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Not happy with your grade? Need help understanding the material? The TLCC Has Free Tutoring LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 5 The Structure and Function of Large Biological Molecules Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc. Overview: The Molecules of Life four classes of large biological molecules: carbohydrates - polymer lipids proteins - polymer nucleic acids - polymer Polymer: made of many small parts each part is a monomer Many biological molecules are polymers © 2011 Pearson Education, Inc. Figure 5.UN02 Overview: The Molecules of Life • Macromolecules = big molecules usually a polymer • Molecular structure and function are linked » Change the structure or shape of a molecule and you will destroy it’s function » “denature” = changing shape of molecule (protein) so that it doesn’t work anymore © 2011 Pearson Education, Inc. The Synthesis and Breakdown of Polymers • dehydration reaction: making bonds (synthesizing a molecule) by taking away water Animation: Polymers © 2011 Pearson Education, Inc. The Synthesis and Breakdown of Polymers • Breaking a polymer apart hydrolysis, a reaction that is essentially the reverse of the dehydration reaction Animation: Polymers © 2011 Pearson Education, Inc. The Diversity of Polymers • Macromolecules – many thousands of kinds HO – Species differences – Individual differences – Cell differences within organism • small set of monomers can make MANY kinds of monomers – A small set of letter make MANY different words © 2011 Pearson Education, Inc. Concept 5.2: Carbohydrates serve as fuel and building material • Carbohydrates - sugars and their polymers • “saccharides” – sugars • monosaccharides © 2011 Pearson Education, Inc. Concept 5.2: Carbohydrates serve as fuel and building material • • • • Carbohydrates - sugars and their polymers “saccharides” – sugars Monosaccharides – 1 sugar Disaccharide – molecule made of 2 sugars • Polysaccharides – long chains of sugar monomers © 2011 Pearson Education, Inc. Sugars • Monosaccharides - CH2O-like formula • Glucose (C6H12O6) is the most common • Monosaccharides are classified by – The number of carbons in the carbon skeleton – The location of the carbonyl group (as aldose or ketose) © 2011 Pearson Education, Inc. • Though often drawn as linear skeletons, in aqueous solutions many sugars form rings • Monosaccharides (especially glucose) serve as a major fuel for cells and as raw material for building molecules © 2011 Pearson Education, Inc. • A disaccharide is formed when a dehydration reaction joins two monosaccharides • This covalent bond is called a glycosidic linkage Animation: Disaccharide © 2011 Pearson Education, Inc. Polysaccharides • Polysaccharides - storage and structural roles • Polysaccharide structure and function which sugar monomers position of glycosidic linkages © 2011 Pearson Education, Inc. Storage Polysaccharides • Starch, a storage polysaccharide of plants, consists entirely of glucose monomers • Plants store surplus starch as granules within chloroplasts and other plastids • The simplest form of starch is amylose © 2011 Pearson Education, Inc. • Glycogen is a storage polysaccharide in animals • Humans and other vertebrates store glycogen mainly in liver and muscle cells © 2011 Pearson Education, Inc. Structural Polysaccharides • The polysaccharide cellulose is a major component of the tough wall of plant cells • Like starch but the glycosidic linkages differ – Why we can’t digest cellulose Animation: Polysaccharides © 2011 Pearson Education, Inc. Figure 5.8 Cellulose microfibrils in a plant cell wall Cell wall Microfibril 10 m 0.5 m Cellulose molecules Glucose monomer • 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. • Chitin: structural polysaccharide of animals – exoskeleton of arthropods – cell walls of many fungi © 2011 Pearson Education, Inc. Concept 5.3: Lipids are a diverse group of hydrophobic molecules • Lipids – NOT A POLYMER • hydrophobic (non-polar covalent bonds) • 3 kinds of lipids in biology – fats, phospholipids, and steroids • Water dissolves things it can make polar bonds with. Has trouble bonding with lipids. © 2011 Pearson Education, Inc. Fats: glycerol + fatty acids • water molecules bonds to water, excluding 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. • Saturated fatty acids • maximum number of hydrogen atoms • no double bonds • Usually solid at room temp Animation: Fats © 2011 Pearson Education, Inc. • Unsaturated fatty acids have one or more double bonds • Each double bond causes a kink in the chain • Usually liquid at room temp Animation: Fats © 2011 Pearson Education, Inc. • Cis vs. Trans © 2011 Pearson Education, Inc. • Essential fatty acids – We can’t make them (must get from food; omega-3) – Used in normal growth – Protect against cardiovascular disease?? • Fats are used for energy storage – Stored in adipose tissue – Also cushion’s organs © 2011 Pearson Education, Inc. Phospholipids • Glycerol + phosphate + two fatty acids Hydrophilic © 2011 Pearson Education, Inc. hydrophobic • The fatty acid tails are hydrophobic • The heads are hydrophilic • Tails point away from water • The major component in membranes © 2011 Pearson Education, Inc. Steroids • Steroids are lipids made of four carbon 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. Steroids • Steroids are lipids made of four carbon rings • Some hormones are steroids • Cholesterol, is also a steroid – Used in animals membranes, but high levels in blood may contribute to cardiovascular disease © 2011 Pearson Education, Inc. Concept 5.4: Proteins include a diversity of structures, resulting in a wide range of functions • Used for EVERYTHING • structural support, storage, transport, cellular communications, movement, and defense against foreign substances © 2011 Pearson Education, Inc. Protein Structure and Function • A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape • If you change the shape, the protein stops working. © 2011 Pearson Education, Inc. • Enzymes: proteins that speed up chemical reactions (acts as a catalyst) • Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life •Shape is crucial to enzyme function •If you denature it, the enzyme stops working Animation: Enzymes © 2011 Pearson Education, Inc. Figure 5.15-a Enzymatic proteins Defensive proteins Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Antibodies Enzyme Virus Bacterium Storage proteins Transport proteins Function: Storage of amino acids 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. 