1 The Structure and Function of Large Biological MoleculesChapter 5 The Structure and Function of Large Biological Molecules

2 Figure 5.1 Figure 5.1 Why do scientists study the structures of macromolecules?

3 Concept 5.1: Macromolecules are polymers, built from monomersThree of the four classes of life’s organic molecules are polymers Carbohydrates Proteins Nucleic acids © 2011 Pearson Education, Inc.

4 The Synthesis and Breakdown of Polymersdehydration reaction hydrolysis Animation: Polymers © 2011 Pearson Education, Inc.

5 (a) Dehydration reaction: synthesizing a polymerFigure 5.2a (a) Dehydration reaction: synthesizing a polymer 1 2 3 Short polymer Unlinked monomer Dehydration removes a water molecule, forming a new bond. Figure 5.2 The synthesis and breakdown of polymers. 1 2 3 4 Longer polymer

6 (b) Hydrolysis: breaking down a polymerFigure 5.2b (b) Hydrolysis: breaking down a polymer 1 2 3 4 Hydrolysis adds a water molecule, breaking a bond. Figure 5.2 The synthesis and breakdown of polymers. 1 2 3

7 Concept 5.2: Carbohydrates serve as fuel and building materialMonosaccharides - or single sugars Polysaccharides - polymers composed of many sugar building blocks © 2011 Pearson Education, Inc.

8 Sugars Monosaccharides – 1:2:1 ratio CHO classified byThe location of the carbonyl group (as aldose or ketose) The number of carbons in the carbon skeleton © 2011 Pearson Education, Inc.

9 Figure 5.3 The structure and classification of some monosaccharides.Aldoses (Aldehyde Sugars) Ketoses (Ketone Sugars) Trioses: 3-carbon sugars (C3H6O3) Glyceraldehyde Dihydroxyacetone Pentoses: 5-carbon sugars (C5H10O5) Ribose Ribulose Hexoses: 6-carbon sugars (C6H12O6) Figure 5.3 The structure and classification of some monosaccharides. Glucose Galactose Fructose

10 Aldose (Aldehyde Sugar) Ketose (Ketone Sugar)Figure 5.3c Aldose (Aldehyde Sugar) Ketose (Ketone Sugar) Hexoses: 6-carbon sugars (C6H12O6) Figure 5.3 The structure and classification of some monosaccharides. Glucose Galactose Fructose

11 (a) Linear and ring formsFigure 5.4 1 6 6 2 5 5 3 4 1 4 1 4 2 2 5 3 3 6 (a) Linear and ring forms Figure 5.4 Linear and ring forms of glucose. 6 5 4 1 3 2 (b) Abbreviated ring structure

12 (a) Dehydration reaction in the synthesis of maltoseFigure 5.5 1–4 glycosidic linkage 1 4 Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose 1–2 glycosidic linkage 1 2 Figure 5.5 Examples of disaccharide synthesis. Glucose Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose

13 Polysaccharides storage structural roles Polysaccharides© 2011 Pearson Education, Inc.

14 Storage PolysaccharidesStarch - glucose monomers stores surplus starch as granules within chloroplasts and other plastids simplest form of starch is amylose © 2011 Pearson Education, Inc.

15 (a) Starch: a plant polysaccharideFigure 5.6 Chloroplast Starch granules Amylopectin Amylose (a) Starch: a plant polysaccharide 1 m Mitochondria Glycogen granules Figure 5.6 Storage polysaccharides of plants and animals. Glycogen (b) Glycogen: an animal polysaccharide 0.5 m

16 Glycogen is a storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells © 2011 Pearson Education, Inc.

17 Structural Polysaccharidescellulose is a major component of the tough wall of plant cells polymer of glucose with different glycosidic linkages differ The difference is based on two ring forms for glucose: alpha () and beta () Animation: Polysaccharides © 2011 Pearson Education, Inc.

