* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch 5 Biomolc Strc & Fxn
Survey
Document related concepts
Deoxyribozyme wikipedia , lookup
Gene expression wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Interactome wikipedia , lookup
Western blot wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Genetic code wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Point mutation wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Metalloprotein wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Biosynthesis wikipedia , lookup
Protein structure prediction wikipedia , lookup
Transcript
Chapter 5 The Structure and Function of Large Biological Molecules PowerPoint® Lecture Presentations for Biology 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 Overview: The Molecules of Life • Living things are made of four classes of large biomolecules: carbohydrates, lipids, proteins, and nucleic acids • Macromolecules-large molecules made of small organic molecules covalently bonded together • Molecular structure and function are inseparable (form follows function) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 5.1: Macromolecules are polymers, built from monomers • Polymer- long molecule consisting of many similar building blocks • Monomers- small building-block molecules • Three out of four classes of organic molecules are polymers. They are: – Carbohydrates – Proteins – Nucleic acids Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Synthesis and Breakdown of Polymers • Condensation reaction (also called dehydration reaction)- when two monomers bond together by losing a water molecule • Hydrolysis- breaks down polymers to monomers by adding a water molecule- (reverse process) • Enzymes- macromolecules that speed up chemical reactions Animation: Polymers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-2 HO 1 2 3 H Short polymer HO Unlinked monomer Dehydration removes a water molecule, forming a new bond HO 2 1 H 3 H2O 4 H Longer polymer (a) Dehydration reaction in the synthesis of a polymer HO 1 2 3 4 Hydrolysis adds a water molecule, breaking a bond HO 1 2 3 (b) Hydrolysis of a polymer H H H2O HO H The Diversity of Polymers • A variety of polymers can be built from a small set of monomers • So cells have thousands of different macromolecules • Macromolecules vary among cells in an organism, vary more within a species, and even more between species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 5.2: Carbohydrates serve as fuel and building material • Carbohydrates include sugars and polymers of sugars • Monosaccharides, or single sugars are the simplest carbohydrates • Polysaccharides are polymers composed of many sugar building blocks or carbohydrate macromolecules, Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sugars • Monosaccharide molecular formulas are usually multiples of CH2O • Glucose (C6H12O6) is the most common one • Monosaccharides are classified by – The location of the carbonyl group (as aldose or ketose) – The number of carbons in the carbon skeleton Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-3 Trioses (C3H6O3) Pentoses (C5H10O5) Hexoses (C6H12O6) Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Fructose • Aldose- has a carbonyl at the end • Ketose- has a carbonyl in the middle • Though drawn as linear skeletons, in aqueous solutions many sugars form rings • Monosaccharides are a major fuel for cells and a raw material for building molecules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-4 (a) Linear and ring forms (b) Abbreviated ring structure • Disaccharide- formed when a dehydration reaction joins two monosaccharides • Glycosidic linkage- a covalent bond between two monosaccharides • The structure and function of a polysaccharide are determined by the sugar monomers in it and the positions of glycosidic linkages • Polysaccharides, the polymers of sugars, have storage and structural roles Animation: Disaccharides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-5 1–4 glycosidic linkage Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose 1–2 glycosidic linkage Glucose Fructose (b) Dehydration reaction in the synthesis of sucrose Sucrose Storage Polysaccharides • Starch, a storage polysaccharide of plants, made of glucose monomers only • Plants store surplus starch as granules within chloroplasts and other plastids • Glycogen is a storage polysaccharide in animals • Humans and other vertebrates store glycogen mainly in liver and muscle cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-6 Chloroplast Mitochondria Glycogen granules Starch 0.5 µm 1 µm Glycogen Amylose Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide Structural Polysaccharides • Cellulose is a structural polysaccharide, a major component of tough plant