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CAMPBELL BIOLOGY TENTH EDITION Global Edition Reece • Urry • Cain • Wasserman • Minorsky • Jackson 5 Biological Macromolecules 黃章文 and Lipids Chang-Wen Huang Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick © 2014 Pearson Education, Inc. Assistant Professor [email protected] Lab. Marine Molecular Genetics, Breeding and Biotechnology Department of Aquaculture, College of Life Sciences National Taiwan Ocean University The Molecules of Life Overview All living things are made up of four classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids. Macromolecules are large molecules composed of thousands of covalently connected atoms. Molecular structure and function are inseparable. 2 Why do scientists study the structures of macromolecules? 為何科學家們研究大分子結構? Macromolecules are polymers, built from monomers Polymers A long molecule consisting of many similar building blocks. These small building-block molecules are called monomers. Three of the four classes of life’s organic molecules are polymers. 1) Carbohydrates 2) Proteins 3) Nucleic acids © 2011 Pearson Education, Inc. 5 The Synthesis and Breakdown of Polymers A dehydration reaction occurs when two monomers bond together through the loss of a water molecule. Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction. © 2011 Pearson Education, Inc. 6 Dehydration reaction: synthesizing a polymer 1 2 3 4 Unlinked monomer Short polymer Dehydration removes a water molecule. Forming a new bond Longer polymer 1 2 3 4 7 Hydrolysis: breaking down a polymer 1 2 3 4 Hydrolysis adds a water molecule, breaking a bond. 1 2 3 4 8 The Diversity of Polymers Each cell has thousands of different macromolecules. HO Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species. An immense (huge) variety of polymers can be built from a small set of monomers. © 2011 Pearson Education, Inc. 9 Concept Check 5.1 1. What are the four main classes of large biological molecules? Which class does not consist of polymers? 2. How many molecules of water are needed to completely hydrolyze a polymer that is ten monomers long? 3. WHAT IF? If you eat a piece of fish, what reactions must occur for the amino acid monomers in the protein of the fish to be converted to new proteins in your body? Carbohydrates serve as fuel and building material Carbohydrates Include sugars and the polymers of sugars. The simplest carbohydrates are monosaccharides, or single sugars. Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks. © 2011 Pearson Education, Inc. 13 Sugars (Mono-) Monosaccharides have molecular formulas that are usually multiples of CH2O. Glucose (C6H12O6) is the most common monosaccharide. Monosaccharides are classified by The location of the carbonyl group (as aldose or ketose). The number of carbons in the carbon skeleton. © 2011 Pearson Education, Inc. 14 Figure 5.3 Aldoses (Aldehyde Sugars) Ketoses (Ketone Sugars) Trioses: 3-carbon sugars (C3H6O3) 甘油酸 Glyceraldehyde Dihydroxyacetone 二羥基丙酮 Pentoses: 5-carbon sugars (C5H10O5) 核糖 Ribose Ribulose 核酮糖 Hexoses: 6-carbon sugars (C6H12O6) Fructose Glucose Galactose Fructose 15 Figure 5.4 1 2 6 6 5 5 3 4 4 5 1 3 2 4 1 3 2 6 (a) Linear and ring forms 6 5 4 Though often drawn as linear skeletons, in aqueous solutions many sugars form glucose rings (carbon 1 bonds to the oxygen attached to carbon 5). 1 3 2 (b) Abbreviated ring structure Monosaccharides serve as a major fuel for cells and as raw material for building molecules. 16 17 Maillard Reaction 受熱的過程中會產生褐色物質,讓食物具有特殊的外觀,而 且形成特殊的風味,此稱之梅納反應 (非酵素性褐化反應)。 最早由法國人梅納氏在1912年提出,影響很多食品的製造和 儲存。 包括糖與碳水化合物的焦化作用,以及碳水化合物和蛋白質 、胺基酸等加熱處理或儲存後產生的反應。這兩種化學反應 都會產生褐色的物質,通常又稱作黑色素。 例如葡萄糖單獨在攝氏180度下加熱,可以產生焦糖香氣, 如果和離胺酸一起加熱,就會發出像麵包的香氣,和纈胺酸 一起加熱,也會形成類似巧克力的香氣。若缺乏非酵素性褐 化反應,那麼這些烘焙食品的吸引力,也會受到影響。 18 Sugars (Di-) A disaccharide is formed when a dehydration reaction joins two monosaccharides. This covalent bond is called a glycosidic linkage (糖苷鍵). © 2011 Pearson Education, Inc. 19 Figure 5.5 1–4 glycosidic 1 linkage 4 Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose 1–2 glycosidic 1 linkage 2 Glucose Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose 20 Sugars (Poly-) • Polysaccharides, the polymers of sugars, have storage and structural roles. • The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages. © 2011 Pearson Education, Inc. 21 Storage Polysaccharides • Starch, a storage polysaccharide of plants, consists entirely of glucose monomers. • Plants