CampBellBiology in focus03

Nucleotide Polymers  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 of the next [r]

CAMPBELL BIOLOGY IN FOCUS Urry • Cain • Wasserman • Minorsky • Jackson • Reece Carbon and the Molecular Diversity of Life Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge © 2014 Pearson Education, Inc Overview: Carbon Compounds and Life  Aside from water, living organisms consist mostly of carbon-based compounds  Carbon is unparalleled in its ability to form large, complex, and diverse molecules  A compound containing carbon is said to be an organic compound © 2014 Pearson Education, Inc  Critically important molecules of all living things fall into four main classes  Carbohydrates  Lipids  Proteins  Nucleic acids  The first three of these can form huge molecules called macromolecules © 2014 Pearson Education, Inc Figure 3.1 © 2014 Pearson Education, Inc Concept 3.1: Carbon atoms can form diverse molecules by bonding to four other atoms  An atom’s electron configuration determines the kinds and number of bonds the atom will form with other atoms  This is the source of carbon’s versatility © 2014 Pearson Education, Inc The Formation of Bonds with Carbon  With four valence electrons, carbon can form four covalent bonds with a variety of atoms  This ability makes large, complex molecules possible  In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape  However, when two carbon atoms are joined by a double bond, the atoms joined to the carbons are in the same plane as the carbons © 2014 Pearson Education, Inc  When a carbon atom forms four single covalent bonds, the bonds angle toward the corners of an imaginary tetrahedron  When two carbon atoms are joined by a double bond, the atoms joined to those carbons are in the same plane as the carbons © 2014 Pearson Education, Inc Figure 3.2 Name Methane Ethane Ethene (ethylene) © 2014 Pearson Education, Inc Molecular Formula Structural Formula Ball-and-Stick Model Space-Filling Model  The electron configuration of carbon gives it covalent compatibility with many different elements  The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules © 2014 Pearson Education, Inc Figure 3.3 Hydrogen (valence  1) © 2014 Pearson Education, Inc Oxygen (valence  2) Nitrogen (valence  3) Carbon (valence  4)  Carbon atoms can partner with atoms other than hydrogen; for example:  Carbon dioxide: CO2  Urea: CO(NH2)2 © 2014 Pearson Education, Inc Figure 3.UN01 Estradiol Testosterone © 2014 Pearson Education, Inc Molecular Diversity Arising from Variation in Carbon Skeletons  Carbon chains form the skeletons of most organic molecules  Carbon chains vary in length and shape Animation: Carbon Skeletons © 2014 Pearson Education, Inc Figure 3.4 (a) Length Ethane (c) Double bond position Propane (b) Branching Butane © 2014 Pearson Education, Inc 1-Butene 2-Butene (d) Presence of rings 2-Methylpropane (isobutane) Cyclohexane Benzene Figure 3.4a (a) Length Ethane © 2014 Pearson Education, Inc Propane Figure 3.4b (b) Branching Butane © 2014 Pearson Education, Inc 2-Methylpropane (isobutane) Figure 3.4c (c) Double bond position 1-Butene © 2014 Pearson Education, Inc 2-Butene Figure 3.4d (d) Presence of rings Cyclohexane © 2014 Pearson Education, Inc Benzene  Hydrocarbons are organic molecules consisting of only carbon and hydrogen  Many organic molecules, such as fats, have hydrocarbon components  Hydrocarbons can undergo reactions that release a large amount of energy © 2014 Pearson Education, Inc The Chemical Groups Most Important to Life  Functional groups are the components of organic molecules that are most commonly involved in chemical reactions  The number and arrangement of functional groups give each molecule its unique properties © 2014 Pearson Education, Inc  The seven functional groups that are most important in the chemistry of life:  Hydroxyl group  Carbonyl group  Carboxyl group  Amino group  Sulfhydryl group  Phosphate group  Methyl group © 2014 Pearson Education, Inc Figure 3.5 Chemical Group Hydroxyl group ( Compound Name OH) Carbonyl group ( C Examples Alcohol O) Ethanol Ketone Aldehyde Acetone Carboxyl group ( Propanal COOH) Carboxylic acid, or organic acid Acetic acid Amino group ( NH2) Amine Glycine Sulfhydryl group ( SH) Thiol Phosphate group ( OPO32–) Organic