1. Overview: The Molecules of Life 4 Classes of organic molecules make up living things: 1.Carbohydrates 2.Lipids 3.Proteins 4.Nucleic acids

2. Overview: The Molecules of Life Cells use a limited number of building blocks (40 to 50) to build thousands of different organic molecules. Most of the molecules are very large - macromolecules – 1000s of covalently connected atoms. Cells build macromolecules from smaller building blocks Emergent properties and correlation of structure to function are common themes in this chapter.

3. Concept 5.1: Macromolecules are polymers, built from monomers A polymer - long molecule consisting of many similar small building blocks called monomers Three of the four classes of life’s organic molecules are polymers: – Carbohydrates – Proteins – Nucleic acids Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

4. Did you really understand that polymer/monomer stuff? Let’s think of some analogies that will help us visualize the relationship between polymers and monomers: POLYMERS AND MONOMERS ARE LIKE...

5. MAKE Condensation reaction or dehydration reaction - two monomers covalently bond together & one molecule of water is formed Enzymes speed up the dehydration process The chemical reaction which makes or breaks down a polymer is basically the same for all organic compounds. Animation: Polymers Animation: Polymers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Fig. 5-2a Dehydration removes a water molecule, forming a new bond Short polymerUnlinked monomer Longer polymer Dehydration reaction in the synthesis of a polymer HO H2OH2O H H H 4 3 2 1 1 2 3 (a)

7. BREAK Polymers are disassembled to monomers by hydrolysis, essentially the reverse of dehydration reaction A molecule of water is required for each bond that is broken Enzymes speed up the hydrolysis process Animation: Polymers Animation: Polymers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Fig. 5-2b Hydrolysis adds a water molecule, breaking a bond Hydrolysis of a polymer HO H2OH2O H H H 3 2 1 1 23 4 (b)

9. Fig. 5-2 Short polymer HO 123H H Unlinked monomer Dehydration removes a water molecule, forming a new bond HO H2OH2O H 1 2 3 4 Longer polymer (a) Dehydration reaction in the synthesis of a polymer HO 1 2 3 4 H H2OH2O Hydrolysis adds a water molecule, breaking a bond HO H H 1 2 3 (b) Hydrolysis of a polymer

10. TEST YOURSELF Suppose you eat a serving of green beans. What reactions must occur for the amino acid monomers in the protein of the beans to be converted to proteins in your body? These reactions would occur too slowly at cellular temperatures to keep you alive. Name the molecules that speed up chemical reactions such as condensation and hydrolysis.

11. Concept 5.2: Carbohydrates serve as fuel and building material Carbohydrates are sugars and polymers of sugars such as starch and cellulose; most sugar names end in -ose Composed of C, H, O; ratio of H to O is 2:1 Classified by number of monomers they contain : – Monosaccharide – one monomer – Disaccharide – two monomers – Polysaccharide – many monomers

12. SIMPLE SUGARS: MONOSACCHARIDES molecular formula is usually multiple of CH 2 O Glucose (C 6 H 12 O 6 ) is most common monosaccharide. Monosaccharides are classified by 1.location of carbonyl group (aldose or ketose) 2.number of carbons in carbon skeleton 3.multiple hydroxyl groups 4.there may be chiral carbons

13. Fig. 5-3 Dihydroxyacetone Ribulose Ketoses Aldoses Fructose Glyceraldehyde Ribose Glucose Galactose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 ) Trioses (C 3 H 6 O 3 )

14. Fig. 5-3a Aldoses Glyceraldehyde Ribose GlucoseGalactose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 )Trioses (C 3 H 6 O 3 )

15. Fig. 5-3b Ketoses Dihydroxyacetone Ribulose Fructose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 )Trioses (C 3 H 6 O 3 )

16. Glucose and galactose: Glucose and fructose: Fructose and galactose: NOTE: glucose, fructose, and galactose are isomers: C 6 H 12 O 6

17. Fig. 5-3 Dihydroxyacetone Ribulose Ketoses Aldoses Fructose Glyceraldehyde Ribose Glucose Galactose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 ) Trioses (C 3 H 6 O 3 )

18. Fig. 5-4 (a) Linear and ring forms (b) Abbreviated ring structure Though often drawn as linear skeletons, in aqueous solutions many sugars form rings Note that the closing of the ring involves the carbonyl group

19. Fig. 5-4a (a) Linear and ring forms

20. Fig. 5-4b (b) Abbreviated ring structure Carbons are numbered clockwise from the oxygen in the ring.

21. Monosaccharides are major nutrients for cells: (1) source of energy (2) carbon skeletons for building other organic molecules Glucose – “blood sugar”; the major fuel used by most cells; common building block for structural sugars Fructose - fruit sugar Galactose - a monomer found in milk sugar

22. Disaccharides - dehydration reaction joins two monosaccharides The new covalent bond between the two monosaccharides is called a glycosidic linkage Animation: Disaccharides Animation: Disaccharides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings DOUBLE SUGARS: DISACCHARIDES

