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Ch. 5 The Structure and Function of Macromolecules

Ch. 5 The Structure and Function of Macromolecules. The 4 Macromolecules. Carboyhydrates Lipids Proteins Nucleic acids may consist of thousands of covalently bonded atoms. Similarities:. chainlike molecules ( polymers )

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Ch. 5 The Structure and Function of Macromolecules

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  1. Ch. 5 The Structure and Function of Macromolecules

  2. The 4 Macromolecules • Carboyhydrates • Lipids • Proteins • Nucleic acids • may consist of thousands of covalently bonded atoms

  3. Similarities: • chainlike molecules (polymers) • polymer -a long molecule with similar or identical building blocks linked by covalent bonds. • small units – monomers • All contain C, H, O

  4. How are polymers made and broken down? • hydrolysis • dehydration synthesis reaction • Both involve water

  5. 1 HO H 3 2 H HO Unlinked monomer Short polymer Dehydration removes a water molecule, forming a new bond H2O 1 2 3 4 HO H Longer polymer (a) Dehydration reaction in the synthesis of a polymer 1 2 3 HO 4 H Hydrolysis adds a watermolecule, breaking a bond H2O 1 3 H HO 2 HO H (b) Hydrolysis of a polymer – ex. digestion Figure 5.2 The synthesis and breakdown of polymers

  6. Carbohydrates Sugars Cellulose Chitin

  7. Carbohydrates include sugars and their polymers. • Monosaccharides – simple sugars • CH20 • Sugars end in -ose • Nutrient for cells (glucose) • fuel • Disaccharides (double sugars) - two monosaccharides join by dehydration synthesis - a condensation reaction • Polysaccharides - polymers of many monosaccharides. • Function as storage and building materials

  8. Triose sugars(C3H6O3) Pentose sugars(C5H10O5) Hexose sugars(C6H12O6) H H H H O O O O C C C C H C OH H C OH H C OH H C OH H C OH HO C H H C OH HO C H Aldoses H H C OH H C OH HO C H H C OH H C OH H C OH Glyceraldehyde H C OH H C OH H Ribose H H Glucose Galactose H H H H C OH H C OH H C OH C O C O C O HO C H H C OH H C OH H C OH H C OH Ketoses H H C OH Dihydroxyacetone H C OH H C OH H Ribulose H Fructose Figure 5.3 Monosaccharides Intermediate in photosynethesis Sunless tanning product

  9. Carbonyl O H hydroxyl 1 C 6CH2OH 6CH2OH 2 CH2OH H C OH H 5C O 5 C O 6 3 H O H H H H H 5 HO C H HOH HOH H 4 4C 1 C 1C 4C 4 1 OH H H H C OH O HO OH 3 2 OH OH 5 OH 2 C C 3 C 2C 3 OH H C H OH 6 H H OH OH H C OH H (a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5. Figure 5.4 Linear and ring forms of glucose (b) Abbreviated ring structure. Each corner represents a carbon. The ring’s thicker edge indicates that you are looking at the ring edge-on; the components attached to the ring lie above or below the plane of the ring.

  10. Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide. (a) CH2OH CH2OH CH2OH CH2OH O O O O 1–4glycosidiclinkage H H H H H H H H HOH HOH HOH HOH 4 1 H H H H OH OH O H OH HO HO OH O H H H H OH OH OH OH H2O Glucose Maltose Glucose CH2OH CH2OH CH2OH CH2OH O O O O 1–2glycosidiclinkage H H H H H H HOH HOH 2 1 Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose.Notice that fructose,though a hexose like glucose, forms a five-sided ring. H H HO H HO H (b) OH H O O HO CH2OH HO CH2OH H OH H H OH H OH OH H2O Glucose Sucrose Fructose Figure 5.5 How are monomers added to carbs?

  11. What are polysaccharides used for? • Energy storage • Starch – plants • Glycogen – animals • Structural support • Cellulose • Chitin

  12. Starch Chloroplast Mitochondria Giycogen granules 0.5 m 1 m Amylose Amylopectin Glycogen (b) Glycogen: an animal polysaccharide (a) Starch: a plant polysaccharide Figure 5.6 Storage polysaccharides of plants and animals Plant storage Animal storage • Both are polymers consisting entirely of glucose monomers

  13. H O C CH2OH CH2OH OH H C H O O OH H H H H HO C H 4 4 1 OH H OH H HO OH H HO H C OH H OH OH H C OH H  glucose C  glucose H OH (a)  and  glucose ring structures CH2OH CH2OH CH2OH CH2OH O O O O 1 4 4 4 1 1 1 OH OH OH OH O O O O HO OH OH OH OH (b) Starch: 1–4 linkage of  glucose monomers OH OH CH2OH CH2OH O O O O OH OH OH OH 4 O 1 HO OH O O CH2OH CH2OH OH OH (c) Cellulose: 1–4 linkage of  glucose monomers Figure 5.7 Starch and cellulose structures Differ in OH placement Whether it is above or below the plane of the ring Isomers with different “glycosidic linkages” Form helical structures Form straight structures

  14. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. Cellulose microfibrils in a plant cell wall Microfibril Cell walls  0.5 m Plant cells OH OH CH2OH CH2OH O O O O OH OH OH OH O O O O O Cellulose molecules CH2OH OH CH2OH OH CH2OH OH CH2OH OH O O O O OH OH OH OH O O O Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. O O CH2OH OH CH2OH OH CH2OH CH2OH OH OH O O O O OH OH OH OH O O O A cellulose molecule is an unbranched  glucose polymer. O O CH2OH OH CH2OH OH • Glucose monomer Figure 5.8 The arrangement of cellulose in plant cell walls -a major component of the tough walls that enclose plant cells Most abundant organic compound on earth!

  15. CH2OH O OH H H OH H OH H H NH O C CH3 (a) The structure of the chitin monomer. (b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging in adult form. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. Figure 5.10 Chitin, a structural polysaccharide Nitrogen appendage; different from cellulose Found in the cell walls of many fungi

  16. Review Questions • The building blocks of carbohydrates are? Function in? • A glycosidic linkage is between what? • What is the polysaccharide of plants called? Of animals? • How does a cellulose molecule differ from a starch? Differ from a chitin?

  17. Lipids Fats Oils Waxes Phospholipids Steroids Smallest unit – fatty acid + glycerol

  18. Lipids • do not form polymers. • little or no affinity for water. • mostly of hydrocarbons • form nonpolar covalent bonds. • major function - energy storage .

  19. H H H H H H H H O H H H H H H H H C C C C C C C H C H O H C C C C C C C C C HO H H H H H H H H H H H H H H H H C OH Fatty acid (palmitic acid) H C OH H Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage O H H H H H H H H H H H H H H H H H H O C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H O H H H H H H H H H H H H H H H O C C C H C C C C C H C C C C C C C C C H H H H H H H H H H H H H H H O H H H H H H H H H H H H H H H H H O C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H (b) Fat molecule (triacylglycerol) Figure 5.11 The synthesis and structure of a fat, or triacylglycerol Describe the structure of a glycerol, a fatty acid 3 fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride.

  20. Stearic acid (a) Saturated fat and fatty acid Oleic acid cis double bond - causes bending (b) Unsaturated fat and fatty acid Figure 5.12 Examples of saturated and unsaturated fats and fatty acids Animal fats Plant/fish fats -limits the ability of fatty acids to be closely packed

  21. Lipid Structure • Glycerol - a three-carbon alcohol with a hydroxyl group attached to each carbon. • A fatty acid - a carboxyl group attached to a long carbon skeleton, often 16 to 18 carbons long. • Hydrophobic due to many nonpolar C—H bonds in the long hydrocarbon skeleton

  22. + N(CH3)3 CH2 Choline CH2 O Phosphate – Hydrophilic head P O O O CH2 CH2 CH Glycerol O O C O C O Fatty acids Hydrophilic head Hydrophobic tails Hydrophobic tails (c) Phospholipid symbol (b) Space-filling model (a) Structural formula Figure 5.13 The structure of a phospholipid polar Similar to a fat- Exception: 3rd hydroxyl group of glycerol is joined to a phosphate (neg. charge) – electronegative & hydrophilic nonpolar

  23. WATER Hydrophilic head WATER Hydrophobic tail Figure 5.14 Bilayer structure formed by self-assembly of phospholipids in an aqueous environment

  24. H3C CH3 CH3 CH3 CH3 HO Figure 5.15 Cholesterol, a steroid Carbon skeleton with 4 fused rings* Common in animal cell membranes Precursor from which all other steroids are synthesized – many of which are hormones Saturated fats and trans fats exert their negative impact on health by affecting cholesterol levels

  25. Questions - Lipids • Common names for lipids? • Smallest units? • How are they different from the other 3 macromolecules? (bonding pattern, affinity for water, carbon chain, etc.) • An ester linkage is between?

  26. Proteins • 50% of the dry mass of most cells • Protein enzymes function as catalysts • Polymers of proteins – polypeptides • Smallest units – amino acids • C, H, O, N, sometimes S

  27. Table 5.1 An Overview of Protein Functions

  28.  carbon R O H C C N OH H H Amino group Carboxyl group Amino Acid Monomers Make Proteins 5 parts: R group determines kind of a.a. thus determines properties

  29. 2 Substrate binds to enzyme. 1 Active site is available for a molecule of substrate, the reactant on which the enzyme acts. Substrate (sucrose) Glucose Enzyme (sucrase) OH H2O Fructose H O 4 Products are released. 3 Substrate is converted to products. Figure 5.16 The catalytic cycle of an enzyme

  30. CH3 CH3 CH3 CH CH2 CH3 CH3 H CH3 H3C CH3 CH2 CH O O O O H3N+ C H3N+ C H3N+ H3N+ C C C C C C H3N+ C C O– O– O– O– H H H H H Valine (Val) Leucine (Leu) Isoleucine (Ile) Glycine (Gly) Alanine (Ala) Nonpolar- hydrophobic CH3 CH2 S H2C CH2 O NH CH2 C C H2N CH2 CH2 O– CH2 O O O H H3N+ H3N+ C C C C H3N+ C C O– O– O– H H H Phenylalanine (Phe) Proline (Pro) Methionine (Met) Tryptophan (Trp) Figure 5.17 The 20 amino acids of proteins*all having carboxyl and amino groups According to the R group O O–

  31. OH NH2 O C NH2 O Polar- hydrophilic C OH SH CH2 CH3 OH CH2 CH CH2 CH2 CH2 CH2 O O O O O O H3N+ C H3N+ C H3N+ C C H3N+ C C H3N+ C C C C C H3N+ C O– O– O– O– O– O– H H H H H H Glutamine (Gln) Tyrosine (Tyr) Asparagine (Asn) Cysteine (Cys) Serine (Ser) Threonine (Thr) Basic – positive charge Acidic – negative charge NH3+ NH2 NH+ Electrically Charged- Ionized Refers only to R groups O– O –O O CH2 C NH2+ C C NH CH2 CH2 CH2 CH2 CH2 O O CH2 CH2 C CH2 C H3N+ C H3N+ C O O– O– CH2 C H3N+ CH2 C H O H O– C C H3N+ CH2 H O O– C C H3N+ H O– H Lysine (Lys) Histidine (His) Arginine (Arg) Glutamic acid (Glu) Aspartic acid (Asp)

  32. OH Peptidebond SH OH CH2 CH2 CH2 H H H C C H C N C OH H OH C C N N H DESMOSOMES O H O H O (a) H2O OH DESMOSOMES DESMOSOMES Side chains SH OH Peptidebond CH2 CH2 CH2 H H H Backbone OH C C C C C H N C N N H H O O H O Amino end(N-terminus) Figure 5.18 Making a polypeptide chain Type of reaction? Dehydration synthesis Type of bond? Peptide Carboxyl end(C-terminus) (b)

  33. pleated sheet 1 Pro Thr Gly Gly H O H 5 O O O H H H H H H R R R Thr +H3N Amino end C C C C C C H C N N H C N N C N C C C N C C C C C Gly R R R R H H H O O H O Amino acid subunits H O H H R Glu R R R Seu Lya O Cya O O O C H H C C H C H Pro H H Leu H N N N N C C C C C C C H H N C N N Met H C H 10 C N C H H C C O H H O O O Val R R R R R H H 15 Lya C C O C C N O N H H a helix Val N H N 20 H C C O Leu O Asp H R H C R C H H C C R Ala Arg R Val Gly H N H O C N O C Ser C O N C O H N H Pro C C 25 R R H N Ala 4 Levels of protein structure Primary ----------------Secondary---------------------------tertiary--------------quaternary

  34. Amino acid subunits +H3NAmino end Pro Thr Gly Gly Thr Gly Glu Seu Lys Cys Pro Leu Met Val Lys Val Leu Asp Ala Arg Val Gly Ser Pro Ala Glu Lle Asp Thr Lys Ser Tyr Trp Lys Ala Leu Gly lle Ser Pro Phe His Glu His Ala Glu Val Thr Phe Val Ala Asn lle Thr Asp Ala Tyr Arg Ser Ala Arg Pro Gly Leu Leu Ser Pro Tyr Ser Tyr Ser Thr o Thr Ala o – Val c Glu Val Carboxyl end Lys Thr Pro Asn Figure 5.20 Exploring Levels of Protein Structure: Primary structure Polypeptide chain- *a free amino end (the N-terminus), *a free carboxyl end (C-terminus) A slight change in the primary structure can affect the proteins ability to function Ex. Sickle cell anemia (substitution of valine a.a for the normal glutamic acid a.a)

  35. H H H H O O O O O O O H H H H H H H H R R R R R R R C C C C C C C C C C C C C N N N N N N N N N N N N N C C C C C C C C C C C C C C R R R R R R H H H H H H H O O O O O O O H H H H H H H H H H N N N N N N H H H 2.  Helix (coiled) O C H H H C C C R R R C C C C O O O O Figure 5.20 Exploring Levels of Protein Structure: Secondary structure – 2 forms 1.  pleated sheet (folded) H O H H Amino acidsubunits C C N N N C C C R O H C C R R H H C C H C Coils/folds caused by hydrogen bonds between the repeats R O C C O C O H N N H C C H R R H

  36. Hydrophobic interactions and van der Waalsinteractions CH CH2 H3C CH3 OH Polypeptidebackbone H3C CH3 Hydrogenbond CH O OH C CH2 CH2 S S CH2 Disulfide bridge O -O C CH2 CH2 NH3+ Ionic bond Figure 5.20 Exploring Levels of Protein Structure:Tertiary structure Bonds: Hydrogen Disulfide covalent Ionic Van der Waals interactions Peptide Determined by interactions among various R groups Among hydrophobic R groups Between polar and/or charged areas Strong covalent bonds between sulfydryl groups of 2 cysteine monomers Between charged R groups

  37. Polypeptidechain Collagen  Chains Iron Heme  Chains Hemoglobin Figure 5.20 Exploring Levels of Protein Structure:Quaternary Structure Aggregation of 2 or more polypeptide subunits Creates a 3-D shape Fibrous protein – 3 polypeptides, supercoiled, connective tissue strength (40% of human body protein) Globular protein – 4 polypeptide subunits hemoglobin Contains a nonpeptide heme + Fe atom – binds oxygen

  38. Normal hemoglobin Sickle-cell hemoglobin Primary structure . . . Primary structure . . . Val His Leu Thr Pro Glu Glu Val His Leu Thr Pro Val Glu 6 7 5 5 6 7 1 2 1 2 3 3 4 4 Secondaryand tertiarystructures Secondaryand tertiarystructures  subunit  subunit     Hemoglobin A Quaternary structure Quaternary structure Hemoglobin S     Function Molecules interact with one another tocrystallize into a fiber, capacity to carry oxygen is greatly reduced Function Molecules donot associatewith oneanother; eachcarries oxygen 10 m 10 m Red bloodcell shape Normal cells arefull of individualhemoglobinmolecules, eachcarrying oxygen Red bloodcell shape Fibers of abnormalhemoglobin deform cell into sickle shape Figure 5.21 A single amino acid substitution in a protein causes sickle-cell disease Exposed hydrophobic region

  39. Figure 5.22 Denaturation and renaturation of a protein Alterations in pH, salt concentration, temperature, exposed to an organic solvent (ether) can unravel or denature a protein (disrupts the bonding patterns) Denaturation Normal protein Denatured protein Renaturation Often can return to functional shape when the denaturing agent is removed

  40. Correctlyfoldedprotein Polypeptide Cap Hollowcylinder The cap attaches, causing the cylinder to change shape insuch a way that it creates a hydrophilic environment for the folding of the polypeptide. The cap comesoff, and the properlyfolded protein is released. Chaperonin(fully assembled) Steps of ChaperoninAction: An unfolded poly- peptide enters the cylinder from one end. 2 1 3 Figure 5.23 A chaperonin in action “folding a protein”

  41. Nucleic Acids • Store and transmit hereditary information • a polymer of nucleotides • 2 types: DNA and RNA

  42. 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 Aminoacids Polypeptide Figure 5.25 DNA  RNA  protein: a diagrammatic overview of information flow in a cell

  43. How does information from DNA make a protein? • DNA is copied to RNA in nucleus • RNA travels to ribosome • Amino acids brought to ribosome according to RNA code

  44. Nitrogenous bases-rings of C,N Pyrimidines- single ring 5’ end (5th carbon w/phosphate) NH2 O O 5’C O C C CH3 C N HN C CH HN CH 3’C CH C CH C C CH N N O N O O Nucleoside-2 parts H H H O Nitrogenous base Cytosine C Uracil (in RNA) U Thymine (in DNA) T O 5’C Purines-double rings O O O CH2 P O O NH2 O C C N N C C NH Phosphate group N 3’C HC HC Pentose sugar C CH 5’C C C N O N NH2 N N H H 3’C Adenine A Guanine G (b) Nucleotide – 3 parts OH 3’ end (3rd carbon –OH attachment) Pentose sugars (a) Polynucleotide, or nucleic acid 5’ 5’ OH OH HOCH2 HOCH2 O O H H H H 4 1’ 1’ 4 H H H H 2’ 3’ 3’ 2’ OH OH OH H Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components Figure 5.26 The components of nucleic acids Adjacent nucleotides are joined by covalent bonds called Phosphodiester linkages (formed between the –OH group on the 3’ and the phosphate on 5”)

  45. Smallest unit of a nucleic acid: • Nucleotide • Sugar • Phosphate group • Nitrogen base • Adenine • Guanine • Cytosine • Thymine

  46. 3¢ end 5¢ end G C Sugar-phosphatebackbone G C A T C G Base pair (joined by hydrogen bonding) A T A T Old strands G C A T Nucleotideabout to be added to a new strand A T A T C G C G T 3¢ end A A C A C G G T G C T G A T C C T A G 5¢ end G A A T C C G T A A T T T G A A A A C C T T A Newstrands T G 3¢ end 5¢ end T G A A C T 5¢ end 3¢ end Figure 5.27 The DNA double helix and its replication Hydrogen bonds Hold sides together

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