phosphate Methyl group ( Glycerol phosphate CH3) Methylated compound © 2014 Pearson Education, Inc Cysteine 5-Methyl cytosine Figure 3.5a Chemical Group Hydroxyl group ( OH) Carbonyl group ( C O) Compound Name Examples Alcohol Ethanol Ketone Aldehyde Acetone Carboxyl group ( COOH) Carboxylic acid, or organic acid Acetic acid Amino group ( NH2) Amine Glycine © 2014 Pearson Education, Inc Propanal Figure 3.5aa Hydroxyl group ( OH) (may be written HO ) Alcohol (The specific name usually ends in -ol.) Ethanol, the alcohol present in alcoholic beverages © 2014 Pearson Education, Inc Figure 3.5ab Carbonyl group ( C O) Ketone if the carbonyl group is within a carbon skeleton Aldehyde if the carbonyl group is at the end of a carbon skeleton Acetone, the simplest ketone © 2014 Pearson Education, Inc Propanal, an aldehyde Figure 3.5ac Carboxyl group ( COOH) Carboxylic acid, or organic acid Acetic acid, which gives vinegar its sour taste © 2014 Pearson Education, Inc Ionized form of COOH (carboxylate ion), found in cells Figure 3.5ad Amino group ( NH2) Amine Glycine, an amino acid (note its carboxyl group) © 2014 Pearson Education, Inc Ionized form of found in cells NH2 Figure 3.5b Chemical Group Sulfhydryl group ( Compound Name SH) Thiol Phosphate group ( Glycerol phosphate CH3) Methylated compound © 2014 Pearson Education, Inc Cysteine OPO32–) Organic phosphate Methyl group ( Examples 5-Methyl cytosine Figure 3.5ba Sulfhydryl group ( SH) Thiol (may be written HS ) Cysteine, a sulfurcontaining amino acid © 2014 Pearson Education, Inc Figure 3.5bb Phosphate group ( OPO32–) Organic phosphate Glycerol phosphate, which takes part in many important chemical reactions in cells © 2014 Pearson Education, Inc Figure 3.5bc Methyl group ( CH3) Methylated compound 5-Methyl cytosine, a component of DNA that has been modified by addition of a methyl group © 2014 Pearson Education, Inc ATP: An Important Source of Energy for Cellular Processes  One organic phosphate molecule, adenosine triphosphate (ATP), is the primary energytransferring molecule in the cell  ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups © 2014 Pearson Education, Inc Figure 3.UN02 Adenosine © 2014 Pearson Education, Inc Figure 3.UN03 Reacts with H2O Adenosine Adenosine ATP © 2014 Pearson Education, Inc Inorganic phosphate ADP Energy Concept 3.2: Macromolecules are polymers, built from monomers  A polymer is a long molecule consisting of many similar building blocks  These small building-block molecules are called monomers  Some molecules that serve as monomers also have other functions of their own © 2014 Pearson Education, Inc The Synthesis and Breakdown of Polymers  Cells make and break down polymers by the same process  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  These processes are facilitated by enzymes, which speed up chemical reactions Animation: Polymers © 2014 Pearson Education, Inc Figure 3.6 (a) Dehydration reaction: synthesizing a polymer Short polymer Longer polymer (b) Hydrolysis: breaking down a polymer © 2014 Pearson Education, Inc Unlinked monomer Figure 3.6a (a) Dehydration reaction: synthesizing a polymer Short polymer Dehydration removes a water molecule, forming a new bond Longer polymer © 2014 Pearson Education, Inc Unlinked monomer Figure 3.6b (b) Hydrolysis: breaking down a polymer Hydrolysis adds a water molecule, breaking a bond © 2014 Pearson Education, Inc 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 variety of polymers can be built from a small set of monomers © 2014 Pearson Education, Inc Concept 3.3: Carbohydrates serve as fuel and building material  Carbohydrates include sugars and the polymers of sugars  The simplest carbohydrates are monosaccharides, or simple sugars  Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks © 2014 Pearson Education, Inc Sugars  Monosaccharides have molecular formulas that are usually multiples of CH2O  Glucose (C6H12O6) is the most common monosaccharide  Monosaccharides are classified by the number of carbons in the carbon skeleton and the placement of the carbonyl group © 2014 Pearson Education, Inc Figure 3.7 Triose: 3-carbon sugar (C3H6O3) Pentose: 5-carbon sugar (C5H10O5) Glyceraldehyde An initial breakdown product of glucose in cells Ribose A component of RNA Hexoses: 6-carbon sugars (C6H12O6) Glucose Fructose Energy sources for organisms © 2014 Pearson Education, Inc Figure 3.7a Triose: 3-carbon sugar (C3H6O3) Glyceraldehyde An initial breakdown product of glucose in cells © 2014 Pearson Education, Inc Figure 3.7b Pentose: 5-carbon sugar (C5H10O5) Ribose A component of RNA © 2014 Pearson Education, Inc Figure 3.7c Hexoses: 6-carbon sugars (C6H12O6) Glucose Fructose Energy sources for organisms © 2014 Pearson Education, Inc  Though often drawn as linear skeletons, in aqueous solutions many sugars form rings  Monosaccharides serve as a major fuel for cells and as raw material for building molecules © 2014 Pearson Education, Inc Figure 3.8 (a) Linear and ring forms (b) Abbreviated ring structure © 2014 Pearson Education, Inc  A disaccharide is formed when a dehydration reaction joins two monosaccharides  This covalent bond is called a glycosidic linkage Animation: Disaccharides © 2014 Pearson Education, Inc Figure 3.9-1 Glucose © 2014 Pearson Education, Inc Fructose Figure 3.9-2 Glucose Fructose 1–2 glycosidic linkage Sucrose © 2014 Pearson Education, Inc Polysaccharides  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 © 2014 Pearson Education, Inc Storage Polysaccharides  Starch, a storage polysaccharide of plants, consists entirely of glucose monomers  Plants store surplus starch as granules  The simplest form of starch is amylose © 2014 Pearson Education, Inc  Glycogen is a storage polysaccharide in animals  Humans and other vertebrates store glycogen mainly in liver and muscle cells Animation: Polysaccharides © 2014 Pearson Education, Inc Figure 3.10 Starch granules in a potato tuber cell Starch (amylose) Glucose monomer Glycogen granules in muscle tissue Cellulose microfibrils in a plant cell wall Cellulose molecules © 2014 Pearson Education, Inc Glycogen Cellulose Hydrogen bonds between —OH groups (not shown) attached to carbons and Figure 3.10a Starch granules in a potato tuber cell Starch (amylose) Glucose monomer © 2014 Pearson Education, Inc Figure 3.10aa Starch granules in a potato tuber cell © 2014 Pearson Education, Inc Figure 3.10b Glycogen granules in muscle tissue © 2014 Pearson Education, Inc Glycogen Figure 3.10ba Glycogen granules in muscle tissue © 2014 Pearson Education, Inc Figure 3.10c Cellulose microfibrils in a plant cell wall Cellulose molecules © 2014 Pearson Education, Inc Cellulose Hydrogen bonds between —OH groups on carbons and Figure 3.10ca Cellulose microfibrils in a plant cell wall © 2014 Pearson Education, Inc Structural Polysaccharides  The polysaccharide cellulose is a major component of the tough wall of plant cells  Like starch and glycogen, cellulose is a polymer of glucose, but the glycosidic linkages in cellulose differ  The difference is based on two ring forms for glucose © 2014 Pearson Education, Inc Figure 3.11 (a)  and  glucose ring structures  Glucose  Glucose (b) Starch: 1–4 linkage of  glucose monomers (c) Cellulose: 1–4 linkage of  glucose monomers © 2014 Pearson Education, Inc Figure 3.11a (a)  and  glucose ring structures  Glucose © 2014 Pearson Education, Inc  Glucose  In starch, the glucose monomers are arranged in the alpha () conformation  Starch (and glycogen) are largely helical  In cellulose, the monomers are arranged in the beta () conformation  Cellulose molecules are relatively straight © 2014 Pearson Education, Inc Figure 3.11b (b) Starch: 1–4 linkage of  glucose monomers © 2014 Pearson Education, Inc Figure 3.11c (c) Cellulose: 1–4 linkage of  glucose monomers © 2014 Pearson Education, Inc  In straight structures (cellulose), H atoms on one strand can form hydrogen bonds with OH groups on other strands  Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants © 2014 Pearson Education, Inc  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 © 2014 Pearson Education, Inc  Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods  Chitin also provides structural support for the cell walls of many fungi © 2014 Pearson Education, Inc Concept 3.4: Lipids are a diverse group of hydrophobic molecules  Lipids not form true polymers  The unifying feature of lipids is having little or no affinity for water  Lipids are hydrophobic because they consist mostly of hydrocarbons, which form nonpolar covalent bonds  The most biologically important