store surplus starch as granules within chloroplasts and other plastids (細胞質體). • The simplest form of starch is amylose. © 2011 Pearson Education, Inc. 22 Figure 5.6 Chloroplast Starch granules Amylopectin Amylose (a) Starch: 1 m a plant polysaccharide Mitochondria Glycogen granules Glycogen (b) Glycogen: 0.5 m an animal polysaccharide What’s cell? 23 • Humans and other vertebrates store glycogen mainly in liver and muscle cells. © 2011 Pearson Education, Inc. 24 Structural Polysaccharides • The polysaccharide cellulose is a major component of the tough wall of plant cells. • Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ. • The difference is based on two ring forms for glucose: alpha () and beta (). Animation: Polysaccharides © 2011 Pearson Education, Inc. 25 Figure 5.7 (a) and glucose ring structures 4 1 4 Glucose Glucose 1 4 (b) Starch: 1–4 linkage of glucose monomers Polymers with α-glucose are helical. 1 1 4 (c) Cellulose: 1–4 linkage of glucose monomers Polymers with β-glucose are straight. In straight structures, H atoms on one strand can bond with OH groups on other strands. 26 Figure 5.8 Cellulose microfibrils in a plant cell wall Cell wall Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants. Microfibril 10 m 0.5 m Cellulose molecules Glucose monomer 27 Enzymes that digest starch by hydrolyzing linkages can’t hydrolyze linkages in cellulose. Cellulose in human food passes through the digestive tract as insoluble fiber. Some microbes use enzymes to digest cellulose. Many herbivores, from cows to termites, have symbiotic relationships with these microbes. © 2011 Pearson Education, Inc. 28 Chitin Structural polysaccharide, is found in the exoskeleton of arthropods (節肢動 物). Chitin also provides structural support for the cell walls of many fungi. 29 29 Chitin 幾丁質(chitin)又稱 殼多醣、甲殼質、 甲殼素。 由N-乙醯-D-胺基葡 萄糖或D-胺基葡萄 糖以β -1,4糖苷鍵連 接而成之低聚合度 水溶性胺基多醣。 © 2011 Pearson Education, Inc. The structure of the chitin monomer 30 Figure 5.9b Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. 31 Concept Check 5.2 1. Write the formula for a monosaccharide that has three carbons. 2. A dehydration reaction joins two glucose molecules to form maltose. The formula for glucose is C6H12O6. what is the formula for maltose? 3. WHAT IF? After a caw is given antibiotics to treat an infection, a vet gives the animal a drink of “gut culture” containing various prokaryotes. Why is this necessary? 瘤胃開窗牛群在乳業先進國家早已是主要資產 乳牛每天採食18到 25公斤的乾物質, 可以生產20到40公 斤的牛乳。 乳牛的瘤胃是進行牧草纖維分解與飼糧 氮轉換的消化器官,藉由瘤胃內共生的 細菌(每毫升瘤胃液有一兆個)、原蟲( 每毫升瘤胃液有一百萬個)與真菌等微 生物所分泌的酵素,可提供牛隻所需的 脂肪酸和蛋白質量達50到65%之多。 Lipids are a diverse group of hydrophobic molecules Concept 5.3: Lipids are a diverse group of hydrophobic molecules • Lipids are the one class of large biological molecules that do not form polymers. • The unifying feature of lipids is having little or no affinity for water. • Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds. • The most biologically important lipids are: (1)Fats, (2)Phospholipids, (3)Steroids. © 2011 Pearson Education, Inc. 35 Fats • Fats are constructed from two types of smaller molecules: glycerol and fatty acids. Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon. A fatty acid consists of a carboxyl group attached to a long carbon skeleton. © 2011 Pearson Education, Inc. 36 Figure 5.10a hydroxyl carboxyl group group Fatty acid (in this case, palmitic acid) Glycerol One of three dehydration reactions in the synthesis of a fat. 37 • Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats. • In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride. © 2011 Pearson Education, Inc. 38 Figure 5.10b Ester linkage Fat molecule (triacylglycerol) 39 • Fatty acids vary in length (number of carbons) and in the number and locations of double bonds. • Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds. • Unsaturated fatty acids have one or more double bonds. Animation: Fats © 2011 Pearson Education, Inc. 40 Figure 5.11a Saturated fat Structural formula of a saturated fat molecule Space-filling model of stearic acid, a saturated fatty acid 41 Figure 5.11b Unsaturated fat Structural formula of an unsaturated fat molecule Space-filling model of oleic acid, an unsaturated fatty acid Cis double bond causes bending. 42 Saturated and Unsaturated Fatty Acids Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature. Most animal fats are saturated. Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature. Plant fats and fish fats are usually unsaturated. © 2011 Pearson Education, Inc. 43 • A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits. • Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen. • Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds. • These trans fats may contribute more than saturated fats to cardiovascular disease. © 2011 Pearson Education, Inc. 44 Certain unsaturated fatty acids are not synthesized in the human body. These must be supplied in the diet. These essential fatty acids include the omega-3 fatty acids, required for normal growth, and thought to provide protection against cardiovascular disease. © 2011 Pearson Education, Inc. 46 The major function of fats is energy storage. Humans and other mammals store their fat in adipose cells. Adipose tissue also cushions vital organs and insulates the body. © 2011 Pearson Education, Inc. 47 Phospholipids In a phospholipid, two fatty acids and a phosphate group are attached to glycerol. The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head. © 2011 Pearson Education, Inc. 48 Hydrophobic tails Hydrophilic head Figure 5.12 Choline Phosphate Glycerol Fatty acids Hydrophilic head Hydrophobic tails (a) Structural formula (b) Space-filling model (c) Phospholipid symbol Add to wather? 49 When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior. The structure of phospholipids results in a bilayer arrangement found in cell membranes. Phospholipids are the major component of all cell membranes. © 2011 Pearson Education, Inc. 50 Figure 5.13 Bilayer structure formed by selfassembly of phospholipids in an aqueous environment Hydrophilic head Hydrophobic tail WATER WATER 51 Steroids Steroids are lipids characterized by a carbon skeleton consisting of four fused rings. Cholesterol, an important steroid, is a component in animal cell membranes. Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease. © 2011 Pearson Education, Inc. 52 Figure 5.14 Cholesterol, a steroid Cholesterol is the molecule from which other steroids, including the sex hormones, are synthesized. Steroids vary in the chemical groups attached to their four interconnected rings (shown in gold). 53 Concept Check 5.3 1. Compare the structure of a fat (triglyceride) with that of a phospholipid? 2. Why are human sex hormones considered lipids? 3. WHAT IF? Suppose a membrane surrounded an oil droplet, as it does in the cells of plant seeds and in some animal cells. Describe and explain the form it might take. Proteins include a diversity of structures, resulting in a wide range of functions Concept 5.4: Proteins include a diversity of structures, resulting in a wide range of functions Proteins account for more than 50 % of the dry mass of most cells. Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances. © 2011 Pearson Education, Inc. 56 Figure 5.15a Enzymatic proteins Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Enzyme Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions. Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life. 57 Figure 5.15h Structural proteins Function: Support Examples: Keratin is the protein of hair, horns, feathers, and other skin appendages. Insects and spiders use silk fibers to make their cocoons and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues. Collagen Connective tissue 60 m 58 Figure 5.15b Storage proteins Function: Storage of amino acids Examples: Casein, the protein of milk, is the major source of amino acids for baby mammals. Plants have storage proteins in their seeds. Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo. Ovalbumin Amino acids for embryo 59 Figure 5.15f Transport proteins Function: Transport of substances Examples: Hemoglobin, the iron-containing protein of vertebrate blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across cell membranes. Transport protein Cell membrane 60 Figure 5.15c Hormonal proteins Function: Coordination of an organism’s activities Example: Insulin, a hormone secreted by the pancreas, causes other tissues to take up glucose, thus regulating blood sugar concentration. High blood sugar Insulin secreted Normal blood sugar 61 Figure 5.15g Receptor proteins Function: Response of cell to chemical stimuli Example: Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells. Signaling molecules Receptor protein 62 Figure 5.15d Contractile and motor proteins Function: Movement Examples: Motor proteins are responsible for the undulations of cilia and flagella. Actin and myosin proteins are