Chapter 5

1. Chapter 5 The Structure and Function of Macromolecules

2. Macromolecules • Macromolecules • Are large molecules composed of smaller molecules • Four major classes of macromolecules • Carbohydrates • Lipids • Proteins • Nucleic Acids

3. Polymers and Monomers • Most macromolecules are polymers, built from monomers • A polymer • Is a long molecule consisting of many similar building blocks called monomers • An immense variety of polymers can be built from a small set of monomers

4. Polymers and Monomers • Three of the classes of life’s organic molecules are polymers • Carbohydrates • Proteins • Nucleic acids

5. 1 HO H 3 2 H HO Unlinked monomer Short polymer Dehydration removes a watermolecule, forming a new bond H2O 1 2 3 4 HO H Longer polymer (a) Dehydration reaction in the synthesis of a polymer Figure 5.2A The Synthesis and Breakdown of Polymers • Monomers link together to form polymers by condensation synthesis, a dehydration reaction • A water molecule is removed

6. The Synthesis and Breakdown of Polymers • Polymers break down to their component monomers by hydrolysis • A water molecule is added 1 3 HO 4 2 H Hydrolysis adds a watermolecule, breaking a bond H2O Figure 5.2B 1 2 H HO 3 H HO (b) Hydrolysis of a polymer

7. Carbohydrates • Serve as fuel and building material • Include both sugars and their polymers • Monosaccharides • Disaccharides • Polysaccharides

8. Monosaccharides • Monosaccharides • Are the simplest sugars • Can be used for fuel • Can be converted into other organic molecules • Can be combined into polymers • May be linear or may form rings

9. Disaccharides • Disaccharides • Consist of two monosaccharides joined by condensation synthesis

10. Polysaccharides • Polysaccharides • Are polymers of sugars • Serve many roles in organisms

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

12. Mitochondria Giycogen granules 0.5 m Glycogen Figure 5.6 (b) Glycogen: an animal polysaccharide Storage Polysaccharides • Glycogen • Is a polymer consisting of glucose monomers • Is the major storage form of glucose in animals

13. H O CH2OH CH2OH C OH OH H C H O O H H H HO H OH OH C H 4 4 1 H H HO OH HO OH H H C OH OH OH H H C H OH  glucose C  glucose H (a)  and  glucose ring structures CH2OH CH2OH CH2OH CH2OH O O O O OH OH OH OH 1 4 4 4 1 1 1 HO O O O O OH OH OH OH (b) Starch: 1– 4 linkage of  glucose monomers OH OH CH2OH CH2OH O O OH OH O OH OH O HO OH 4 O 1 O O CH2OH CH2OH OH OH (c) Cellulose: 1– 4 linkage of  glucose monomers Figure 5.7 A–C Structural Polysaccharides • Cellulose • Is a polymer consisting of glucose monomers • Is the major component of plant cell walls • Is difficult for animals to digest

14. CH2OH O OH H H OH H H H NH O C CH3 OH (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. (a) The structure of the chitin monomer. Figure 5.10 A–C Structural Polysaccharides • Chitin • Is found in the exoskeleton of arthropods • Can be used as surgical thread

15. Lipids • Lipids • Are the one class of large biological molecules that do not consist of polymers • are a diverse group of molecules that share the common trait of being hydrophobic • Include • Fats • Phospholipids • Steroids

16. Fats • Fats • Are constructed from two types of smaller molecules, glycerol (a 3 carbon alcohol) and three fatty acids (a 16-18 carbon skeleton with a carboxyl group) • Functions of fats • energy storage, insulation, cushioning

17. Fatty Acids • Fatty acids • Vary in the length and number and locations of double bonds they contain • Saturated fatty acids • Have no double bonds and therefore have the maximum number of hydrogen atoms possible • Unsaturated fatty acids • Have one or more double bonds and therefore have less than the maximum number of hydrogen atoms possible

18. 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

19. Phospholipids • Phospholipids • Are constructed from one glycerol (a 3 carbon alcohol) plus two fatty acids (a 16-18 carbon skeleton with a carboxyl group) and a phosphate group • Functions of phospholipids • Main component of cell membranes

20. Phospholipid Structure • Are amphipathic because they contain both polar and nonpolar regions • Consists of a hydrophilic “head” and hydrophobic “tails”