lipids are fats, phospholipids, and steroids © 2014 Pearson Education, Inc 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 Animation: Fats © 2014 Pearson Education, Inc Figure 3.12 Fatty acid (in this case, palmitic acid) Glycerol (a) One of three dehydration reactions in the synthesis of a fat Ester linkage (b) Fat molecule (triacylglycerol) © 2014 Pearson Education, Inc Figure 3.12a Fatty acid (in this case, palmitic acid) Glycerol (a) One of three dehydration reactions in the synthesis of a fat © 2014 Pearson Education, Inc  Fats separate from water because water molecules hydrogen-bond to 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 © 2014 Pearson Education, Inc Figure 3.12b Ester linkage (b) Fat molecule (triacylglycerol) © 2014 Pearson Education, Inc  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 © 2014 Pearson Education, Inc Figure 3.13 (a) Saturated fat Structural formula of a saturated fat molecule Space-filling model of stearic acid, a saturated fatty acid © 2014 Pearson Education, Inc (b) Unsaturated fat Structural formula of an unsaturated fat molecule Space-filling model of oleic acid, an unsaturated fatty acid Double bond causes bending Figure 3.13a (a) Saturated fat Structural formula of a saturated fat molecule Space-filling model of stearic acid, a saturated fatty acid © 2014 Pearson Education, Inc Figure 3.13aa © 2014 Pearson Education, Inc Figure 3.13b (b) Unsaturated fat Structural formula of an unsaturated fat molecule Space-filling model of oleic acid, an unsaturated fatty acid © 2014 Pearson Education, Inc Double bond causes bending Figure 3.13ba © 2014 Pearson Education, Inc  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, called unsaturated fats or oils, are liquid at room temperature  Plant fats and fish fats are usually unsaturated © 2014 Pearson Education, Inc  The major function of fats is energy storage  Fat is a compact way for animals to carry their energy stores with them © 2014 Pearson Education, Inc 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  Phospholipids are major constituents of cell membranes © 2014 Pearson Education, Inc Hydrophobic tails Hydrophilic head Figure 3.14 Choline Phosphate Glycerol Fatty acids (a) Structural formula © 2014 Pearson Education, Inc Hydrophilic head Hydrophobic tails (b) Space-filling model (c) Phospholipid symbol (d) Phospholipid bilayer Hydrophobic tails Hydrophilic head Figure 3.14ab Choline Phosphate Glycerol Fatty acids (a) Structural formula © 2014 Pearson Education, Inc (b) Space-filling model  When phospholipids are added to water, they selfassemble into a bilayer, with the hydrophobic tails pointing toward the interior  This feature of phospholipids results in the bilayer arrangement found in cell membranes © 2014 Pearson Education, Inc Figure 3.14cd Hydrophilic head Hydrophobic tails (c) Phospholipid symbol © 2014 Pearson Education, Inc (d) Phospholipid bilayer 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 Video: Cholesterol Space Model Video: Cholesterol Stick Model © 2014 Pearson Education, Inc Figure 3.15 © 2014 Pearson Education, Inc Concept 3.5: 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 defense, storage, transport, cellular communication, movement, and structural support Animation: Contractile Proteins Animation: Defensive Proteins Animation: Enzymes © 2014 Pearson Education, Inc Animation: Gene Regulatory Proteins Animation: Hormonal Proteins Animation: Receptor Proteins Animation: Sensory Proteins Animation: Storage Proteins Animation: Structural Proteins Animation: Transport Proteins © 2014 Pearson Education, Inc Figure 3.16 Enzymatic proteins Defensive proteins Function: Protection against disease Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food Example: Antibodies inactivate and help destroy viruses and bacteria molecules Antibodies Enzyme Bacterium Virus Storage proteins Transport 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 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 Ovalbumin Transport protein Amino acids for embryo Cell membrane Hormonal proteins Receptor 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 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 Insulin secreted High blood sugar Receptor protein Normal blood sugar Signaling molecules