responsible for the contraction of muscles. Actin Muscle tissue Myosin 100 m 63 Figure 5.15e Defensive proteins Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Antibodies Virus Bacterium 64 Polypeptides Polypeptides are unbranched polymers built from the same set of 20 amino acids. A protein is a biologically functional molecule that consists of one or more polypeptides. © 2011 Pearson Education, Inc. 65 Amino Acid Monomers Side chain (R group) • Amino acids are organic molecules with carboxyl and amino groups. • Amino acids differ in their properties due to differing side chains, called R groups. © 2011 Pearson Education, Inc. carbon Amino group Carboxyl group 66 Figure 5.16a Nonpolar side chains; hydrophobic Side chain Glycine (Gly or G) Methionine (Met or M) Alanine (Ala or A) Valine (Val or V) Phenylalanine (Phe or F) Leucine (Leu or L) Tryptophan (Trp or W) Isoleucine (Ile or I) Proline (Pro or P) 67 Figure 5.16b Polar side chains; hydrophilic Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) 68 Figure 5.16c Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Aspartic acid Glutamic acid (Glu or E) (Asp or D) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) 69 Amino Acid Polymers • Amino acids are linked by peptide bonds. • A polypeptide is a polymer of amino acids. • Polypeptides range in length from a few to more than a thousand monomers. • Each polypeptide has a unique linear sequence of amino acids, with a carboxyl end (C-terminus) and an amino end (Nterminus). © 2011 Pearson Education, Inc. 70 Figure 5.17 Peptide bond New peptide bond forming Side chains Backbone Amino end (N-terminus) Peptide bond Carboxyl end (C-terminus) 71 Protein Structure and Function • A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape. © 2011 Pearson Education, Inc. 72 Structure of a protein, the enzyme lysozyme Groove (a) A ribbon model Groove (b) A space-filling model 73 溶菌酶(Lysozyme) 分子量為14.4kDa的酵素,能夠催化肽聚糖 中N-乙醯胞壁酸和N-乙醯氨基葡萄糖殘基 間和殼糊精中N-乙醯葡糖胺殘基間的1,4-β 鏈的水解,而破壞細菌的細胞壁。 溶菌酶存在人體中之細胞分泌液,如唾液 、眼淚及其他一些體液中,也存在於粒線 體中的細胞質顆粒體中。蛋白中也有大量 的溶菌酶。 74 • The sequence of amino acids determines a protein’s three-dimensional structure. • A protein’s structure determines its function. © 2011 Pearson Education, Inc. 75 Figure 5.19 An antibody binding to a protein from a flu virus Antibody protein Protein from flu virus 76 Four Levels of Protein Structure • Primary structure of a protein is its unique sequence of amino acids. • Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain. • Tertiary structure is determined by interactions among various side chains (R groups). • Quaternary structure results when a protein consists of multiple polypeptide chains. © 2011 Pearson Education, Inc. 77 Primary structure Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word. Primary structure is determined by inherited genetic information. Animation: Primary Protein Structure © 2011 Pearson Education, Inc. 78 Figure 5.20a Primary structure Amino acids Amino end Primary structure of transthyretin Carboxyl end 79 Secondary structure The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone. Typical secondary structures are: 1) A coil called an helix. 2) A folded structure called a pleated sheet. Animation: Secondary Protein Structure © 2011 Pearson Education, Inc. 80 Figure 5.20c Secondary structure helix pleated sheet Hydrogen bond strand, shown as a flat arrow pointing toward the carboxyl end Hydrogen bond 81 Figure 5.20d Spiders secrete silk fibers made of a structural protein containing β pleated sheets, which allow the spider web to stretch and recoil 82 82 Tertiary structure Tertiary structure is determined by interactions between R groups. These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions. Strong covalent bonds called disulfide bridges may reinforce the protein’s structure. Animation: Tertiary Protein Structure © 2011 Pearson Education, Inc. 83 Figure 5.20f Tertiary structure Transthyretin (TTR) polypeptide Hydrogen bond Hydrophobic interactions and van der Waals interactions Disulfide bridge Ionic bond Polypeptide backbone 84 Quaternary structure When two or more polypeptide chains form one macromolecule. Transthyretin protein (four identical polypeptides) Animation: Quaternary Protein Structure © 2011 Pearson Education, Inc. 85 Figure 5.20b Tertiary structure Secondary structure Quaternary structure helix Hydrogen bond pleated sheet strand Hydrogen bond Transthyretin polypeptide Transthyretin protein 86 The complete protein Collagen is a fibrous protein consisting of three polypeptides coiled like a rope. Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains. © 2011 Pearson Education, Inc. 87 Figure 5.20h Collagen Journal of Structural Biology 142 (2003) 327–333 88 89 Sickle-Cell Disease: A Change in Primary Structure • A slight change in primary structure can affect a protein’s structure and ability to function. • Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin. © 2011 Pearson Education, Inc. 90 Figure 5.21 Sickle-cell hemoglobin Normal hemoglobin Primary Structure 1 2 3 4 5 6 7 Secondary and Tertiary Structures Quaternary Structure Function Molecules do not associate with one another; each carries oxygen. Normal hemoglobin subunit Red Blood Cell Shape 10 m 1 2 3 4 5 6 7 Exposed hydrophobic region Sickle-cell hemoglobin subunit Molecules crystallize into a fiber; capacity to carry oxygen is reduced. 10 m 91 What Determines Protein Structure? • In addition to primary structure, physical and chemical conditions can affect structure. • Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel. • This loss of a protein’s native structure is called denaturation. • A denatured protein is biologically inactive. © 2011 Pearson Education, Inc. 92 Figure 5.22 tu Normal protein Denatured protein 93 Protein Folding in the Cell • It is hard to predict a protein’s structure from its primary structure. • Most proteins probably go through several stages on their way to a stable structure. • Chaperonins are protein molecules that assist the proper folding of other proteins. • Diseases such as Alzheimer’s, Parkinson’s, and mad cow disease are associated with misfolded proteins. © 2011 Pearson Education, Inc. 94 Figure 5.23b Polypeptide Correctly folded protein Steps of Chaperonin 2 The cap attaches, causing 3 The cap comes Action: the cylinder to change off, and the 1 An unfolded polyshape in such a way that properly folded peptide enters the it creates a hydrophilic protein is cylinder from environment for the released. one end. folding of the polypeptide. 95 To determine and predict a protein’s structure X-ray crystallography Nuclear magnetic resonance (NMR) spectroscopy (does not require protein crystallization) Bioinformatics uses computer programs (from amino acid sequences) © 2011 Pearson Education, Inc. 96 Figure 5.24a What can the 3-D shape of the enzyme RNA polymerase II tell us about its function? EXPERIMENT Diffracted X-rays X-ray source X-ray beam Crystal Digital detector X-ray diffraction pattern Roger Kornberg利用X光結晶繪圖學技 術確立第II型RNA聚合酶的立體形狀。 Roger Kornberg (Nobel Prize in Chemistry, 2006) 使所有三種成分的複合體結晶化之後,瞄準穿過 結晶體的X光束,結晶體的諸原子使X光繞射成排 列整齊的陣列。數位偵測器將此記錄成為「X光 繞射圖形」的點狀圖案。 97 Figure 5.24b RESULTS RNA DNA RNA polymerase II 運用自X光繞射圖形的數據,以及化學方法所定出的 胺基酸序列,Roger Kornberg及其同事在電腦軟體的 輔助協助下,建構了該複合體的立體模型。 98 Concept Check 5.4 1. What parts of a polypeptide participate in the bonds that hold together secondary structure? Tertiary structure? 2. Thus far in the chapter, the Greed letters α and β have been used to specify at least three different pairs of structures. Name and briefly describe them. 3. WHAT IF? Where would you expect a polypeptide region rich in the amino acids valine, leucine, and isoleucine to be located in a folded polypeptide? Explain. Nucleic acids store, transmit, and help express hereditary information Concept 5.5: Nucleic acids store, transmit, and help express hereditary information The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene. Genes are made of DNA, a nucleic acid made of monomers called nucleotides. © 2011 Pearson Education, Inc. 101 The Roles of Nucleic Acids • There are two types of nucleic acids – Deoxyribonucleic acid (DNA) – Ribonucleic acid (RNA) • DNA provides directions for its own replication. • DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis. • Protein synthesis occurs in ribosomes. © 2011 Pearson Education, Inc. 102 Figure 5.25-3 DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Ribosome 3 Synthesis of protein Polypeptide Amino acids 103 The Components of Nucleic Acids • Nucleic acids are polymers called polynucleotides. • Each polynucleotide is made of monomers called nucleotides. • Each nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups. • The portion of a nucleotide without the phosphate group is called a nucleoside. © 2011 Pearson Education, Inc. 104 Figure 5.26 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) Ribose (in RNA) (c) Nucleoside