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1 Macromolecules – Are large molecules composed of a large number of repeated subunits – Are complex in their structures Figure 5.1.

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Presentation on theme: "1 Macromolecules – Are large molecules composed of a large number of repeated subunits – Are complex in their structures Figure 5.1."— Presentation transcript:

1 1 Macromolecules – Are large molecules composed of a large number of repeated subunits – Are complex in their structures Figure 5.1

2 2 Macromolecules MacromoleculeSubunit Complex Carbohydrates (e.g. starch) Simple sugar (e.g. glucose) Lipid (triglycerides)Glycerol and fatty acids ProteinAmino Acids Nucleic Acids (DNA or RNA)Nucleotides

3 3 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

4 4 The Synthesis and Breakdown of Macromolecules Monomers form larger molecules by condensation reactions called dehydration synthesis (a) Dehydration reaction in the synthesis of a polymer HOH 1 2 3 H 1 23 4 H H2OH2O Short polymer Unlinked monomer Longer polymer Dehydration removes a water molecule, forming a new bond Figure 5.2A

5 5 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

6 6 The Synthesis and Breakdown of Macromolecules Polymers can disassemble by – Hydrolysis (addition of water molecules to lyse or “break apart” the macromolecule) (b) Hydrolysis of a polymer HO 1 2 3 H H 1 2 3 4 H2OH2O H Hydrolysis adds a water molecule, breaking a bond Figure 5.2B

7 7 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

8 8 An immense variety of polymers can be built from a small set of monomers

9 Question 1 How many molecules of water are needed to completely hydrolyze a polymer that is 10 monomers long? 9

10 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


12 12 Carbohydrates Serve as fuel and building material Include both sugars and their polymers (starch, cellulose, etc.)

13 13 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

14 14 Examples of monosaccharides Triose sugars (C 3 H 6 O 3 ) Pentose sugars (C 5 H 10 O 5 ) Hexose sugars (C 6 H 12 O 6 ) H C OH HO C H H C OH HO C H H C OH C O H C OH HO C H H C OH C O H H H HHH H H HHH H H H C CCC O O O O Aldoses Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Ketoses Fructose Figure 5.3

15 15 Monosaccharides – May be linear – Can form rings H H C OH HO C H H C OH H C O C H 1 2 3 4 5 6 H OH 4C4C 6 CH 2 OH 5C5C H OH C H OH H 2 C 1C1C H O H OH 4C4C 5C5C 3 C H H OH OH H 2C2C 1 C OH H CH 2 OH H H OH HO H OH H 5 3 2 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. OH 3 O H O O 6 1 Figure 5.4

16 α glucose vs. β glucose 16

17 17 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

18 18 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 H OH H OH O H CH 2 OH H HO H H OH H OH O H CH 2 OH H O H H OH H OH O H CH 2 OH H H2OH2O H2OH2O H H O H HO H OH O H CH 2 OH HO OH H CH 2 OH H OH H H HO OH H CH 2 OH H OH H O O H OH H CH 2 OH H OH H O H OH CH 2 OH H HO O CH 2 OH H H OH O O 1 2 1 4 1– 4 glycosidic linkage 1–2 glycosidic linkage Glucose Fructose Maltose Sucrose OH H H Figure 5.5

19 19 Polysaccharides – Are polymers of sugars with several hundred to several thousand monosaccharide subunits held together by glycosidic linkages – Serve many roles in organisms

20 20 Storage Polysaccharides Starch – Is a polymer consisting entirely of glucose monomers – Is the major storage form of glucose in plants Chloroplast Starch Amylose Amylopectin 1  m (a) Starch: a plant polysaccharide Figure 5.6

21 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 22

23 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

24 24 Mitochondria Giycogen granules 0.5  m (b) Glycogen: an animal polysaccharide Glycogen Figure 5.6

25 25 Structural Polysaccharides Cellulose – Is a polymer of glucose – Has different glycosidic linkages than starch – The main structural polysaccharide in plants and plant cell walls

26 26 – Cellulose is a straight chain polymer of β glucose with 1-4 glycosidic linkages (c) Cellulose: 1– 4 linkage of  glucose monomers H O O CH 2 OH H OH H H H H HO 4 C C C C C C H H H OH H H O CH 2 OH H H H OH H H HO 4 OH CH 2 OH O OH HO 4 1 O CH 2 OH O OH O CH 2 OH O OH CH 2 OH O OH O O CH 2 OH O OH HO 4 O 1 OH O O CH 2 OH O OH O O (a)  and  glucose ring structures (b) Starch: 1– 4 linkage of  glucose monomers 1  glucose  glucose CH 2 OH 1 4 4 1 1 Figure 5.7 A–C