cell walls • Cellulose also is a polymer of glucose, but the glycosidic linkages are different • The difference is based on two ring forms for glucose: alpha () and beta () Animation: Polysaccharides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-7 (a) α and β glucose ring structures α Glucose (b) Starch: 1–4 linkage of α glucose monomers β Glucose (b) Cellulose: 1–4 linkage of β glucose monomers • Polymers with glucose are helical • Polymers with glucose are straight • In straight, , structures, H atoms on one strand bond with OH groups on other strands • So, parallel cellulose molecules held together group into microfibrils, which form strong building materials for plants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-8 Cell walls Cellulose microfibrils in a plant cell wall Microfibril 10 µm 0.5 µm Cellulose molecules b Glucose monomer • Enzymes that digest starch by hydrolyzing linkages can’t hydrolyze linkages in cellulose • So, cellulose in human food passes through the digestive tract as insoluble fiber • Many herbivores, like cows, have symbiotic relationships with microbes that use enzymes to digest cellulose Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Chitin is a structural polysaccharide found in the exoskeleton of arthropods and the cell walls of fungi (a) The structure of the chitin monomer (b) Chitin forms the exoskeleton of arthropods Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings (c) Chitin used as strong flexible surgical thread Concept 5.3: Lipids are a diverse group of hydrophobic molecules • Lipids- the only large biomolecule class that can’t form polymers • ALL lipids have little or no affinity for water • Lipids are made of hydrocarbons which form nonpolar covalent bonds, making lipids hydrophobic • The most important lipids are fats, phospholipids, and steroids Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fats • Fats- made from glycerol and fatty acids • Glycerol- three-carbon alcohol with a hydroxyl group attached to each carbon • Fatty acid- carboxyl group attached to a long carbon skeleton • Fats separate from water because water molecules form hydrogen bonds & exclude fats • Fats are three fatty acids joined to glycerol by an ester linkage, making a triacylglycerol or triglyceride Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-11 Fatty acid (palmitic acid) Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage (b) Fat molecule (triacylglycerol) • An ester linkage is a Carbon-to-Oxygen-toCarbon series of covalent bonds • Fatty acids vary in length (number of carbons) and 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-12a Structural formula of a saturated fat molecule Stearic acid, a saturated fatty acid (a) Saturated fat Fig. 5-12b Structural formula of an unsaturated fat molecule Oleic acid, an unsaturated fatty acid (b) Unsaturated fat cis double bond causes bending • Saturated fats- made from saturated fatty acids; solid at room temperature – Most animal fats are saturated • Unsaturated fats (oils)- made from unsaturated fatty acids; liquid at room temperature – Plant fats and fish fats are usually unsaturated • Diets rich in saturated fats may cause cardiovascular disease through plaque deposits Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Hydrogenation adds hydrogen to unsaturated fats – changes unsaturated fats to saturated fats – makes unsaturated fats with trans double bonds • These trans fats may contribute more than saturated fats to cardiovascular disease!! • Humans & mammals store fat in adipose cells • The major function of fats is energy storage • Adipose tissue also cushions vital organs and insulates the body Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phospholipids • Phospholipid- two fatty acids and a phosphate group attached to glycerol • The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hydrophobic tails Hydrophilic head Fig. 5-13 (a) Structural formula Choline Phosphate Glycerol Fatty acids Hydrophilic head Hydrophobic tails (b) Space-filling model (c) Phospholipid symbol • Phospholipids are the major component of all cell membranes – Added to water, they self-assemble into a bilayer, with hydrophobic tails pointing inward. – Thus the structure results in the bilayer arrangement seen in cell membranes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-14 Hydrophilic head Hydrophobic tail WATER WATER Steroids • Steroids- lipids having a carbon skeleton consisting of four fused rings • Cholesterol- important steroid component in animal cell membranes; stabilizes membranes • Cholesterol is essential in animals, but high levels in the blood may contribute to cardiovascular disease Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-15 Notice the similarity in ring structure between