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Macromolecules – Are large molecules composed of a large number of repeated subunits – Are complex in their structures Figure 5.1 1 Macromolecules Macromolecule Subunit Complex Carbohydrates (e.g. starch) Simple sugar (e.g. glucose) Lipid (triglycerides) Glycerol and fatty acids Protein Amino Acids Nucleic Acids (DNA or RNA) Nucleotides 2 • A polymer – Is a long molecule consisting of many similar smaller building blocks called monomers – Specific monomers make up each macromolecule – E.g. amino acids are the monomers for proteins 3 The Synthesis and Breakdown of Macromolecules • Monomers form larger molecules by condensation reactions called dehydration synthesis HO 1 2 3 H Unlinked monomer Short polymer Dehydration removes a water molecule, forming a new bond HO 1 2 H HO 3 H 2O 4 H Longer polymer Figure 5.2A (a) Dehydration reaction in the synthesis of a polymer 4 Condensation Reactions • Requires energy because new bonds are being formed • Are also called a anabolic reactions because smaller molecules join together to form larger molecules small LARGE 5 The Synthesis and Breakdown of Macromolecules • Polymers can disassemble by – Hydrolysis (addition of water molecules to lyse or “break apart” the macromolecule) HO 1 2 3 4 Hydrolysis adds a water molecule, breaking a bond HO 1 2 3 H Figure 5.2B (b) Hydrolysis of a polymer H H 2O HO H 6 Hydrolysis • Releases energy because bonds are being broken • Are also called a Catabolic reactions because larger molecules are being broken down into smaller subunits LARGE small 7 • An immense variety of polymers can be built from a small set of monomers 8 Question 1 • How many molecules of water are needed to completely hydrolyze a polymer that is 10 monomers long? 9 Question 2 • After you eat a slice of apple, which reactions must occur for the amino acid monomers in the protein of the apple to be converted into proteins in your body? Amino acids are incorporated into proteins in your body by dehydration reactions CARBOHYDRATES 11 Carbohydrates • Serve as fuel and building material • Include both sugars and their polymers (starch, cellulose, etc.) 12 Sugars • Monosaccharides – Are the simplest sugars – Contain a single chain of carbon atoms with hydroxyl groups – They also contain carbonyl (aldehyde or keytone) groups – Can be combined into polymers 13 • Examples of monosaccharides Triose sugars (C3H6O3) H O Aldoses C Pentose sugars (C5H10O5) H O C H O C O C C OH H C OH H C OH H C OH H H C OH H C OH H C OH H C OH H C OH H C OH H C OH H Ribose H Ketoses H H Glyceraldehyde H H C OH H C OH HO C H HO C H HO C H H H Glucose Galactose H H C OH H C OH H C OH C O C O C O H C OH H C OH HO C H H H C OH H C OH Dihydroxyacetone H C OH H C OH H Ribulose Figure 5.3 Hexose sugars (C6H12O6) H C OH H Fructose 14 • Monosaccharides – May be linear – Can form rings O H 1C H HO 2 3 C 6CH OH 2 OH H C H 4 H H H C C C H OH 4C OH OH OH 5C H O H OH 5 6 5C 6CH OH 2 3 C H 2C O H H 4C 1C CH2OH O OH H OH 3C 6 H 1C H 2C 4 OH H H H OH HO 3 1 OH 2 OH H H O 5 OH OH H Figure 5.4 (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. 