1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 5 The Structure and Function of Macromolecules

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: The Molecules of Life – Another level in the hierarchy of biological organization is reached when small organic molecules are joined together

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Macromolecules – Are large molecules composed of smaller molecules – Are complex in their structures

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 5.1: Most macromolecules are polymers, built from monomers Three of the classes of life’s organic molecules are polymers – Carbohydrates – Proteins – Nucleic acids The fourth class is not a polymer (the lipids)

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A polymer (poly=many; mer=part) – Is a long molecule consisting of many similar building blocks called monomers (mono=single)

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Synthesis and Breakdown of Polymers Monomers form larger molecules by condensation reactions called dehydration (polymerization) reactions Requires energy Requires enzymes

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polymers can disassemble by – Hydrolysis: (hydro= water; lysis= break) Releases energy Enzymes speed up hydrolysis

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Diversity of Polymers Each class of polymer – Is formed from a specific set of monomers 1 2 3 HOH Although organisms share the same limited number of monomer types, each organism is unique based on the arrangement of monomers into polymers An immense variety of polymers can be built from a small set of monomers

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 5.2: Carbohydrates serve as fuel and building material Carbohydrates – Include both sugars and their polymers – Monomers of carbohydrates are simple sugars called Monosaccharides – Polymers are formed by condensation reaction – Are classified based on the number of simple sugars

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sugars Monosaccharides – Mono=single, sacchar=sugar – Are the simple sugars in which C, H and O are occur in the ratio of CH2O. – Are major nutrients for the cell – Can be produced by photosynthesis from CO 2, H 2 O and sunlight. – Store energy in their chemical bonds which are harvested by cellular respiration. – Can be incorporated as monomers into disaccharides and polysaccharides

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Monosaccharides – May be linear – Can form rings

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Disaccharides – (Di=two; sacchar=sugar) – consists of two monosaccharides joined by glycosidic linkage – Maltose (malt sugar) = glucose + glucose – Lactose (milk sugar) = glucose + galactose – Sucrose (table sugar) = glucose + fructose

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polysaccharides – Macromolecules that are polymers of a few hundred or thousand of monosaccharides. – Formed by linking monomers in condensation reaction – Have two important biological functions: i. energy storage (starch and glycogen) ii. structural support (cellulose and chitin).

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Storage Polysaccharides Starch – Is a polymer consisting entirely of glucose monomers

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Is the major storage form of glucose in plants – Stored as granules within plant organelles called plastids – Amylose the simplest form is an unbranched polymer. – Amylopectin is branched polymer – Most animals have digestive enzymes to hydrolyse starch Starch

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Large glucose polymer that is more highly branched than amylopectin Is the major storage form of glucose in animals Stored in the muscles and liver of humans and other vertebrates Glycogen

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structural Polysaccharides Cellulose – Linear unbranched polymer of glucose – Differ from starch in its glycosidic linkages – Cellulose and starch have different three- dimensional shapes and properties as a result of differences in glycosidic linkages.

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Has different glycosidic linkages than starch

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Is a major component of the tough walls that enclose plant cells

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellulose is difficult to digest – Cows have microbes in their stomachs to facilitate this process

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chitin, another important structural polysaccharide – Is found in the exoskeleton of arthropods – Can be used as surgical thread

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 5.3: Lipids are a diverse group of hydrophobic molecules Lipids – Are the one class of large biological molecules that do not consist of polymers – Share the common trait of being hydrophobic

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fats – Are constructed from two types of smaller molecules – a single glycerol (a three carbon alcohol) and usually three fatty acids (carboxylic acid) (b) Fat molecule (triacylglycerol) H H H H H H H H H H H H H H H H O Figure 5.11 Fats are formed by a condensation reaction which links glycerol to fatty acids by an Ester linkage.

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fatty acids – composed of a carboxyl group at one end (head) and an attached hydrocarbon (C-H) chain (tail) – Nonpolar C-H bonds make the chain hydrophobic (not water soluble) – Vary in the length and number and locations of double bonds they contain

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Saturated fatty acids – Have the maximum number of hydrogen atoms possible – Have no double bonds

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Unsaturated fatty acids – Have one or more double bonds

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Saturated fatty acids Unsaturated fatty acids - No double bonds between carbons of fatty acid tail. - Carbon skeleton of fatty acid is bonded to maximum number of hydrogens -Usually a solid at room temperature -Most animal fats - One or more double bonds between carbons of fatty acid tail -Tail kinks at each C=C, so molecules do not pack enough to solidify at room temperature. -Usually a liquid at room temperature - Most plant fats

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipids – Have only two fatty acids – Have a phosphate group instead of a third fatty acid