21. WATER Hydrophilic head WATER Hydrophobic tail Figure 5.14 Phospholipid Structure • The amphipathic nature of phospholipids • Results in a bilayer arrangement found in cell membranes

22. Steroids • Steroids • Are lipids consisting of four fused carbon rings • Functions of steroids • One steroid, cholesterol, is an important part of cell membranes • Steroid hormones are based on the cholesterol molecule and control sex and growth characteristics Cholesterol

23. Proteins • Proteins • Have many structures, resulting in a wide range of functions • Each protein consists of one or more polypeptides • Polypeptides • Are polymers of amino acid monomers

24. Table 5.1 An Overview of Protein Functions

25.  carbon R O H C C N OH H H Amino group Carboxyl group Amino Acid Monomers • Amino acids • Consist of a central carbon atom bonded to • Hydrogen atom • Carboxyl group • Amino group • Variable R group

26. Figure 5.17The 20 amino acids of proteins • Differ in their properties due to differing R groups • All the wide variety of proteins are made simply by varying the number and order of these twenty amino acids

27. Peptidebond OH SH CH2 CH2 CH2 H H H C C N C H C H C C OH OH N N DESMOSOMES H O H O H O (a) H2O OH DESMOSOMES DESMOSOMES Side chains SH OH Peptidebond CH2 CH2 CH2 H H H N OH C H C C C N C C N Backbone H H O O H O Amino end(N-terminus) Carboxyl end(C-terminus) Figure 5.18 (b) Amino Acid Polymers • Amino acids • Are linked by peptide bonds formed by condensation synthesis OH

28. Protein Conformation and Function • A protein’s specific conformation, or shape • Determines how it functions • There are four levels of protein structure • Primary structure • Secondary structure • Tertiary structure • Quaternary structure

29. Protein Structure • Primary level of organization • Sequence of amino acids • Numbered from the amino end • Each protein has a unique combination of amino acids

30. Protein Structure • Secondary level of organization • Is the folding or coiling of the polypeptide into a repeating configuration caused by Hydrogen bonds between the amine and carbonyl groups of amino acids • Includes the  helix and the  pleated sheet

31. Protein Structure • Tertiary level of organization • Is the overall three-dimensional shape of a polypeptide • Results from interactions between amino acids and R groups • Stabilized by • Disulfide bridges • Ionic bonds • H bonds • Hydrophobic and van der Waals interactions

32. Protein Structure • Quaternary level of organization • Is the overall protein structure that results from the aggregation of two or more polypeptide subunits Collagen Hemoglobin

33. Primary - number, order of amino acids Secondary - coil, pleated sheet Tertiary - globular, 3-dimensional Quarternary - multiple protein chains 4 Levels of Protein Structure

34. Protein conformation and function • Protein conformation and function • Depends on the physical and chemical conditions of the protein’s environment, eg. Temperature and pH • Denaturation • Is when a protein unravels and loses its native conformation Denaturation Normal protein Denatured protein Figure 5.22

35. Nucleic Acids • Nucleic Acids • Are polymers of nucleotide monomers • There are two types of nucleic acids • DNA (Deoxyribonucleic acid) • RNA (Ribonucleic acid) • The function of nucleic acids is to store and transmit hereditary information • DNA  RNA  Polypeptides

36. Nucleotide Structure and Function • Each nucleotide consists of 3 parts: • Nitrogenous base • Pyrimidine • Purine • 5 carbon sugar • Ribose • Deoxyribose • Phosphate group

37. 5’ end 5’C O 3’C O O 5’C O 3’C 3’ end OH Figure 5.26 Nucleotide Polymers • Nucleotide polymers • Are made up of nucleotides linked by condensation synthesis • the–OH group on the 3´ carbon of one nucleotide bonds to the phosphate on the 5´ carbon on the next • The sequence of bases along a nucleotide polymer • Is unique for each gene

38. 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 • DNA • double strand of nucleotides • twisted into a double helix • stores information for the synthesis of specific proteins through RNA

39. Complementary Base Pairs in DNA • Hydrogen bonds between the nitrogenous bases in the 2 DNA strands hold the 2 strands together • Purines always bond to pyrimidines (A with T only, and C with G only)

40. 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 RNA • RNA • Single strand of nucleotides • Contains A, U, C, G • transcribes information from DNA, and uses that information for the synthesis of specific proteins