components 105 • Nucleoside = nitrogenous base + sugar • There are two families of nitrogenous bases – Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring. – Purines (adenine and guanine) have a sixmembered ring fused to a five-membered ring. • In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose. • Nucleotide = nucleoside + phosphate group © 2011 Pearson Education, Inc. 106 Nucleotide Polymers • Nucleotide polymers are linked together to build a polynucleotide. • 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. © 2011 Pearson Education, Inc. 107 The Structures of DNA and RNA Molecules • RNA molecules usually exist as single polypeptide chains. • DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix. • In the DNA double helix, the two backbones run in opposite 5→ 3 directions from each other, an arrangement referred to as antiparallel. • One DNA molecule includes many genes. © 2011 Pearson Education, Inc. 108 • The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C). • Called complementary base pairing. • Complementary pairing can also occur between two RNA molecules or between parts of the same molecule. • In RNA, thymine is replaced by uracil (U) so A and U pair. © 2011 Pearson Education, Inc. 109 Figure 5.27 5 3 Sugar-phosphate backbones Hydrogen bonds Base pair joined by hydrogen bonding 3 5 (a) DNA Base pair joined by hydrogen bonding (b) Transfer RNA 110 DNA and Proteins as Tape Measures of Evolution • 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. • Molecular biology can be used to assess evolutionary kinship. © 2011 Pearson Education, Inc. 111 Concept Check 5.5 1. DRAW IT Go to Figure 5.24a and, for the top three nucleotides, number all the carbons in the sugars, circle the nitrogenous bases, and star the phosphates. 2. DRAW IT In a DNA double helix, a region along one DNA strand has this sequence of nitrogenous bases: 5’-TAGGCCT-3’. Copy this sequence, and write down its complementary strand, clearly indicating the 5’ and 3’ ends of the complementary strand. Genomics and proteomics have transformed biological inquiry and applications Concept 5.6: Genomics and proteomics have transformed biological inquiry and applications Once the structure of DNA and its relationship to amino acid sequence was understood, biologists sought to “decode” genes by learning their base sequences. The first chemical techniques for DNA sequencing were developed in the 1970s and refined over the next 20 years. 114 It is enlightening to sequence the full complement of DNA in an organism’s genome. The rapid development of faster and less expensive methods of sequencing was a side effect of the Human Genome Project. Many genomes have been sequenced, generating reams of data. Bioinformatics uses computer software and other computational tools to deal with the data resulting from sequencing many genomes. Analyzing large sets of genes or even comparing whole genomes of different species is called genomics. A similar analysis of large sets of proteins including their sequences is called proteomics MAKE CONNECTIONS Contributions of Genomics and Proteomics to Biology Paleontology Evolution Hippopotamus Medical Science Short-finned pilot whale Conservation Biology Species Interactions 118 DNA and Proteins as Tape Measures of Evolution Sequences of genes and their protein products document the hereditary background of an organism. Linear sequences of DNA molecules are passed from parents to offspring. We can extend the concept of “molecular genealogy” to relationships between species. Molecular biology has added a new measure to the toolkit of evolutionary biology. 119 Skills exercise Analyzing polypeptide sequence data ► Human (人類) ► Rhesus monkey (恆河猴) ► Gibbon (長臂猿) 120 The Theme of Emergent Properties in the Chemistry of Life: A Review Higher levels of organization result in the emergence of new properties. Organization is the key to the chemistry of life. © 2011 Pearson Education, Inc. 121 Welcome! Questions? Egg and Life 雞蛋, 從外打破是食物, 從内打破是生命。 人生, 從外打破是壓力, 從内打破是成長。 生物學期中考試公告 班級:水產養殖學系1A, 1B 日期:104年11月4日(三) 時間:18:30~20:00 人數:人 地點:群海廳CLS108 攜帶學分證。 座位分配(亂數逢機)。 103.10.03 天生比較聰明的學生 ,基測卻考得比較差 ,這是怎麼回事? 2013年02月08日 125 台灣研究學者針對779位的高中生 抽血採樣做分析,將被認為智商比 較高(認知能力好)的人,和智商 較低的人相比,後一群學生的平均 分數反而高8%,尤其是自然學科 更明顯,怎麼天生聰明的人,基測 反而考不好呢? 126 IQ高, 基測失常 智商高,認知佳 表現失靈 壓力 N=779 智商&認知普通 表現佳 127 多巴胺(Dopamine) C6H3(OH)2-CH2-CH2-NH2 一種腦內分泌物,屬於神經傳導 物質,可影響一個人的情緒。 改變放電速度,增加大腦運作。 128 關鍵的COMT基因 COMT基因 緩慢移除多巴胺 快速清除多巴胺 129