Contractile and motor proteins Structural 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 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 Actin Myosin Collagen Muscle tissue © 2014 Pearson Education, Inc 30 m Connective tissue 60 m Figure 3.16a Enzymatic proteins Defensive proteins Function: Selective acceleration of chemical reactions Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules Antibodies Enzyme Virus Bacterium Storage proteins Transport 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 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 Ovalbumin © 2014 Pearson Education, Inc Amino acids for embryo Cell membrane Figure 3.16aa Enzymatic proteins Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules Enzyme © 2014 Pearson Education, Inc Figure 3.16ab Defensive proteins Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria Antibodies Virus © 2014 Pearson Education, Inc Bacterium Figure 3.16ac 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 © 2014 Pearson Education, Inc Amino acids for embryo Figure 3.16aca © 2014 Pearson Education, Inc Figure 3.16ad 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 © 2014 Pearson Education, Inc Figure 3.16b Hormonal proteins Receptor proteins Function: Coordination of an organism’s activities Function: Response of cell to chemical stimuli Example: Insulin, a hormone secreted by the pancreas, causes other tissues to take up glucose, thus regulating blood sugar concentration Example: Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells Receptor protein High blood sugar Insulin secreted Signaling molecules Normal blood sugar 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 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 Myosin Collagen Muscle tissue 30 m © 2014 Pearson Education, Inc Connective tissue 60 m Figure 3.16ba 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 © 2014 Pearson Education, Inc Insulin secreted Normal blood sugar Figure 3.16bb 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 Receptor protein Signaling molecules © 2014 Pearson Education, Inc Figure 3.16bc 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 © 2014 Pearson Education, Inc 30 m Myosin Figure 3.16bca Muscle tissue © 2014 Pearson Education, Inc 30 m Figure 3.16bd 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 © 2014 Pearson Education, Inc Figure 3.16bda Connective tissue 60 m © 2014 Pearson Education, Inc  Life would not be possible without enzymes  Enzymatic proteins act as catalysts, to speed up chemical reactions without being consumed by the reaction © 2014 Pearson Education, Inc  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 © 2014 Pearson Education, Inc Amino Acids  Amino acids are organic molecules with carboxyl and amino groups  Amino acids differ in their properties due to differing side chains, called R groups © 2014 Pearson Education, Inc Figure 3.UN04 Side chain (R group)  carbon Amino group © 2014 Pearson Education, Inc Carboxyl group Figure 3.17 Nonpolar side chains; hydrophobic Side chain (R group) Glycine (Gly or G) Alanine (Ala or A) Phenylalanine (Phe or F) Methionine (Met or M) Leucine (Leu or L) Valine (Val or V) Isoleucine (le or ) Tryptophan (Trp or W) Proline (Pro or P) 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) Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Aspartic acid (Asp or D) © 2014 Pearson Education, Inc Glutamic acid (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) Figure 3.17a Nonpolar side chains; hydrophobic Side chain (R group) Glycine (Gly or G) Methionine (Met or M) © 2014 Pearson Education, Inc Alanine (Ala or A) Valine (Val or V) Phenylalanine (Phe or F) Leucine (Leu or L) Tryptophan (Trp or W) Isoleucine (le or ) Proline (Pro or P) Figure 3.17b Polar side chains; hydrophilic © 2014 Pearson Education, Inc Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) Figure 3.17c Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Aspartic acid Glutamic acid (Asp or D) (Glu or E) © 2014 Pearson Education, Inc Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) Polypeptides  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 (N-terminus) © 2014 Pearson Education, Inc Figure 3.18 Peptide bond New peptide bond forming Side chains Backbone Amino end (N-terminus) © 2014 Pearson