Ch. 5 - Macromolecules

1. Ch. 5 - Macromolecules A Survey of the Organic Molecules That Make Up Life

2. A. Introduction • Macromolecules = large molecules (possibly made of 1000’s of atoms) formed when cells join together smaller organic molecules. • Four major classes of macromolecules: • Carbohydrates • Lipids • Proteins • Nucleic acids.

3. Most macromolecules are polymers • Three of the four classes of macromolecules form chainlike molecules called polymers. • Polymers consist of many similar or identical building blocks linked by covalent bonds. • The repeated units are small molecules called monomers.

4. Monomers are connected by covalent bonds via a condensation reaction or dehydration synthesis • One monomer provides a hydroxyl group and the other provides a hydrogen and together these form water. • This process requires energy and is aided by enzymes.

5. The covalent bonds connecting monomers in a polymer are broken apart by hydrolysis with the addition of water. • In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. • Hydrolysis reactions dominate the digestive process, guided by specific enzymes.

6. Hydrolysis Song (to the tune of “My Boyfriend’s Back”) • The H’s are back and so are the O’s • Hey-Nah, Hey Nah, HYDROLYSIS • The starch turns to glucose and proteins to aminos • Hey-Nah, Hey Nah, HYDROLYSIS • Hey, it’s DIGESTION in the body • Hey, it’s how we SPLIT the macromole(cules) • The H’s are back and so are the O’s • Hey-Nah, Hey Nah, HYDROLYSIS

7. Review Molecule B • What reaction does the diagram to the right represent? • Which molecule represents a monomer? • Which molecules represent polymers? • What is the source of the H and OH on molecules C and D? Molecule A hydrolysis Molecule D Molecule C Molecule D Molecules A & C H2O/water

8. B. Carbohydrates • Carbohydrates are organic molecules made from the elements C, H and O. • All carbohydrates havea 2:1 ratio between hydrogen and oxygen. • Thesimplest carbohydrates are monosaccharides or simple sugars (1 ring). • Disaccharides, double sugars (2 ring), consist of two monosaccharides joined by dehydration synthesis. • Polysaccharides are polymers (many rings) of monosaccharides joined together. HYDRATE refers to WATER = H2O (2H:1O)

9. Sugars, the smallest carbohydrates serve as a source of energy • Monosaccharides, particularly glucose, are a major fuel for cellular work. • While often drawn as a linear skeleton, in aqueous solutions, monosaccharides form rings.

10. Sugars, the smallest carbohydrates serve as a source of energy • Monosaccharides generally have molecular formulas that are some multiple of CH2O. • For example, glucose has the formula C6H12O6. • Most names for sugars end in -ose. • Monosaccharides have a carbonyl group and multiple hydroxyl groups. • Glucose, an aldehyde, and fructose, a ketone, are structural isomers. • Glucose and galactose are both aldehydes but one carbon has the “H” and “OH” switched.

11. If carbohydrates have multiple hydroxyl groups, will they tend to be hydrophilic or hydrophobic? Why? • Hydrophilic, because of the polar covalent bonds between the O and H of the hydroxyl groups.

12. Monosaccharides are also classified by the number of carbons in the backbone. • Glucose and other six (6) carbon sugars are hexoses. • Five (5) carbon backbones are pentoses • Three (3) carbon sugars are trioses.

14. Two monosaccharides can join with a glycosidic linkage to form a dissaccharidevia dehydration synthesis. • Maltose, malt sugar, is formed by joining two glucose molecules. • Sucrose, table sugar, is formed by joining glucose and fructose and is the major transport form of sugars in plants. • Lactose, milk sugar, is formed by joining glucose and galactose. Several people lack the enzyme to digest this sugar and are “lactose intolerant”.

15. Dehydration Synthesis:Glucose +Glucose Maltose +Water

16. Use what you know to figure out the molecular formula for maltose. • If the molecular formula for glucose is C6H12O6 and 2 glucose molecules are needed to synthesize one maltose molecule through dehydration synthesis, what is the molecular formula for maltose? C12H22O11 C6H12O6 + H2O + C6H12O6

17. Dehydration synthesis of sucrose

18. If glucose and fructose are isomers, then what is the molecular formula for sucrose? • Same as maltose: C12 H22 O11

19. Polysaccharides, the polymers of sugars, have storage and structural roles • Polysaccharides are polymers of hundreds to thousands of monosaccharides joined by glycosidic linkages. • Functions of polysaccharides: • energy storage macromolecule that is hydrolyzed as needed. • building materials for the cell or whole organism.