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. Transport protein Ovalbumin Amino acids for embryo Cell membrane Figure 5.15-b 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. High blood sugar Insulin secreted Normal blood sugar Receptor protein 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 100 m Connective tissue 60 m 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 © 2011 Pearson Education, Inc. Amino Acids: protein building blocks • 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. Figure 5.16 Nonpolar side chains; hydrophobic Side chain (R group) Glycine (Gly or G) Alanine (Ala or A) Methionine (Met or M) Isoleucine (Ile or I) Leucine (Leu or L) Valine (Val or V) Phenylalanine (Phe or F) Tryptophan (Trp or W) Proline (Pro or P) Polar side chains; hydrophilic Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Electrically charged side chains; hydrophilic Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) Basic (positively charged) Acidic (negatively charged) Aspartic acid (Asp or D) Glutamic acid (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) Polypeptides: a chain of amino acids • Polypeptides: are unbranched polymers built from the same set of 20 amino acids • A protein has one or more polypeptides © 2011 Pearson Education, Inc. Polypeptide: Amino Acid Polymers • can be short or more than a thousand monomers • Each polypeptide has a carboxyl end (Cterminus) and an amino end (N-terminus) © 2011 Pearson Education, Inc. Four Levels of Protein Structure • 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 when a protein consists of multiple polypeptide chains Animation: Protein Structure Introduction © 2011 Pearson Education, Inc. • A protein’s structure determines its function • The sequence of amino acids determines a protein’s three-dimensional structure • Primary structure, the sequence of amino acids in a protein © 2011 Pearson Education, Inc. • 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. • secondary structure: 3-D shape in local regions of peptide chain • Caused by hydrogen bonds between parts of the polypeptide backbone • Typical secondary structures are a coil called an helix and a folded structure called a pleated sheet Animation: Secondary Protein Structure © 2011 Pearson Education, Inc. • Tertiary structure is determined by interactions between R groups – – – – hydrogen bonds ionic bonds hydrophobic interactions Van der Waals interactions Strong covalent bonds called disulfide bridges may reinforce the protein’s structure Animation: Tertiary Protein Structure © 2011 Pearson Education, Inc. Quaternary structure: if there is more than one polypeptide chains in 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 Animation: Quaternary Protein Structure © 2011 Pearson Education, Inc. Sickle-Cell Disease: A Change in Primary Structure • Changing the primary structure can change the shape and function of a protein • Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin © 2011 Pearson Education, Inc. 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 What Determines Protein Structure? • The chemical environment affects a protein • Changing pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel • Denature: changing a protein away from its natural shape • A denatured protein is biologically inactive • Alzheimer’s • Parkinson’s • Mad cow disease © 2011 Pearson Education, Inc. 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 © 2011 Pearson Education, Inc. Concept 5.5: Nucleic acids store, transmit, and help express hereditary information • a nucleic acid polymer is made of monomers called nucleotides • Genes are instructions written in DNA (many genes on each chromosome) • The DNA sequence of a gene has instructions to make a polypeptide © 2011 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 • Protein synthesis occurs on ribosomes © 2011 Pearson Education, Inc. 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 The Components of Nucleic Acids • Nucleic acids are chains of nucleotides – pentose sugar – phosphate groups – a nitrogenous base • Nucleoside: nucleotide without phosphate © 2011 Pearson Education, Inc. The Components of Nucleic Acids • Nucleic acids are chains of nucleotides – a nitrogenous base – phosphate groups – pentose sugar • Nucleoside: nucleotide without phosphate © 2011 Pearson Education, Inc. • 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. 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 abc…lmnop • sugar-phosphate backbone (side of ladder) with nitrogenous bases as rungs of ladder • The sequence of bases along a DNA or mRNA polymer is the genetic code, the instructions – unique for each gene © 2011 Pearson Education, Inc. The Structures of DNA and RNA Molecules • RNA molecules usually exist as single polypeptide chains (exception: some viruses) • DNA molecules have two chain, – forming a double helix (twisty ladder) • Antiparallel: DNA strands in opposite directions • One DNA molecule includes many genes © 2011 Pearson Education, Inc. complementary base pairing DNA • adenine (A) thymine (T) • guanine (G) cytosine (C) RNA • adenine (A) Uracil (U) • guanine (G) cytosine (C) © 2011 Pearson Education, Inc. 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 DNA and Proteins as Tape Measures of Evolution • DNA sequences: parents offspring • closely related species have more similar DNA than distantly related species • Molecular biology is used to assess evolutionary kinship • Why people are fighting about protista right now © 2011 Pearson Education, Inc. 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. Figure 5. UN12 Not happy with your grade? Need help understanding the material? The TLCC Has Free Tutoring