Education, Inc Peptide bond Carboxyl end (C-terminus) Figure 3.18a Peptide bond © 2014 Pearson Education, Inc Figure 3.18b Side chains Backbone Amino end (N-terminus) © 2014 Pearson Education, Inc Peptide bond Carboxyl end (C-terminus) Protein Structure and Function  A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape © 2014 Pearson Education, Inc Figure 3.19 Groove Groove (a) A ribbon model © 2014 Pearson Education, Inc (b) A space-filling model Figure 3.19a Groove (a) A ribbon model © 2014 Pearson Education, Inc Figure 3.19b Groove (b) A space-filling model © 2014 Pearson Education, Inc  The sequence of amino acids, determined genetically, leads to a protein’s three-dimensional structure  A protein’s structure determines its function © 2014 Pearson Education, Inc Figure 3.20 Antibody protein © 2014 Pearson Education, Inc Protein from flu virus Four Levels of Protein Structure  Proteins are very diverse, but share three superimposed levels of structure called primary, secondary, and tertiary structure  A fourth level, quaternary structure, arises when a protein consists of more than one polypeptide chain © 2014 Pearson Education, Inc  The 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 from interactions between multiple polypeptide chains © 2014 Pearson Education, Inc Video: Alpha Helix with No Side Chain Video: Alpha Helix with Side Chain Video: Beta Pleated Sheet Video: Beta Pleated Stick Animation: Introduction to Protein Structure Animation: Primary Structure Animation: Secondary Structure Animation: Tertiary Structure Animation: Quaternary Structure © 2014 Pearson Education, Inc Figure 3.21a Primary structure Amino acids 10 Amino end 30 35 15 20 25 45 40 50 Primary structure of transthyretin 65 70 60 55 75 80 90 85 95 115 120 © 2014 Pearson Education, Inc 110 125 105 100 Carboxyl end Figure 3.21aa Primary structure Amino acids 10 Amino end 30 © 2014 Pearson Education, Inc 25 20 15 Figure 3.21b Secondary structure Tertiary structure Quaternary structure Transthyretin polypeptide Transthyretin protein  helix  pleated sheet © 2014 Pearson Education, Inc Figure 3.21ba Secondary structure  helix Hydrogen bond  pleated sheet  strand Hydrogen bond © 2014 Pearson Education, Inc Figure 3.21bb Tertiary structure Transthyretin polypeptide © 2014 Pearson Education, Inc Figure 3.21bc Quaternary structure Transthyretin protein © 2014 Pearson Education, Inc Figure 3.21c © 2014 Pearson Education, Inc Figure 3.21d Hydrogen bond Hydrophobic interactions and van der Waals interactions Disulfide bridge Ionic bond Polypeptide backbone © 2014 Pearson Education, Inc Figure 3.21e Collagen © 2014 Pearson Education, Inc Figure 3.21f Heme Iron  subunit  subunit  subunit  subunit Hemoglobin © 2014 Pearson Education, Inc Sickle-Cell Disease: A Change in Primary Structure  Primary structure is the sequence of amino acids on the polypeptide chain  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 © 2014 Pearson Education, Inc Figure 3.22 Secondary and Tertiary Structures Normal Primary Structure Quaternary Structure Function Normal hemoglobin  subunit  Molecules not associate with one another; each carries oxygen   m Sickle-cell  Exposed hydrophobic region Red Blood Cell Shape Sickle-cell hemoglobin Molecules crystallized into a fiber; capacity to carry oxygen is reduced    subunit © 2014 Pearson Education, Inc   m Figure 3.22a Normal Primary Structure Secondary and Tertiary Structures Quaternary Structure Normal hemoglobin  subunit     © 2014 Pearson Education, Inc Function Molecules not associate with one another; each carries oxygen Figure 3.22aa m © 2014 Pearson Education, Inc Figure 3.22b Sickle-cell Primary Structure © 2014 Pearson Education, Inc Secondary and Tertiary Structures Quaternary Structure Function Exposed hydrophobic region Sickle-cell hemoglobin Molecules crystallized into a fiber; capacity to carry oxygen is reduced    subunit   Figure 3.22ba m © 2014 Pearson Education, Inc 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 © 2014 Pearson Education, Inc Figure 3.23-1 Normal protein © 2014 Pearson Education, Inc Figure 3.23-2 Normal protein © 2014 Pearson Education, Inc Denatured protein Figure 3.23-3 Normal protein © 2014 Pearson Education, Inc Denatured protein Protein Folding in the Cell  It is hard to predict