23. Fig. 5-5 (b) Dehydration reaction in the synthesis of sucrose GlucoseFructose Sucrose MaltoseGlucose (a) Dehydration reaction in the synthesis of maltose 1–4 glycosidic linkage 1–2 glycosidic linkage

24. COMMON DISSACHARIDES Sucrose – glucose + fructose; produced by plants; table sugar is generally produced from sugar cane or sugar beets Lactose – glucose + galactose; milk sugar; lactose intolerant individuals produce little to none of enzyme needed to break the glycosidic linkage between glucose and galactose Maltose – glucose + glucose; malt sugar; found in germinating seeds and produced during beer brewing

25. Note on plants and sugars Plants produce the sugar glucose as a product of photosynthesis Plants transport sugar in their sap as sucrose. Plants store sugar in polymers of glucose called starch.

26. CAN YOU DETERMINE THE MOLECULAR FORMULAS FOR SUCROSE, MALTOSE, AND LACTOSE?

27. SUGAR POLYMERS: POLYSACCHARIDES Polysaccharides, polymers of sugars, have storage and structural roles The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

28. Storage Polysaccharides: STARCH Starch, storage polysaccharide of plants, consists entirely of glucose monomers Plants store surplus starch as granules within chloroplasts and other plastids Plant “banks” glucose while conditions for photosynthesis are good, then makes “withdrawals” by hydrolyzing starch when glucose is needed.

29. Storage Polysaccharides: STARCH Most animals produce the enzymes needed to break down starch The major sources of starch in our diet come from potato tubers and grains like rice, wheat, and corn

30. Glycogen is a storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells When blood sugar drops glycogen is hydrolyzed to glucose and is transported into the blood. Humans have only about a 24 hour supply of glycogen Storage Polysaccharides: GLYCOGEN

31. Fig. 5-6 (b) Glycogen: an animal polysaccharide Starch Glycogen Amylose Chloroplast (a) Starch: a plant polysaccharide Amylopectin Mitochondria Glycogen granules 0.5 µm 1 µm

32. If both starch and glycogen are polymers of glucose, how do they differ? STARCH: glucose monomers joined by 1-4 linkage – carbon 1 on one monomer is joined to carbon 4 on the next monomer – Angle of the bonds creates a helical (sprial) molecule – Amylose, the simplest starch, has not branches; amylopectin is branched GLYCOGEN – extensively branched

33. Structural Polysaccharides: CELLULOSE Cellulose is a major component of the tough wall of plant cells; it is the most abundant organic compound on Earth! Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ The difference is based on two ring forms for glucose: alpha (  ) and beta (  ) Animation: Polysaccharides Animation: Polysaccharides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34. Fig. 5-7 (a) α and β glucose ring structures α Glucose β Glucose (b) Starch: 1–4 linkage of α glucose monomers(b) Cellulose: 1–4 linkage of β glucose monomers

35. Fig. 5-7a (a) α and β glucose ring structures α Glucose β Glucose

36. Fig. 5-7bc (b) Starch: 1–4 linkage of α glucose monomers (c) Cellulose: 1–4 linkage of β glucose monomers

37. Polymers with  glucose are helical Polymers with  glucose are straight In straight structures, H atoms on one strand can hydrogen bond with OH groups on other strands Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

38. Fig. 5-8 b Glucose monomer Cellulose molecules Microfibril Cellulose microfibrils in a plant cell wall 0.5 µm 10 µm Cell walls

39. Enzymes that digest starch by hydrolyzing  linkages can’t hydrolyze  linkages in cellulose NO ANIMAL CAN MAKE THE ENZYME TO HYDROLYZE  LINKAGES Cellulose in human food passes through the digestive tract as insoluble fiber; abrades lining of digestive tract which stimulates mucus production and eases passage of feces through the tract; IF you don’t get enough fiber in your diet, you may become constipated! SO WHY CAN’T WE END HUNGER BY EATING CELLULOSE??! A POLYMER OF GLUCOSE! MOST ABUNDANT ORGANIC COMPOUND ON THE PLANET!

40. Fungi, some bacteria, and some protists do produce the enzymes to digest cellulose; their role as decomposers is critical to the recycling of matter in the biosphere Many herbivores, from cows to termites, have symbiotic relationships with these microbes Speculate! Does Checkers or Gus have gut flora that break down cellulose? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

41. Fig. 5-9 What would happen if a cow was given enough antibiotics to kill all the prokaryotes in its gut? Please ask me about what happens to the grass the cow eats!!!!!!!

42. Found in the exoskeleton of arthropods and the cell walls of fungi Structurally similar to cellulose but has a nitrogen containing group attached to glucose Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chitin, a structural polysaccharide

43. Fig. 5-10 The structure of the chitin monomer. (a) (b) (c) Chitin forms the exoskeleton of arthropods. Chitin is used to make a strong and flexible surgical thread.