15 α glucose vs. β glucose 16 • Oligosaccharides – contain two or three monosaccarides attached by covalent bonds called glycosidic linkages – Disaccharides • Consist of two monosaccharides • Are joined by a single glycosidic linkage 17 (a) 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. CH2OH CH2OH H O H OH H OH HO H H H HO O H OH H H OH CH2OH H OH OH O H H OH CH2OH H 1 H HO O H 4 H OH H H OH O H OH 1–4 glycosidic linkage H OH OH H2O Glucose Glucose CH2OH H (b) Dehydration reaction HO 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. O H OH H H CH2OH H OH HO H CH2OH O H H O H H OH HO CH2OH OH OH Maltose H CH2OH 1–2 glycosidic 1 linkage O H H 2 H HO O HO H OH CH2OH OH H H2O Glucose Fructose Sucrose Figure 5.5 18 Polysaccharides • Polysaccharides – Are polymers of sugars with several hundred to several thousand monosaccharide subunits held together by glycosidic linkages – Serve many roles in organisms 19 Storage Polysaccharides Chloroplast Starch • Starch – Is a polymer consisting entirely of glucose monomers – Is the major storage form of glucose in plants 1 m Amylose Figure 5.6 Amylopectin (a) Starch: a plant polysaccharide 20 Two types of Starch • Amylose – Straight chain polymer of α (alpha) glucose – Has 1-4 glycosidic linkages • Amylopectin – Branched chains of α glucose and β glucose – Has 1-4 glycosidic linkages in the main chains and 1-6 glycosidic linkages at the branch points 21 22 Glucose Storage in Animals • Glycogen – Consists of glucose monomers – Similar to Amylopectin (has 1-4 and 1-6 glycosidic linkages), but there are more branches in glycogen – Stored in muscle and liver 23 Mitochondria Giycogen granules 0.5 m Glycogen Figure 5.6 (b) Glycogen: an animal polysaccharide 24 Structural Polysaccharides • Cellulose – Is a polymer of glucose – Has different glycosidic linkages than starch – The main structural polysaccharide in plants and plant cell walls 25 – Cellulose is a straight chain polymer of β glucose with 1-4 glycosidic linkages H O C CH2OH H 4 H OH O H H OH HO H OH glucose H C OH HO C H CH2OH O H OH H H 4 H C OH H C OH H C OH HO OH 1 H H OH glucose (a) and glucose ring structures CH2OH CH2OH O HO O 4 1 OH O 1 OH O 4 O 1 OH OH OH CH2OH CH2OH O O 4 1 OH O OH OH (b) Starch: 1– 4 linkage of glucose monomers CH2OH O HO Figure 5.7 A–C OH OH O 1 4 OH OH CH2OH O O OH O O CH2OH OH OH (c) Cellulose: 1– 4 linkage of glucose monomers OH O CH2OH OH 26 – Unlike amylose and amylopectin (starches), cellulose molecules are neither coiled nor branched Cellulose microfibrils in a plant cell wall Cell walls Microfibril About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. 0.5 m Plant cells OH CH2OH CH2OH O O O O OH OH OH O O O OH OH CH2OH Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. Figure 5.8 O CH2OH O OH O OH CH2OH O O O OH OH OH OH O O CH2OH OH OH O O CH2OH CH2OH O O OH OH CH2OH O O OH OH Glucose OH OH O O CH2OH OH Cellulose molecules OH O O CH2OH OH OH O O CH2OH A cellulose molecule is an unbranched glucose polymer. monomer 27 • Cellulose is difficult to digest – However, it does contribute to “roughage” in the diet fibre – Cows have microbes in their stomachs to facilitate this process 28 Figure 5.9 • Chitin, another important structural polysaccharide – Is found in the exoskeleton of arthropods – Can be used as surgical thread CH2OH O OH H H OH H OH H H NH C O CH3 (a) The structure of the chitin monomer. Figure 5.10 A–C (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. 29 LIPIDS Lipids • Lipids are hydrophobic molecules • Mostly C-H (non-polar) • are the one class of large biological molecules that do not consist of polymers • Uses: structure of cell membranes, energy source 31 Lipids • Fats • Phospholipids • Steroids 32 Fats – Are constructed from two types of smaller molecules: • single glycerol and • three fatty acids Fatty Acid 33 Glycerol 34 ESTER LINKAGE 35 • Saturated fatty acids – Have the maximum number of hydrogen atoms possible – Have no double bonds – Are solid at room temperature (e.g. animal fats) Stearic acid 36 (a) Saturated fat and fatty acid Figure 5.12 • Unsaturated fatty acids – Have one or more double bonds, causing a bend in its structure – Are liquids at room temperature (e.g. vegetable fats) Oleic acid Figure 5.12 (b) Unsaturated fat and fatty acid cis double bond causes bending 37 Unsaturated Fats • Monounsaturated fats (MUFA) – Have one double bond in their fatty acids •Polyunsaturated fats (PUFA) Have more than one double bond in their fatty acid chains 38 40 Phospholipids – Have only two fatty acids – Have a phosphate group instead of a third fatty acid 41 • Phospholipid structure – Consists of a hydrophilic “head” and hydrophobic “tails” CH2 CH2 O O P O– + N(CH3)3 Choline Phosphate O CH2 CH O O C O C CH2 Glycerol O Fatty acids Hydrophilic head Hydrophobic tails Figure 5.13 (a) Structural formula (b) Space-filling model (c) Phospholipid symbol 42 Micelles • When phospholipids are added to water, they form micelles 43 Phospholipid Bilayer – Results in a phospholipid bilayer arrangement found in cell membranes Hydrophilic head WATER Water and other polar and ionic materials cannot pass through the membrane except by the help of proteins in the membrane WATER Hydrophobic tail re 5.14 44 Steroids • Steroids – Are lipids that have a carbon skeleton consisting of four fused rings – Contain many different functional groups 45 • One steroid, cholesterol – Is found in cell membranes – Is a precursor for some hormones H 3C CH3 CH3 CH3 CH3 Figure 5.15 HO 46 NUCLEIC ACIDS Nucleic Acids • Nucleic acids store and transmit hereditary information • There are two types of nucleic acids – Deoxyribonucleic acid (DNA) – Ribonucleic acid (RNA) 48 Function of DNA and RNA • DNA – Stores information for the synthesis of specific proteins – Found in the nucleus of cells • RNA – Reads information in DNA – Transports information to protein building structures within cell 49 The Structure of Nucleic Acids • Nucleic acids (also called Polynucleotides) 5’ end 5’C O 3’C – Are polymers made up of individual nucleotide monomers O O 5’C (a) Polynucleotide, or nucleic acid Figure 5.26 O 3’C OH 3’ end 50 • Each Nucleotide contains – Sugar + phosphate + nitrogen base Nucleoside Nitrogenous base O O P 5’C O CH2 O O Phosphate group Figure 5.26 3’C Pentose sugar (b) Nucleotide 51 Nucleotide Monomers Nitrogenous bases Pyrimidines NH2 (c) Nucleoside components C N O O C HN CH CH N C Cytosine C N CH3 C CH HC C C N H CH CH CH CH H Thymine (in DNA) T Uracil (inRNA) RNA) Uracil (in UU C N CH N Pyrimidines (single ring) O N C C HC N H Adenine A NH C N NH2 Guanine G Purines (double ring) Pentose sugars 5” HOCH2 OH O H H 4’ C O NH2 N C HN N H O H C O H 3’ OH 2’ 1’ H H Deoxyribose (in DNA) Figure 5.26 5” HOCH2 H H 4’ H OH O 3’ OH 2’ 1’ H OH Ribose Ribose (in (in RNA) RNA) 52 e 5.26 Nucleotide Polymers 5’ end 5’C • nucleotides linked by the–OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next • Phosphodiester bond O 3’C O O 5’C O 3’C OH 3’ end 53 Gene • The sequence of bases along a nucleotide polymer – Is unique for each gene 54 The DNA Double Helix • Have two polynucleotides that spiral around each other • held together by hydrogen bonds between nitrogenous bases – A (adenine) will always bond with T (thymine – DNA only), or U (uracil – RNA only) 2 hydrogen bonds – C (cytosine) will always bond with G (guanine) 3 hydrogen bonds 55 • The DNA double helix – Consists of two antiparallel nucleotide strands 5’ end 3’ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands A 3’ end Nucleotide about to be added to a new strand 5’ end 3’ end Figure 5.27 5’ end New strands 3’ end 56