20. Plant Polysaccharides include starch and cellulose… • Plants store starch within plastids, including chloroplasts. • Plants can store surplus glucose in starch and withdraw it when needed for energy or carbon. • Animals that feed on plants, especially parts rich in starch, can also access this starch to support their own metabolism.

21. Starch is a storage polysaccharide composed entirely of glucose monomers. • Most monomers are joined by 1-4 linkages between the glucose molecules. • One unbranched form of starch, amylose, forms a helix. • Branched forms, like amylopectin, are more complex.

22. While polysaccharides can be built from a variety of monosaccharides, glucose is the primary monomer used in polysaccharides. • One key difference among polysaccharides develops from 2 possible ring structures of glucose. • These two ring forms differ in whether the hydroxyl group attached to the number 1 carbon is fixed above (beta glucose) or below (alpha glucose) the ring plane.

23. Starch is a polysaccharide of alpha glucose monomers.

24. Structural polysaccharides form strong building materials. • Cellulose is a major component of the tough wall of plant cells. • Cellulose is also a polymer of glucose monomers, but using beta rings.

26. The enzymes that digest starch cannot hydrolyze the beta linkages in cellulose. • Cellulose in our food passes through the digestive tract and is eliminated in feces as “insoluble fiber”. • Some microbes can digest cellulose to its glucose monomers through the use of cellulase enzymes. • Many eukaryotic herbivores, like cows and termites, have symbiotic relationships with cellulolytic microbes, allowing them access to this rich source of energy.

27. Animals also store glucose in a polysaccharide called glycogen. • Glycogen is highly branched. • Humans and other vertebrates store glycogen in the liver and muscles but only have about a one day supply. Insert Fig. 5.6b - glycogen

28. Another important structural polysaccharide is chitin, used in the exoskeletons of arthropods (including insects, spiders, and crustaceans). • Chitin is similar to cellulose, except that it contains a nitrogen-containing appendage on each glucose. • Chitin also forms the structural support for the cell walls of many fungi.

29. Try to make a word map for carbohydrates. category Organic macromolecules example Contains C, H, & O with 2 H: 1 O ratio Is like. . . Properties are . . . Often seen with ring structure Is like. . . Properties are . . . carbohydrates Target word Is like. . . Properties are . . . Hydrophilic, can join together through dehydration synthesis monosaccharides example disaccharides example polysaccharides

30. Match the term with its description or definition. • Used in insect exoskeletons & fungus cell walls • Coiled structure • Used in plant cell walls • Energy storage molecule in plants • Energy storage molecule in animals • Contains alpha 1-4 glycosidic linkages • Chitin • Cellulose • Glycogen • Starch/ Amylose A D, C B D C D, C

31. C. Lipids • Lipids are highly diverse in form and function. • Examples: fats, waxes, oils, steroids • The unifying feature of lipids is that they can have little or no affinity for water. • This is because their structures are dominated by nonpolar covalent bonds. • Lipids have C, H, and O but a H : O ratio greater than 2:1.

32. Fats are one example of a lipid. • Fats are large molecules assembled from smaller molecules by dehydration reactions. • A fat is constructed from two kinds of smaller molecules, glycerol and fatty acids. • One glycerol + 3 fatty acids combine to form a fat molecule + 3 water molecules. • Fats can store large amounts of energy.

33. • Glycerol (an alcohol) consists of a three carbon skeleton with a hydroxyl group (OH) attached to each…ho-ho-ho… •A fatty acid consists of a carboxyl group (COOH) attached to a long carbon skeleton, often 16 to 18 carbons long. http://appadvice.com/appnn/2010/07/dear-santa-ipad

34. The many nonpolar C-H bonds in the long hydrocarbon skeleton make fats hydrophobic. • In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol.

35. The three fatty acids in a fat can be the same or different. • Fatty acids may vary in length (number of carbons) and in the numberand locations of double bonds. • If there are no carbon-carbon double bonds, then the molecule is a saturated fatty acid- a hydrogen at every possible position. • Straight chain

36. If there are one or more carbon-carbon double bonds, then the molecule is an unsaturated fatty acid - formed by the removal of hydrogen atoms from the carbon skeleton. • Unsaturated fatty acids have a kink (bend)wherever there is a double bond. \

37. Saturated fats . . . • contain saturatedfattyacids • are solid at room temperature • make up most animal fats • A diet rich in saturated fats may contribute to cardiovascular disease (atherosclerosis) through plaque deposits. • Unsaturated fats. . . • Contain unsaturatedfattyacids • are liquid are room temperature (known as oils) • The kinks provided by the double bonds prevent the molecules from packing tightly together. • Are found in plant and fish fats

