3.2

1. 3.2 The Structure and Function of Macromolecules

2. The Molecules of Life • Overview: • Another level in the hierarchy of biological organization is reached when small organic molecules are joined together • Atom ---> molecule --- macromolecule

3. 3.2.1 Organic Compounds • Most compounds important to life are organic, meaning that they contain carbon. • All of the macromolecules (lipids, carbohydrates, nucleic acids, and protein) are organic, carbon based, compounds.

4. Macromolecules • Most macromolecules are polymers, built from monomers • Four classes of life’s organic molecules are polymers • Carbohydrates • Proteins (monomer: amino acids) • Nucleic acids (monomer: nucleotides) • Lipids

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

6. 3.2.3 • Monosaccharides • Are the simplest sugars • Can be used for fuel (short term energy storage) • Can be converted into other organic molecules • Can be combined into polymers (disaccharides and polysaccharides)

7. Triose sugars(C3H6O3) Pentose sugars(C5H10O5) Hexose sugars(C6H12O6) H H H H O O O O C C C C H C OH H C OH H C OH H C OH H C OH H C OH HO C H HO C H Aldoses H H C OH H C OH HO C H H C OH H C OH H C OH Glyceraldehyde H C OH H C OH H Ribose H H Glucose Galactose H H H H C OH H C OH H C OH C O C O C O HO C H H C OH H C OH H C OH H C OH Ketoses H Dihydroxyacetone H C OH H C OH H C OH H Ribulose H Figure 5.3 Fructose • 3.2.3 Examples of monosaccharides

8. O H 1 C 6CH2OH 6CH2OH 2 CH2OH H C OH 5C H 5C O O 6 3 H O H H H H H 5 HO C H HOH H HOH 4 4C 1 C 1C 4C 4 1 OH H H H C OH O HO OH 3 2 OH OH 5 OH 2 C C 3 C 2C 3 OH H C H OH 6 H H OH OH H C OH H (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. Figure 5.4 • Monosaccharides • May be linear • Can form rings

9. 3.2.2 Recognize the structures of glucose and ribose Glucose

10. 3.2.3 Disaccharides • Consist of two monosaccharides • Are joined by a glycosidic linkage

11. (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 CH2OH CH2OH O O O O H H H H H H H H 1–4glycosidiclinkage HOH HOH HOH HOH 4 1 H H H H OH OH O H OH HO HO OH O H H H H OH OH OH OH H2O Glucose Maltose Glucose CH2OH CH2OH CH2OH CH2OH O O O O 1–2glycosidiclinkage H H H H H HOH HOH H 2 1 H OH H HO H HO H 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. (b) HO H O O HO CH2OH CH2OH OH H OH H H H OH OH H2O Glucose Sucrose Fructose 3.2.3 Disaccharide Examples: maltose, sucrose, and lactose and 3.2.5 the role of condensation reaction in the formation of a disaccharide *Lactose consists of glucose and galactose monomers

12. Polysaccharides • Polysaccharides • Are polymers of sugars • Serve many roles in organisms • Examples of roles are structural support and long-term energy storage

13. 3.2.3 Examples of Polysaccharides • Starch (a polymer of glucose used for energy storage in plants) • Chitin (a structural carbohydrate used in insect exoskeletons) • Cellulose (a polymer of glucose used for cell walls in plants) • Glycogen (a polymer of glucose used as long-term energy storage in animals)

14. Giycogen granules Mitochondria 0.5 m Glycogen (b) Glycogen: an animal polysaccharide 3.2.4- Uses of animal carbohydrates • Glucose is a 6-carbon sugar used as a reactant for cellular respiration • Lactose is a disaccharide present in the milk of mammals, as a sugar it delivers energy for cell respiration • Glycogen (a polymer of glucose) • Is the major storage form of glucose in animals

15. 3.2.4 Uses of Plant Carbohydrates • Cellulose • Is a polymer of glucose • Has different glycosidic linkages than starch • Makes up the cell wall in plants Fructose *is a monosaccharide used as fuel for fruits Sucrose *is a disaccharide used as fuel in many plants

16. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. Cellulose microfibrils in a plant cell wall Microfibril Cell walls  0.5 m Plant cells OH OH CH2OH CH2OH O O O O OH OH OH OH O O O O O OH CH2OH OH CH2OH Cellulose molecules CH2OH OH CH2OH OH O O O O OH OH OH OH Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. O O O O O OH CH2OH OH CH2OH CH2OH CH2OH OH OH O O O O OH OH OH OH O O O A cellulose molecule is an unbranched  glucose polymer. O O OH CH2OH OH CH2OH Figure 5.8 • Glucose monomer • Cellulose is a major component of the tough walls that enclose plant cells

17. Figure 5.9 • Cellulose is difficult to digest • Cows have microbes in their stomachs to facilitate this process

18. 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 • Chitin, another important structural polysaccharide • Is found in the exoskeleton of arthropods • Can be used as surgical thread

19. Lipids • 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

20. 3.2.2 Recognize a fatty acid • Vary in the length, number and locations of double bonds they contain • Consist of a long hydrocarbon chain with one end of the chain being a carboxylic acid (a carbon double bonded to an oxygen and a hydroxyl group)

21. General Formula: O (CH2)n CH3 O C Carboxyl group OH C OH H H H H H H H C C C C C C H H H H H H CH2 CH3 3.2.2 Recognize a fatty acid (notice the carboxylic acid group that will go through a condensation reaction with the –OH group from glycerol)

22. 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 3.2.5 The Synthesis and Breakdown of Polymers • Monomers form larger molecules by condensation reactions, called dehydration synthesis

23. 1 3 HO 4 2 H Hydrolysis adds a watermolecule, breaking a bond H2O 1 2 H HO 3 H HO (b) Hydrolysis of a polymer Figure 5.2B 3.2.5 The Synthesis and Breakdown of Polymers • Polymers can disassemble by • Hydrolysis (addition of water molecules)

24. 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

25. 3.2.5: glycerol + 3 fatty acids = triglyceride • Triglycerides are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids Glycerol

26. Glycerol H H H C C C H H OH OH OH Hydroxyl groups 3.2.5: glycerol + 3 fatty acids = triglyceride  Triglycerides are one of the most common types of lipids  Triglycerides consist of one molecule of glycerol bonded to three fatty acid molecules  Each fatty acid is linked to the glycerol molecule by an ester bond

27. O O C C OH OH H H H H H H H C C C C C C H H H H H H Another way to draw a fatty acid…. Can be drawn as:

28. H Hydroxyl group and carboxyl group react O H C OH O C OH Ester bond H C H OH C H OH C O H C H OH H C H OH C H Forming a monoglyceride: 3.2.5- a condensation reaction to form a triglyceride + H2O This is a condensation reaction

29. H O O O H C C C C O O H C O H C Fatty acid H Fatty acid Glycerol Fatty acid Ester bond A triglyceride: Can be drawn as:

30. H O H C OH O C OH H C H OH C H OH C O H C H OH H C H OH C H 3.2.5 To split these ester bonds and separate a fatty acid from glycerol (hydrolysis reaction) we need to add a molecule of water + H2O This is a hydrolysis reaction

31. Phospholipids • Have only two fatty acids • Have a phosphate group instead of a third fatty acid

32. + CH2 Choline N(CH3)3 CH2 O Phosphate Hydrophilic head – P O O O CH2 CH CH2 Glycerol O O C O C O Fatty acids Hydrophilic head Hydrophobic tails Hydrophobic tails (c) Phospholipid symbol (b) Space-filling model Figure 5.13 (a) Structural formula • Phospholipid structure • Consists of a hydrophilic “head” and hydrophobic “tails”

33. WATER Hydrophilic head WATER Hydrophobic tail • 3.2.6 Three functions of lipids • Phospholipids: • conform in a bilayer arrangement 1) Form the barrier that is the cell membrane

34. Human Adipose Tissue 3.2.6 More functions of lipids 1) Form membrane (phospholipid bilayer) 2) energy storage (animal adipose tissue or plant oils) 3) thermal insulation (adipose tissue, blubber) 4) electrical insulation (myelin sheaths of nerves)

35. 3.2.7 Compare the use of carbohydrates and lipids in energy storage. • Both are used for energy storage • Lipids store more energy per gram (almost twice as much)