polypeptide from one gene in the nucleus to ribosomes in the cytoplasm • through mRNA, controls protein synthesis • functions as a part of ribosomes • is passed from one generation of cells to the next • brings amino acids to the ribosomes • can be used to determine how closely related organisms are Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-26-1 Fig. 5-26-2 DNA 1 Synthesis of mRNA in the nucleus DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS mRNA NUCLEUS CYTOPLASM CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm via nuclear pore 1 Fig. 5-26-3 The Structure of Nucleic Acids DNA 1 Synthesis of mRNA in the nucleus • Nucleic acids are polymers called polynucleotides mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm via nuclear pore Ribosome 3 Synthesis of protein – nucleotides = the monomers of polynucleotides (DNA & RNA) • Each nucleotide consists of a nitrogenous base, a pentose (5-carbon) sugar, and a phosphate group • nucleoside = the portion of a nucleotide without the phosphate group Amino acids Polypeptide Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-27ab Nucleotide Monomers 5' end 5'C Nucleotide 3'C Nucleoside Nitrogenous base Phosphate group 3'C Sugar (pentose) 3'C – Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring of C & N – Purines (adenine and guanine) have two rings: a six-membered ring fused to a fivemembered ring 5'C 5'C • There are two families of nitrogenous bases: 3' end • In DNA, pyrimidines pair with purines C---G T---A (a) Polynucleotide, or nucleic acid Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-27c-1 Nitrogenous bases The nitrogen in the nitrogenous base acts as a proton acceptor Nucleotide Monomers Pyrimidines • There are two pentose sugars found in nucleic acids • In DNA, the sugar is deoxyribose DNA Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) --contains A, T, G, C • in RNA, the sugar is ribose Purines Sugars RNA --contains A, U, G, C Adenine (A) Guanine (G) Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: nitrogenous bases Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 2 Nucleotide Monomers Nucleotide Polymers • Phosphate group • Attached to the #5 C on the sugar Phosphate group 5'C • Acts as a proton donor & is the functional group that makes DNA & RNA acids • Phosphodiester linkages – Adjacent nucleotides are joined by covalent bonds that form between the –OH group on the 3′ carbon of one nucleotide and the phosphate on the 5′ carbon on the next – These links create a backbone of sugarphosphate units with nitrogenous bases as appendages • The sequence of bases along a DNA or mRNA polymer is unique for each gene Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The DNA Double Helix The DNA Double Helix • A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix • The sugar-phosphate backbones are on the OUTSIDE of the helix and are held together by covalent bonds • The nitrogen bases are in the middle and pair up to connect the 2 sides using hydrogen bonds • In the DNA double helix, the two backbones run in opposite 5′ → 3′ directions from each other, an arrangement referred to as antiparallel 5' end The complementary strands are used as templates to replicate the DNA, resulting in two identical copies of the original DNA The structure of the DNA accounts for its function in transmitting genetic information to new cells. A—T – C—G Complementary base pairing • van der Waals forces between the stacked bases also help to hold the strands together Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-28 – Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 3' end DNA and Proteins as Tape Measures of Evolution Sugar-phosphate backbones Base pair (joined by hydrogen bonding) Old strands • The linear sequences of nucleotides in DNA molecules are passed from parents to offspring • Two closely related species are more similar in DNA than are more distantly related species Nucleotide about to be added to a new strand 3' end • Molecular biology can be used to assess evolutionary kinship 5' end New strands 5' end 3' end 5' end 3' end Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 3 The Theme of Emergent Properties in the Chemistry of Life: A Review Quick Quiz • Higher levels of organization result in the emergence of new properties 1. In a DNA double helix, a region along one DNA strand has the following sequence of nitrogenous bases: 5’ –TAGGCCT- 3’ – Water’s behavior results from interactions of its molecules – Chemical groups on carbon skeletons determine the behavior of larger molecules 3’ –ATCCGGA- 5’ What would be the complementary strand? – Polymers have properties not found in their monomers • Organization is the key to the chemistry of life Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Quick Quiz Quick Quiz 2. Suppose a substitution occurred in one DNA strand of the double helix, resulting in : 3. Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA? 5’ –TAAGCCT- 3’ a) 5’-purine-pyrimidine-purine-pyrimidine-3’ with 3’-purine-pyrimidine-purine-pyrimidine-5’ 3’ –ATTCGGA–ATCCGGA- 5’ 5’ Identify the mismatched pair of nucleotides. b) 5’-AGCT-3’ with 5’-TCGA-3’ If the modified top strand were replicated, what would be the complementary strand? c) 5’-GCGC-3’ with 5’-TATA-3’ d) 5’-ATGC-3’ with 3’-TCGA-5’ e) All of these pairs are correct. 4. Construct a table that organizes the following terms, and label the columns and rows: Phosphodiester linkages Peptide bonds Polypeptides Monosaccharides Triglycerides Nucleotides Glycosidic linkages Ester linkages Polynucleotides Amino acids Polysaccharides Fatty acids 4. Construct a table that organizes the following terms, and label the columns and rows: 4 You should now be able to: Fig. 5-UN2a 5. Distinguish between the following pairs: a) pyrimidine and purine b) nucleotide and nucleoside c) ribose and deoxyribose d) the 5′ end and 3′ end of a nucleotide Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-UN2b 5