27 27 Plant cells 0.5  m Cell walls Cellulose microfibrils in a plant cell wall  Microfibril CH 2 OH OH O O O CH 2 OH O O OH O CH 2 OH OH O O CH 2 OH O O OH CH 2 OH O O OH O O CH 2 OHOH CH 2 OHOH O O CH 2 OH OH O CH 2 OH O O OHCH 2 OH OH  Glucose monomer O O O O O O 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. OH O O Cellulose molecules Figure 5.8 – Unlike amylose and amylopectin (starches), cellulose molecules are neither coiled nor branched

28 28 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 Figure 5.9

29 29 Chitin, another important structural polysaccharide – Is found in the exoskeleton of arthropods – Can be used as surgical thread (a) The structure of the chitin monomer. O CH 2 OH OH H H H NH C CH 3 O H H (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. OH Figure 5.10 A–C


31 31 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

32 Lipids Fats Phospholipids Steroids 32

33 33 Fats – Are constructed from two types of smaller molecules: single glycerol and three fatty acids Fatty Acid

34 34 Glycerol


36 36 Saturated fatty acids – Have the maximum number of hydrogen atoms possible – Have no double bonds – Are solid at room temperature (e.g. animal fats) (a) Saturated fat and fatty acid Stearic acid Figure 5.12

37 37 Unsaturated fatty acids – Have one or more double bonds, causing a bend in its structure – Are liquids at room temperature (e.g. vegetable fats) (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid Figure 5.12

38 Unsaturated Fats Monounsaturated fats (MUFA) – Have one double bond in their fatty acids 38 Polyunsaturated fats (PUFA) Have more than one double bond in their fatty acid chains


40 40

41 41 Phospholipids – Have only two fatty acids – Have a phosphate group instead of a third fatty acid

42 42 Phospholipid structure – Consists of a hydrophilic “head” and hydrophobic “tails” CH 2 O P O O O CH CH 2 OO C O C O Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head CH 2 Choline + Figure 5.13 N(CH 3 ) 3

43 Micelles When phospholipids are added to water, they form micelles 43

44 44 Phospholipid Bilayer – Results in a phospholipid bilayer arrangement found in cell membranes Hydrophilic head WATER Hydrophobic tail Figure 5.14 Water and other polar and ionic materials cannot pass through the membrane except by the help of proteins in the membrane

45 45 Steroids – Are lipids that have a carbon skeleton consisting of four fused rings – Contain many different functional groups

46 46 One steroid, cholesterol – Is found in cell membranes – Is a precursor for some hormones HO CH 3 H3CH3C Figure 5.15


48 48 Nucleic Acids Nucleic acids store and transmit hereditary information There are two types of nucleic acids – Deoxyribonucleic acid (DNA) – Ribonucleic acid (RNA)

49 49 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 Function of DNA and RNA

50 50 The Structure of Nucleic Acids Nucleic acids (also called Polynucleotides) – Are polymers made up of individual nucleotide monomers (a) Polynucleotide, or nucleic acid 3’C 5’ end 5’C 3’C 5’C 3’ end OH Figure 5.26 O O O O

51 51 Each Nucleotide contains – Sugar + phosphate + nitrogen base Nitrogenous base Nucleoside O O OO OO P CH 2 5’C 3’C Phosphate group Pentose sugar (b) Nucleotide Figure 5.26 O

52 52 Nucleotide Monomers (c) Nucleoside components Figure 5.26 CH Uracil (in RNA) U Ribose (in RNA) Nitrogenous bases Pyrimidines C N N C O H NH 2 CH O C N H HN C O C CH 3 N HN C C H O O Cytosine C Thymine (in DNA) T N HC N C C N C CH N NH 2 O N HC N H H C C N NH C NH 2 Adenine A Guanine G O HOCH 2 H H H OH H O HOCH 2 H H H OH H Pentose sugars Deoxyribose (in DNA) Ribose (in RNA) OH CH Uracil (in RNA) U 4’ 5”5” 3’ OH H 2’ 1’ 5”5” 4’ 3’ 2’ 1’ Pyrimidines (single ring) Purines (double ring)

53 53 Nucleotide Polymers 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 3’C 5’ end 5’C 3’C 5’C 3’ end OH Figure 5.26 O O O O

54 54 Gene The sequence of bases along a nucleotide polymer – Is unique for each gene

55 55 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

56 56 The DNA double helix – Consists of two antiparallel nucleotide strands 3’ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand A 3’ end 5’ end New strands 3’ end 5’ end Figure 5.27

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