18 (a)  and  glucose ring structuresFigure 5.7 (a)  and  glucose ring structures 4 1 4 1  Glucose  Glucose 1 4 1 4 Figure 5.7 Starch and cellulose structures. (b) Starch: 1–4 linkage of  glucose monomers (c) Cellulose: 1–4 linkage of  glucose monomers

19 Cellulose microfibrils in a plant cell wallFigure 5.8 Cellulose microfibrils in a plant cell wall Cell wall Microfibril 10 m 0.5 m Figure 5.8 The arrangement of cellulose in plant cell walls. Cellulose molecules  Glucose monomer

20 Some microbes use enzymes to digest cellulose 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.

22 Concept 5.3: Lipids are a diverse group of hydrophobic moleculesdo not form polymers hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds important lipids are fats, phospholipids, and steroids © 2011 Pearson Education, Inc.

23 Fatty acid (in this case, palmitic acid)Figure 5.10 Fatty acid (in this case, palmitic acid) Glycerol (a) One of three dehydration reactions in the synthesis of a fat Ester linkage Figure 5.10 The synthesis and structure of a fat, or triacylglycerol. (b) Fat molecule (triacylglycerol)

24 Structural formula of a saturated fat moleculeFigure 5.11 (b) Unsaturated fat (a) Saturated fat Structural formula of a saturated fat molecule Structural formula of an unsaturated fat molecule Space-filling model of stearic acid, a saturated fatty acid Figure 5.11 Saturated and unsaturated fats and fatty acids. Space-filling model of oleic acid, an unsaturated fatty acid Cis double bond causes bending.

25 Hydrogenation trans fats Energy storage Omega-3 Adipose tissue© 2011 Pearson Education, Inc.

26 (a) Structural formula (b) Space-filling model (c) Phospholipid symbolFigure 5.12 Choline Hydrophilic head Phosphate Glycerol Fatty acids Hydrophobic tails Hydrophilic head Figure 5.12 The structure of a phospholipid. Hydrophobic tails (a) Structural formula (b) Space-filling model (c) Phospholipid symbol

27 (a) Structural formula (b) Space-filling modelFigure 5.12a Choline Hydrophilic head Phosphate Glycerol Fatty acids Hydrophobic tails Figure 5.12 The structure of a phospholipid. (a) Structural formula (b) Space-filling model

28 Hydrophilic head WATER Hydrophobic tail WATER Figure 5.13Figure 5.13 Bilayer structure formed by self-assembly of phospholipids in an aqueous environment. Hydrophobic tail WATER

29 Figure 5.14 Figure 5.14 Cholesterol, a steroid.

30 Concept 5.4: Proteins 50% of the dry mass of most cells functionsstructural support Storage Transport cellular communications Movement defense against foreign substances © 2011 Pearson Education, Inc.

31 Enzymatic proteins EnzymeFigure 5.15a Enzymatic proteins Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Enzyme Figure 5.15 An overview of protein functions.

32 Storage proteins Ovalbumin Amino acids for embryoFigure 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. Figure 5.15 An overview of protein functions. Ovalbumin Amino acids for embryo

33 Hormonal proteins Insulin secreted High blood sugar Normal blood sugarFigure 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 Figure 5.15 An overview of protein functions. Insulin secreted High blood sugar Normal blood sugar

34 Contractile and motor proteinsFigure 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 Myosin Figure 5.15 An overview of protein functions. Muscle tissue 100 m

35 Defensive proteins Antibodies Virus BacteriumFigure 5.15e Defensive proteins Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Antibodies Figure 5.15 An overview of protein functions. Virus Bacterium

36 Transport proteins Transport protein Cell membraneFigure 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 Figure 5.15 An overview of protein functions. Cell membrane

37 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. Receptor protein Figure 5.15 An overview of protein functions. Signaling molecules

38 Structural proteins Collagen Connective tissue 60 m Function: SupportFigure 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 Figure 5.15 An overview of protein functions. Connective tissue 60 m

39 carboxyl and amino groups Amino Acid Monomers carboxyl and amino groups differ in their properties due to differing side chains, called R groups © 2011 Pearson Education, Inc.

40 Side chain (R group)  carbon Amino group Carboxyl group Figure 5.UN01Figure 5.UN01 In-text figure, p. 78 Amino group Carboxyl group

41 Figure 5.16 The 20 amino acids of proteins.Nonpolar side chains; hydrophobic Side chain (R group) Glycine (Gly or G) Alanine (Ala or A) Valine (Val or V) Leucine (Leu or L) Isoleucine (Ile or I) Methionine (Met or M) 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) Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) Figure 5.16 The 20 amino acids of proteins. Electrically charged side chains; hydrophilic 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)

42 Amino end (N-terminus) Carboxyl end (C-terminus)Figure 5.17 Peptide bond New peptide bond forming Side chains Figure 5.17 Making a polypeptide chain. Back- bone Peptide bond Amino end (N-terminus) Carboxyl end (C-terminus)

43 Four Levels of Protein Structureprimary structure Secondary structure Tertiary Quaternary Animation: Protein Structure Introduction © 2011 Pearson Education, Inc.

44 Primary structure of transthyretinFigure 5.20a Primary structure Amino acids Amino end Primary structure of transthyretin Figure 5.20 Exploring: Levels of Protein Structure Carboxyl end

45 Transthyretin proteinFigure 5.20b Secondary structure Tertiary structure Quaternary structure  helix Hydrogen bond  pleated sheet  strand Figure 5.20 Exploring: Levels of Protein Structure Transthyretin protein Hydrogen bond Transthyretin polypeptide

46  strand, shown as a flat arrow pointing toward the carboxyl endFigure 5.20c Secondary structure  helix Hydrogen bond  pleated sheet  strand, shown as a flat arrow pointing toward the carboxyl end Figure 5.20 Exploring: Levels of Protein Structure Hydrogen bond

47 Tertiary structure is determined by interactions between R groups hydrogen bonds ionic bonds hydrophobic interactions van der Waals interactions disulfide bridges may reinforce the protein’s structure Animation: Tertiary Protein Structure © 2011 Pearson Education, Inc.

48 Disulfide bridge Hydrogen bondFigure 5.20f Hydrogen bond Hydrophobic interactions and van der Waals interactions Disulfide bridge Ionic bond Figure 5.20 Exploring: Levels of Protein Structure Polypeptide backbone

49 Transthyretin protein (four identical polypeptides)Figure 5.20g Quaternary structure Transthyretin protein (four identical polypeptides) Figure 5.20 Exploring: Levels of Protein Structure

50 Figure 5.20h Collagen Figure 5.20 Exploring: Levels of Protein Structure

51 Heme Iron  subunit  subunit  subunit  subunit HemoglobinFigure 5.20i Heme Iron  subunit  subunit  subunit Figure 5.20 Exploring: Levels of Protein Structure  subunit Hemoglobin

52 What Determines Protein Structure?This loss of a protein’s native structure is called denaturation A denatured protein is biologically inactive © 2011 Pearson Education, Inc.

53 n a tu r a t De i on Normal protein Re on Denatured protein n a t u rFigure 5.22 n a tu r a t De i on Figure 5.22 Denaturation and renaturation of a protein. Normal protein Re on Denatured protein n a t u r a t i

54 Correctly folded proteinFigure 5.23b Correctly folded protein Polypeptide Steps of Chaperonin Action: Figure 5.23 A chaperonin in action. 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. 1 An unfolded poly- peptide enters the cylinder from one end.

55 DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM Figure 5.25-1Figure 5.25 DNA → RNA → protein.

56 Movement of mRNA into cytoplasmFigure DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Figure 5.25 DNA → RNA → protein.

57 Movement of mRNA into cytoplasm RibosomeFigure DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Ribosome Figure 5.25 DNA → RNA → protein. 3 Synthesis of protein Amino acids Polypeptide

58 Figure 5.26 Components of nucleic acids.Sugar-phosphate backbone 5 end Nitrogenous bases Pyrimidines 5C 3C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines 5C 1C Phosphate group 3C 5C Sugar (pentose) Adenine (A) Guanine (G) 3C (b) Nucleotide Figure 5.26 Components of nucleic acids. Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components

59 Base pair joined by hydrogen bondingFigure 5.27 5 3 Sugar-phosphate backbones Hydrogen bonds Base pair joined by hydrogen bonding Figure 5.27 The structures of DNA and tRNA molecules. Base pair joined by hydrogen bonding 3 5 (a) DNA (b) Transfer RNA

60 DNA and Proteins as Tape Measures of EvolutionThe 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.