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phospholipid structure – Consists of a hydrophilic “head” and hydrophobic “tails” → it’s amphiphatic

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The structure of phospholipids – Results in a bilayer arrangement found in cell membranes

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Steroids – Are lipids characterized by a carbon skeleton consisting of four fused rings

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One steroid, cholesterol – Is found in cell membranes – Is a precursor for some hormones

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 5.4: Proteins have many structures, resulting in a wide range of functions – Proteins Have many roles inside the cell

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of protein functions - Are abundant, forming about 50% of cellular dry weight - Have important functions in the cell: 1.structural support 2.storage (of amino acids) 3.transport (e.g. hemoglobin) 4. signaling (chemical messengers) 5.cellular response (receptor proteins) 6.movement (contractile proteins) 7.defense (antibodies) 8.catalysts of biochemical reactions (enzymes

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Enzymes – Are a type of protein that acts as a catalyst, speeding up chemical reactions

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polypeptides – Are polymers of amino acids A protein – Consists of one or more polypeptides

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amino Acid Monomers Amino acids – Are organic molecules possessing both carboxyl and amino groups – Differ in their properties due to differing side chains, called R groups

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 20 different amino acids make up proteins

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amino Acid Polymers Amino acids – Are linked by peptide bonds

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Determining the Amino Acid Sequence of a Polypeptide The amino acid sequences of polypeptides – Were first determined using chemical means – Can now be determined by automated machines

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protein Conformation and Function A protein’s specific conformation – Determines how it functions

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two models of protein conformation

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Four Levels of Protein Structure Primary structure – Is the unique sequence of amino acids in a polypeptide – determined by genes – slight change can effect the protein conformation and function (e.g. sickle- cell hemoglobin)

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Secondary structure – Is the folding or coiling of the polypeptide into a repeating configuration – Includes the  helix and the  pleated sheet – Stabilized by hydrogen bonding H H Figure 5.20

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tertiary structure – Is the overall three-dimensional shape of a polypeptide – Results from interactions between amino acids and R groups

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Quaternary structure – Is the overall protein structure that results from the aggregation of two or more polypeptide subunits

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The four levels of protein structure

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Determines Protein Conformation? Protein conformation – A proteins three-dimensional shape is a consequence of the interactions responsible for the secondary and tertiary structures. – This conformation is influenced by physical & chemical environmental conditions. – If a protein’s environment is changed, it may become denatured and lose its conformation.

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Denaturation – Is when a protein unravels and loses its native conformation – A protein can be denatured by: transfer to organic solution. Chemical agent that disrupt hydrogen bonds. Excessive heat that disrupt weak interactions

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 5.5: Nucleic acids store and transmit hereditary information Genes – Are the units of inheritance – Program the amino acid sequence of polypeptides – Are made of nucleic acids

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Roles of Nucleic Acids There are two types of nucleic acids – Deoxyribonucleic acid (DNA) – Ribonucleic acid (RNA)

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings DNA – Stores information for the synthesis of specific proteins – contains genes that program all cell activity. – Contain directions for its own replication – Is copied and passed from one generation to another. – In eukaryotic cells, is found in the nucleus. – Makes up genes that contain instructions for protein synthesis.

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Directs RNA synthesis – Directs protein synthesis through RNA

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings RNA function in the actual synthesis of proteins Sites of protein synthesis are on ribosomes in the cytoplasm. Messenger RNA (mRNA) carries encoded message from the nucleus to the cytoplasm The flow of genetic information goes from DNA  RNA  protein (central dogma)

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure of Nucleic Acids Nucleic acids – Exist as polymers called polynucleotides (a) Polynucleotide, or nucleic acid

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Each polynucleotide – Consists of monomers called nucleotides

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nucleotide Monomers Are made up of nucleosides and phosphate groups Purine: Characterized by a five- membered ring fused to a six- membered ring. Examples - Adenine (A) - Guanine (G) Pyrimidine: Characterized by a six-membered ring made up of carbon and nitrogen atoms. Examples: - Cytosine (C) - Thymine (T); found only in DNA - Uracile (U); found only in RNA (c) Nucleoside components Figure 5.26

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nucleotide Polymers Nucleotide polymers – Are made up of nucleotides linked by the –OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next → phosphodiester linkages

59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The sequence of bases along a nucleotide polymer – Is unique for each gene

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The DNA Double Helix Cellular DNA molecules – Have two polynucleotides that spiral around an imaginary axis – Form a double helix

61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The DNA double helix – Consists of two antiparallel nucleotide strands

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The nitrogenous bases in DNA – Form hydrogen bonds in a complementary fashion (A with T only, and C with G only)