cholesterol and the hormones estradiol & testosterone. Concept 5.4: Proteins have many structures, resulting in a wide range of functions • Proteins are more than 50% of the dry mass of most cells • Protein functions include – – – – – – structural support storage transport cellular communications movement defense against foreign substances • A protein consists of one or more polypeptides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Animation: Structural Proteins Animation: Storage Proteins Animation: Transport Proteins Animation: Receptor Proteins Animation: Contractile Proteins Animation: Defensive Proteins Animation: Hormonal Proteins Animation: Sensory Proteins Animation: Gene Regulatory Proteins Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Polypeptides are polymers built from a set of 20 amino acids. • Enzymes are a type of protein (polypeptide) 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-16 Substrate (sucrose) Glucose OH Fructose HO Enzyme (sucrase) H2O Amino Acid Monomers • Amino acids- organic molecules with carboxyl and amino groups • Their properties differ due to differing side chains, called R groups • There are 20 amino acids Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-UN1 α carbon Amino group Carboxyl group Fig. 5-17a Nonpolar 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) Fig. 5-17b Polar Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Asparagine Glutamine (Asn or N) (Gln or Q) Fig. 5-17c Electrically charged Acidic Aspartic acid Glutamic acid (Glu or E) (Asp or D) Basic Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) Amino Acid Polymers • Amino acids are linked by peptide bonds to make polypeptides • Polypeptide- polymer of amino acids, range in length from few to over a thousand monomers • Each has a unique linear amino acid sequence • All proteins are polypeptides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-18 Peptide bond (a) Side chains Peptide bond Backbone (b) Amino end (N-terminus) Carboxyl end (C-terminus) Protein Structure and Function • Functional proteins are one or more polypeptides twisted, folded, and coiled into a unique shape • A protein’s amino acid sequence determines its three-dimensional structure • The structure determines its function (form follows function) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-19 Groove Groove (a) A ribbon model of lysozyme (b) A space-filling model of lysozyme Fig. 5-20 Antibody protein Protein from flu virus Four Levels of Protein Structure • Primary- the unique sequence of amino acids • Secondary- coils & folds in polypeptide chain • Tertiary- due to interactions among various side chains (R groups) • Quaternary- seen when a protein is made of multiple polypeptide chains • Primary structure is like the order of letters in a long word and is due to inherited genetic information Animation: Protein Structure Introduction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Animation: Primary Protein Structure Fig. 5-21a Primary Structure 1 +H 5 3N Amino end 10 Amino acid subunits 15 20 25 • Secondary structure coils and folds result from hydrogen bonds between repeating parts of the polypeptide backbone Examples: – helix- a coil – pleated sheet- a folded structure Animation: Secondary Protein Structure Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-21c Secondary Structure β pleated sheet Examples of amino acid subunits α helix • Tertiary structure is due to interactions between R groups (not backbone constituents) – R group interactions include hydrogen and ionic bonds, also hydrophobic and van der Waals interactions – Disulfide bridges are strong covalent bonds that reinforce the protein’s structure • Quaternary structure- two or more polypeptide chains form one macromolecule Animation: Tertiary Protein Structure Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-21e Tertiary Structure Quaternary Structure Coils or sheets due to Rgroup interactions Protein subunits of an enzyme held together by hydrogen bonds, disulfide,Van der Waals forces, etc. Fig. 5-21f Hydrophobic interactions and van der Waals interactions Polypeptide backbone Hydrogen bond Disulfide bridge Ionic bond Fig. 5-21g Polypeptide chain α Chains Iron Heme β Chains Hemoglobin Collagen Collagen- fibrous protein made of three polypeptides coiled like a rope Hemoglobin- globular protein made of four polypeptides: two alpha and two beta chains Animation: Quaternary Protein Structure Sickle-Cell Disease: A Change in Primary Structure • Small changes in primary structure can affect protein structure and ability to function • Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin 10 µm 10 µm Normal red blood cells are full of individual hemoglobin molecules, each carrying oxygen. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fibers of abnormal hemoglobin deform red blood cell into sickle shape. Normal hemoglobin Primary structure Sickle-cell hemoglobin Primary structure Val His Leu Thr Pro Glu Glu 1 2 3 Secondary and tertiary structures 4 5 6 7 subunit Secondary and tertiary structures Val His Leu Thr Pro Val Glu 1 2 3 Exposed hydrophobic region Quaternary structure Normal hemoglobin (top view) Quaternary structure Sickle-cell hemoglobin Function Molecules do not associate with one another; each carries oxygen. Function Molecules interact with one another and crystallize into a fiber; capacity to carry oxygen is greatly reduced. 10 µm Red blood cell shape Normal red blood cells are full of individual hemoglobin moledules, each carrying oxygen. 4 5 6 7 subunit 10 µm Red blood cell shape Fig. 5-22 Fibers of abnormal hemoglobin deform red blood cell into sickle shape. What Determines Protein Structure? • Denaturation- loss of a protein’s native structure – Changes in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel – A denatured protein is biologically inactive Denaturation Normal protein Denatured protein Renaturation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-23 Protein Folding in the Cell • Chaperonins are protein molecules that assist the proper folding of other proteins Correctly folded protein Cap Polypeptide Hollow cylinder Chaperonin (fully assembled) Fig. 5-24 Steps of Chaperonin Action: 1 An unfolded poly-peptide enters the cylinder from one end. 2 The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide. 3 The cap comes off, and the properly folded protein Is released. Determining Shapes in the Cell • To determine protein structure, scientists use: – X-ray crystallography – nuclear magnetic resonance (NMR) spectroscopy, (doesn’t require protein crystallization) – Bioinformatics- uses computer programs to predict structure from amino acid sequences Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-25 EXPERIMENT Diffracted X-rays X-ray source X-ray beam Crystal Digital detector X-ray diffraction pattern RESULTS RNA polymerase II DNA RNA Concept 5.5: Nucleic acids store and transmit hereditary information • Genes program the amino acid sequence of a polypeptide • Genes are made of DNA, a nucleic acid • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-26-3 DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm via nuclear pore Ribosome 3 Synthesis of protein Polypeptide Amino acids The Structure of Nucleic Acids • Nucleic acids- polymers called polynucleotides • Polynucleotides are made of monomers called nucleotides which consist of: – nitrogenous base – pentose sugar – a phosphate group • Nucleoside- a nucleotide lacking the phosphate group (base & sugar, only) • Nucleoside = nitrogenous base + sugar Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-27 5 end Nitrogenous bases Pyrimidines 5 C 3 C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines Phosphate group 5 C Sugar (pentose) Adenine (A) Guanine (G) (b) Nucleotide 3 C Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars Nucleotide Monomers • Nucleotide = nucleoside + phosphate group • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nucleotide Polymers • Nucleotide polymers link up to make polynucleotides • Nucleotides join by covalent bonds between the –OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon of the next • The links make a backbone of sugar-phosphate units with nitrogen bases as appendages • The sequence of bases on DNA or mRNA polymers is unique to each gene Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The DNA Double Helix • A DNA molecule has two polynucleotide strands spiraling around each other, making a double helix • The backbones of the two strands run in opposite 5 → 3 directions from each other, or antiparallel • One DNA molecule has many genes • Nitrogen bases in DNA pair up forming hydrogen bonds: – adenine (A) with thymine (T) – guanine (G) with cytosine (C) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 5-28 5' end 3' end Sugar-phosphate backbones Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand 3' end 5' end New strands 5' end 3' end 5' end 3' end DNA and Proteins as Tape Measures of Evolution • DNA nucleotide sequences are passed from parents to offspring • Two closely related species have more similar DNA than more distantly related species • Molecular biology can be used to assess evolutionary kinship Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Emergent Properties in the Chemistry of Life • Higher levels of organization cause the emergence of new properties • Organization is the key to the chemistry of life • Form follows function- as seen in the shapes of the macromolecules seen here Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings