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The Structure and Function of Macromolecules Chapter 5 The Structure and Function of Macromolecules

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? Carbohydrates Proteins Lipids Nucleic acids How are they all similar? All large polymers made of smaller monomers All formed the same way

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

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? How are they all similar? What are carbohydrates & what are they made of? Sugars Made of monosaccharides CH20 Sugars end in -ose Nutrient for cells (1° glucose) Carbon skeleton is used for other organic molecules

Figure 5.3 Examples of monosaccharides Triose sugars (C3H6O3) Pentose sugars (C5H10O5) Hexose sugars (C6H12O6) H C OH H C OH HO C H H C OH C O HO C H H C O Aldoses Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Ketoses Fructose Figure 5.3

Figure 5.4 Linear & ring forms of glucose H H C OH HO C H H C O C 1 2 3 4 5 6 OH 4C 6CH2OH 5C H OH 2 C 1C 3 C 2C 1 C CH2OH HO 3 2 (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

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? How are they all similar? What are carbohydrates & what are they made of? How are monomers added to carbs? 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. 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. (a) (b) H HO H OH OH O CH2OH H2O 1 2 4 1– 4 glycosidic linkage 1–2 glycosidic linkage Glucose Fructose Maltose Sucrose

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? How are they all similar? What are carbohydrates & what are they made of? How are monomers added to carbs? What are polysaccharides used for? Energy storage Starch – plants Glycogen – animals Structural support Cellulose Chitin

Chapter 5 The Structure and Function of Macromolecules Mitochondria Giycogen granules Chloroplast Starch Amylose Amylopectin 1 m 0.5 m (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide Glycogen

(b) Starch: 1– 4 linkage of (c) Cellulose: 1– 4 linkage CH2OH CH2OH H C OH H H O H O OH H H 4 OH HO C H H 4 OH H 1 HO OH HO H C OH H H OH H OH H C OH  glucose H C OH  glucose  and  glucose ring structures CH2OH CH2OH CH2OH CH2OH O O O O 1 4 1 OH 4 1 4 1 OH OH HO O O OH O O OH OH OH OH (b) Starch: 1– 4 linkage of  glucose monomers CH2OH OH CH2OH OH O O O OH O OH OH HO 1 4 O OH OH O O OH CH2OH OH CH2OH (c) Cellulose: 1– 4 linkage of  glucose monomers 6. Why do we poop corn?

Chapter 5 The Structure and Function of Macromolecules Cellulose molecules Plant cells 0.5 m Cell walls Cellulose microfibrils in a plant cell wall  Microfibril CH2OH OH O Glucose monomer Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. A cellulose molecule is an unbranched  glucose polymer. Figure 5.8 Cellulose

Chapter 5 The Structure and Function of Macromolecules (a) The structure of the chitin monomer. O CH2OH OH H NH C CH3 (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.

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? How are they all similar? What are carbohydrates & what are they made of? How are monomers added to carbs? What are polysaccharides used for? Why do we poop corn? What are some common lipids? Fats Phospholipids Steroids Oils Waxes

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? How are they all similar? What are carbohydrates & what are they made of? How are monomers added to carbs? What are polysaccharides used for? Why do we poop corn? What are some common lipids? How are fats made?

Figure 5.11 The synthesis and structure of a fat, or triacylglycerol (b) Fat molecule (triacylglycerol) H O H C OH Glycerol Fatty acid (palmitic acid) HO O (a) Dehydration reaction in the synthesis of a fat Ester linkage

Chapter 5 The Structure and Function of Macromolecules What are the 4 major macromolecules? How are they all similar? What are carbohydrates & what are they made of? How are monomers added to carbs? What are polysaccharides used for? Why do we poop corn? What are some common lipids? How are fats made? What is the difference between a saturated & unsaturated fat?

Figure 5.12 Examples of saturated and unsaturated fats and fatty acids (a) Saturated fat and fatty acid Stearic acid (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid

Saturated vs Unsaturated Fats No double bonds (C-C) - Double bonds (C=C) Carbons are saturated - Carbons not saturated Solid at RT - Oil at RT Animal fats - Plant or fish fats Butter - Vegetable oil Bacon grease - Olive oil What are trans fats? Formed by hydrogenation C=C without the “kink”

Saturated vs Unsaturated Fats No double bonds (C-C) - Double bonds (C=C) Carbons are saturated - Carbons not saturated Solid at RT - Oil at RT Animal fats - Plant or fish fats Butter - Vegetable oil Bacon grease - Olive oil What are the functions of fats? Energy storage (2X carbs) Cushion Insulation

Figure 5.13 The structure of a phospholipid Hydrophilic head CH2 N(CH3)3 O P CH C Choline Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails + – Amphipathic – molecules both polar & non-polar

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

Figure 5.15 Cholesterol, a steroid H3C

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Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? Amino acids How are all amino acids similar? H N C R O OH Amino group Carboxyl  carbon

Figure 5.17 The 20 amino acids of proteins H3N+ C CH3 CH CH2 NH H2C H2N Nonpolar Glycine (Gly) Alanine (Ala) Valine (Val) Leucine (Leu) Isoleucine (Ile) Methionine (Met) Phenylalanine (Phe) Tryptophan (Trp) Proline (Pro) H3C

Polar Electrically charged OH CH2 C H H3N+ O CH3 CH SH NH2 Polar Electrically charged –O NH3+ NH2+ NH+ NH Serine (Ser) Threonine (Thr) Cysteine (Cys) Tyrosine (Tyr) Asparagine (Asn) Glutamine (Gln) Acidic Basic Aspartic acid (Asp) Glutamic acid (Glu) Lysine (Lys) Arginine (Arg) Histidine (His)

Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? How are all amino acids similar? How are amino acids connected? Dehydration (condensation) rxn Creates a peptide bond

Figure 5.18 Making a polypeptide chain Carboxyl end (C-terminus) DESMOSOMES OH CH2 C N H O Peptide bond SH Side chains H2O Amino end (N-terminus) Backbone (a) (b)

Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? How are all amino acids similar? How are amino acids connected? What are the 4 levels of protein structure? 1° (Primary) – aa sequence (determined by DNA sequence) 2° (Secondary) – based on H-bonds 3° (Tertiary) – overall globular shape – 3D structure 4° (Quaternary) – several 3° polypeptides (subunits)

Figure 5.20 Primary structure of a protein Based on amino acid sequence Each protein has a unique sequence Like the alphabet (letters = aa) – Amino acid subunits +H3N Amino end o Carboxyl end c Gly Pro Thr Glu Seu Lys Cys Leu Met Val Asp Ala Arg Ser lle Phe His Asn Tyr Trp Lle

Figure 5.20 Secondary structure of a protein  helix  pleated sheet Amino acid subunits N H R Based on H-bonds α-helix - β-pleated sheet adjacent polar aa - after folding, polar aa become neighbors and form H-bonds

Figure 5.20 Tertiary structure overall globular shape – 3D structure each protein has unique 3D shape recall carbon sets the 3D shape based on 1° structure (aa sequence) rearranged the alphabet to get new words Disulfide bridge 2 cysteine amino acids covalent bond van der Waals interactions hydrophobic interactions ionic bonds occasional H-bonds CH2 O H O C OH NH3+ -O S CH CH3 H3C Hydrophobic interactions and van der Waals interactions Polypeptide backbone Hydrogen bond Ionic bond Disulfide bridge

Figure 5.20 Quarternary structure Polypeptide chain Collagen  Chains  Chains Hemoglobin Iron Heme more than one 3° polypeptide (subunit) needed for biological activity not all proteins have quarternary structure # of subunits varies by protein

Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? How are all amino acids similar? How are amino acids connected? What are the 4 levels of protein structure? How much does sequence (structure) influence function? Sickle cell anemia

Sickle-cell hemoglobin Figure 5.21 A single amino acid substitution in a protein causes sickle-cell disease Primary structure Secondary and tertiary structures Quaternary structure Function Red blood cell shape Hemoglobin A Molecules do not associate with one another; each carries oxygen Normal cells are full of individual hemoglobin molecules, each carrying oxygen   10 m Hemoglobin S Molecules interact with one another to crystallize into a fiber, capacity to carry oxygen is greatly reduced Fibers of abnormal hemoglobin deform cell into sickle shape  subunit 1 2 3 4 5 6 7 Normal hemoglobin Sickle-cell hemoglobin . . . Val His Leu Thr Pro Glu Glu Val His Leu Thr Pro Val Glu

Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? How are all amino acids similar? How are amino acids connected? What are the 4 levels of protein structure? How much does sequence (structure) influence function? What happens to proteins if they get too hot or experience a change in pH? Denaturation Renaturation Denatured protein Normal protein

Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? How are all amino acids similar? How are amino acids connected? What are the 4 levels of protein structure? How much does sequence (structure) influence function? What happens to proteins if they get too hot or experience a change in pH? What do proteins do?

Table 5.1 Protein function ↓

Chapter 5 The Structure and Function of Macromolecules 10. What are the monomers of proteins? How are all amino acids similar? How are amino acids connected? What are the 4 levels of protein structure? How much does sequence (structure) influence function? What happens to proteins if they get too hot or experience a change in pH? What do proteins do? What are the different types of nucleic acids? DNA – deoxyribonucleic acid RNA – ribonucleic acid mRNA – messenger tRNA – transfer rRNA – ribosomal What are the monomers of nucleic acids? Nucleotides What makes up the monomers?

(c) Nucleoside components Figure5.26 Components of nucleic acids 3’C CH Uracil (in RNA) U 5’ end 5’C O 3’ end OH Nitrogenous base Nucleoside O O P CH2 Phosphate group Pentose sugar (b) Nucleotide C N H NH2 HN CH3 Cytosine Thymine (in DNA) T HC NH Adenine A Guanine G Purines HOCH2 5’ 4 3’ 2’ 1’ 3’ 2’ Pentose sugars Deoxyribose (in DNA) Ribose (in RNA) Nitrogenous bases Pyrimidines (c) Nucleoside components (a) Polynucleotide, or nucleic acid

Figure 5.27 DNA Double helix 3¢ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand A 5¢ end New strands C G T