a protein’s structure from its primary structure  Most proteins probably go through several intermediate structures on their way to their final, stable shape  Scientists use X-ray crystallography to determine 3-D protein structure based on diffractions of an X-ray beam by atoms of the crystalized molecule © 2014 Pearson Education, Inc Figure 3.24 Experiment Diffracted X-rays X-ray source X-ray beam Crystal Digital detector X-ray diffraction pattern Results RNA DNA RNA polymerase  © 2014 Pearson Education, Inc Figure 3.24a Experiment Diffracted X-rays X-ray source X-ray beam Crystal © 2014 Pearson Education, Inc Digital detector X-ray diffraction pattern Figure 3.24b Results RNA DNA RNA polymerase  © 2014 Pearson Education, Inc Concept 3.6: 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 © 2014 Pearson Education, Inc 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 © 2014 Pearson Education, Inc Figure 3.25-1 DNA Synthesis of mRNA mRNA NUCLEUS CYTOPLASM © 2014 Pearson Education, Inc Figure 3.25-2 DNA Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA Movement of mRNA into cytoplasm © 2014 Pearson Education, Inc Figure 3.25-3 DNA Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA Movement of mRNA into cytoplasm Ribosome Synthesis of protein Polypeptide © 2014 Pearson Education, Inc Amino acids 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 Animation: DNA and RNA Structure © 2014 Pearson Education, Inc Figure 3.26 5 end Sugar-phosphate backbone (on blue background) Nitrogenous bases Pyrimidines 5C 3C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines 5C 3C Phosphate group Sugar (pentose) Adenine (A) Guanine (G) (b) Nucleotide 3 end Sugars (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) (c) Nucleoside components © 2014 Pearson Education, Inc Ribose (in RNA) Figure 3.26a 5 end Sugar-phosphate backbone (on blue background) 5C 3C Nucleoside Nitrogenous base 5C 3C Phosphate group (b) Nucleotide 3 end (a) Polynucleotide, or nucleic acid © 2014 Pearson Education, Inc Sugar (pentose) Figure 3.26b Nucleoside Nitrogenous base Phosphate group (b) Nucleotide © 2014 Pearson Education, Inc Sugar (pentose) Figure 3.26c Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines Adenine (A) © 2014 Pearson Education, Inc Guanine (G) Figure 3.26d Sugars Deoxyribose (in DNA) © 2014 Pearson Education, Inc Ribose (in RNA)  Each nitrogenous base has one or two rings that include nitrogen atoms  The nitrogenous bases in nucleic acids are called cytosine (C), thymine (T), uracil (U), adenine (A), and guanine (G)  Thymine is found only in DNA, and uracil only in RNA; the rest are found in both DNA and RNA © 2014 Pearson Education, Inc  The sugar in DNA is deoxyribose; in RNA it is ribose  A prime () is used to identify the carbon atoms in the ribose, such as the 2 carbon or 5 carbon  A nucleoside with at least one phosphate attached is a nucleotide © 2014 Pearson Education, Inc Nucleotide Polymers  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 of the next  These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages  The sequence of bases along a DNA or mRNA polymer is unique for each gene © 2014 Pearson Education, Inc 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 © 2014 Pearson Education, Inc  The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)  This is 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 © 2014 Pearson Education, Inc Animation: DNA Double Helix Video: DNA Stick Model Video: DNA Surface Model © 2014 Pearson Education, Inc Figure 3.27 5 3 Sugar-phosphate backbones Hydrogen bonds Base pair joined by hydrogen bonding 3 5 (a) DNA Base pair joined by hydrogen bonding © 2014 Pearson Education, Inc (b) Transfer RNA Figure 3.27a 5 3 Sugar-phosphate backbones Hydrogen bonds 5 Base pair joined by hydrogen bonding (a) DNA 3 © 2014 Pearson Education, Inc Figure 3.27b Sugar-phosphate backbones Hydrogen bonds Base pair joined by hydrogen bonding (b) Transfer RNA © 2014 Pearson Education, Inc 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 © 2014 Pearson Education, Inc Figure 3.UN05 © 2014 Pearson Education, Inc Figure 3.UN06 © 2014 Pearson Education, Inc Figure 3.UN06a © 2014 Pearson Education, Inc Figure 3.UN06b © 2014 Pearson Education, Inc Figure 3.UN07 © 2014 Pearson Education, Inc