38. Match the term with its description or definition. • Contains one or more carbon-carbon double bonds • Contains carboxyl group • Fat mostly made by animals • Fat made by fish and plants • Solid at room temperature • Liquid at room temperature • Bent molecule that releases H ions • Straight acidic molecule • Saturated fatty acid • Unsaturated fatty acid • Saturated fat • Unsaturated fat B,D A,B C D C, A D, B B A

39. FUNCTIONS of FATS • Major function = energy storage • A gram of fat stores more than twice as much energy as a gram of a polysaccharide. • Plants use starch for energy storage when mobility is not a concern but use oils when dispersal and packing is important, as in seeds. • Humans and other mammals store fats as long-term energy reserves in adipose cells. • Cushioning for vital organs • Insulation • This subcutaneous layer is especially thick in whales, seals, and most other marine mammals.

40. Phospholipids are major components of cell membranes • Phospholipids have two fatty acids attached to glycerol and a phosphate group at the thirdposition. • The phosphate group carries a negative charge. • Having a charge on one side of the phospholipid (hydrophilic) and no charge on the other side (hydrophobic) makes this molecule have different personalities on either end. • This “double” personality is key to how the structure of a membrane is adaptive to its function of transport for the cell.

41. The interaction of phospholipids with water is complex. • The fatty acid tails are hydrophobic (water fearing), but the phosphate group and its attachments form a hydrophilic (water loving) head.

42. At the surface of a cell, phospholipids are arranged as a bilayer. • Again, the hydrophilic heads are on the outside in contact with the aqueous solution and the hydrophobic tails form the core. • The phospholipid bilayer forms a barrier between the cell and the external environment. • They are the major component of membranes. Hydrophilic heads Hydrophobic tails Hydrophilic heads

43. Phospholipid Song (to the tune of “Oh My Darling”) Oh, my lipid Phos-pho-lipid Oh, my lipid ‘Round the cell Hy-dro-pho-bic Fat-ty a-cids Fear the water they re-pel Oh, my lipid Phos-pho-lipid Oh, my lipid ‘Round the cell Hy-dro-phil-ic Are the phos-phates Touching water, there they dwell Oh, my lipid Phos-pho-lipid Oh, my lipid ‘Round the cell You are made of Fat-ty a-cids And a phos-phate head as well. Add the backbone Made of glyc’rol Add the backbone To join three All together = Phospholipids Make the cells of you and me

44. Steroids include cholesterol and certain hormones • Steroids are lipids with a carbon skeleton consisting of four fused carbon rings. • Different steroids are created by varying functional groups attached to the rings.

45. Cholesterol, an important steroid, is a component in animal cell membranes. • Cholesterol is also the precursor from which all other steroids are synthesized. • Many of these other steroids are hormones, including the vertebrate sex hormones. • While cholesterol is clearly an essential molecule, high levels of cholesterol in the blood may contribute to cardiovascular disease.

46. Try to make a word map for lipids. category Organic macromolecules Contains C, H, & O with H:O ratio much greater than 2:1 Is like. . . Properties are . . . hydrophobic Is like. . . Properties are . . . lipids Target word Is like. . . Properties are . . . Many nonpolar C-H bonds FATS example PHOSPHOLIPIDS example STEROIDS example

47. Lipids review • True or False: All lipids are fats. • What are the three components that are attached to a glycerol molecule in a phospholipid? • Sketch a diagram of a phospholipid. Where are these found in a cell? • Describe the structure of a steroid. • Why is cholesterol such an important steroid? Phosphate, 2 fatty acids Cell membrane 4 fused carbon rings Part of cell membranes, precursor to steroid hormones, too much in blood can cause heart disease

48. Proteins • Proteins are instrumental in about everything that an organism does. • These functions include structural support, storage, transport of other substances, intercellular signaling, movement, and defense against foreign substances. • Almost all enzymes in a cell are proteins. These regulate metabolism by selectively accelerating chemical reactions. • Humans have tens of thousands of different proteins, each with its own structure and function.

49. Proteins are the most structurally complex molecules known. • Each type of protein has a complex three-dimensional shape or conformation. • All protein polymers are constructed from the same set of 20 monomers, called amino acids. • Polymers of proteins are called polypeptides. • A protein consists of one or more polypeptides folded and coiled into a specific conformation.

50. R O H C N C OH H H Basic amino acid A polypeptide is a polymer of amino acids connected in a specific sequence • Amino acids consist of four components attached to a central carbon. • These components include a hydrogen atom, a carboxyl group, an amino group, and a variable R group (or side chain). • Differences in R groups produce the 20 different amino acids.