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Chapter 5 The Structure and Function of Macromolecules CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES Section A: Polymer principles 1. Most macromolecules are polymers 2. An immense variety of polymers can be built from a small set of monomers Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Introduction Cells join smaller organic molecules together to form larger molecules. Macromolecules The four major classes: carbohydrates, lipids, proteins, and nucleic acids. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Most macromolecules are polymers Polymers consist of many similar or identical building blocks linked by covalent bonds. The repeated units are small molecules called monomers. Some monomers have other functions of their own. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Monomer A building block of a polymer. Condensation Synthesis or Dehydration Synthesis The chemical reaction that joins monomers into polymers. Covalent bonds are formed by the removal of a water molecule between the monomers. Building Polymers: Fig. 5.2a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Disassembling Polymers: via hydrolysis. “to break with water” Hydrolysis reactions dominate the digestive process, guided by specific enzymes. Fig. 5.2b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Hydrolysis Reverse of condensation synthesis. Hydro- water Lysis - to split Breaks polymers into monomers by adding water. Four Main Types Of Macromolecules Carbohydrates Lipids Protein Nucleic acids Carbohydrates Used for fuel, building materials, and receptors. Made of C,H,O General formula is CH2O C:O ratio is 1:1 Types Of Carbohydrates Monosaccharides Disaccharides Polysaccharides Monosaccharides Mono - single Saccharide - sugar Simple sugars. 3 to 7 carbons. Can be in linear or ring forms. functions Fuel for cells—esp. glucose Build other macromolecules (rearrangement) Fig. 5.4 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Monosaccharides Can be “Aldoses” or “Ketoses” depending on the location of the carbonyl group. Examples Glucose Galactose Ribose (hexoses) Fructose (pentose) - OSE Word ending common for many carbohydrates. Disaccharides Formed in a dehydration reaction Covalent bond called a “glycosidic linkage” Examples Maltose = glucose + glucose Lactose = glucose + galactose Milk sugar Sucrose Table = glucose + fructose sugar Major transport form of sugar in plants Fig. 5.5a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Polysaccharides Many joined simple sugars. Used for storage or structure. Examples: Starch-storage in plants Cellulose-plant cell wall; structure Glycogen-animals; energy reserve Chitin-Nitrogen containing;structural; arthropod shell; fungi cell wall; Glucose has 2 possible ring structures. Hydroxyl group, attached to the number 1, carbon may be fixed above (beta glucose) or below (alpha glucose) the ring plane. Fig. 5.7a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings a glucose and b glucose Starch of 1-4 linkages of a glucose. Linkage makes the molecule form a helix. Fuel storage in plants. Made a glucose Cellulose of 1-4 linkages of b glucose. Linkage makes the molecule form a straight line. Made This allows H atoms on one strand to form hydrogen bonds with OH groups on other strands. Groups of polymers form strong strands, microfibrils, that are basic building material for plants (and humans). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings b glucose Comment Most organisms can digest starch (1- 4 a linkage), but very few can digest cellulose (1- 4 b linkage). Another example of the link between structure and function. Glycogen “Animal starch” Similar to starch, but has more 1-6 linkages or branches. Found in the liver and muscle cells. Starch Glycogen Chitin Structural polysaccharide Exoskeletons of arthropods (including insects, spiders, and crustaceans). Also fungi cell wall. Similar to cellulose, but,contains a nitrogen appendage. Pure chitin is leathery, but the addition of calcium carbonate hardens the chitin. Fig. 5.9 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Lipids--Introduction Not polymers. Hydrophobic molecules. Structures dominated by nonpolar covalent bonds. Made of C,H,O No general formula. C:O ratio is very high in C. Highly diverse in form and function. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 1. Fats Syn. From Glycerol + fatty acid(s) Glycerol: contains hydroxyl (-OH) group Fatty Acid: A long carbon chain (12-18 C) with a -COOH (acid) on one end and a -CH3 at the other. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Triglyceride/triaclyglycero 3 fatty acids +glycerol Fig. 5.10b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings The 3 Fatty Acids in a FAT can be the Same or Different Variations: Length of chain (# of carbons). # of double bonds Locations of double bonds. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Saturated vs. Unsaturated Fats Saturated Fatty acids No double bonds (between carbons). Straight chains Found in animals Solid at room temp. Factor in atherosclerosis. Unsaturated fatty acids One or more double bonds. Structure has a kink at double bond(s). Plants, fish. Liquid at room temp. Commonly called “oil” Fig. 5.11b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fats with saturated fatty acids are saturated fats. Most animal fats are saturated. Saturated fats are solid at room temperature. A diet rich in saturated fats may contribute to cardiovascular disease (atherosclerosis) through plaque deposits. Fats with unsaturated fatty acids are unsaturated fats. Plant and fish fats, known as oils, are liquid are room temperature. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fat- Functions 1. Long-term Energy storage, esp. in animals- (9kcal/g) : twice as much as carb. It’s more compact than starch or glycogen Cushions Insylates Acid Fat REVIEW: Saturated Fats Unsaturated Fats Saturated - no double bonds. Unsaturated - one or more C=C bonds. Can accept more Hydrogens. Double bonds cause “kinks” in the molecule’s shape. Question ? Which has more energy, a kg of fat or a kg of starch? Fat - there are more C-H bonds which provide more energy per mass. Which is which? Properties? 2. Phospholipids Similar to fats, but have only two fatty acids. The third -OH of glycerol is joined to a phosphate containing molecule (has a negative charge). Be able to draw;labelpolar and nonpolar ends The Result Is… Phospholipids have a hydrophylic head tail, but a hydrophobic tail. Self-assemble into micelles or bilayers, an important part of cell membranes. 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 from the core. The phospholipid bilayer forms a barrier between the cell and the external environment. They are the major component of membranes. Fig. 5.12b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 3. Steroids Lipids with four fused rings. Examples: cholesterol Steroid (sex hormones) Functions off Cholesterol in animals Only in animals. Component in animal cell membranes-stability & insulation. Precursor from which all other steroids are synthesized. Many are hormones, including the vertebrate sex hormones. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Introduction 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. Proteins are the overwhelming enzymes in a cell and regulate metabolism by selectively accelerating chemical reactions. Copyright Humans have tens of thousands © 2002 Pearson Education, Inc., publishing as Benjamin Cummings of Proteins Half the weight of a dry cell. Made of C,H,O,N, and sometimes S. No general formula. Polymer of amino acids Types Of Proteins Enzymes Movie Structure Storage Transport Hormones Receptors Contractile motor Defense & Proteins Polypeptide Polymers of Amino Acids peptide bonds. Protein: One or more polypeptides folded and coiled into specific conformations. Amino Acids Asymmetrical -COOH Carbon-with: (acid) NH2 (amino) H R (side group) Different R groups 20 different kinds: Determines the physical & chemical properties of the amino acid. Nonpolar Polar Electrically Charged Amino Acids Amino Acids Polypeptides Dehydration synthesis between the carboxyl group of one AA and the amino group of the second AA. backbone of: (N-C-C)X N-terminus & C-terminus Historical 1940’s-1950’s Frederick Sanger First amino acid sequence determined insulin Protein Conformation & Function Functional Protein: 1 or more polypeptide chains Precisely folded, twisted, coiled Uniquely shaped molecule Determined by the A.A. sequence Conformation function Lock & key determines Levels Of Protein Structure 3-D functional shape. Primary Secondary Tertiary Quaternary Primary Sequence of amino acids. Determined by inherited genetic info Secondary Coils and folds Hydrogen bonding b/t segments of chain a helix β pleated sheets Silk/spider web Tertiary Bonding between the R groups. hydrophobic interactions Van der Waals H-bonds ionic bonding disulfide bridges (covalent bond) Quaternary Not in all proteins If two or more polypeptides. Examples: hemoglobin, collagen Is Protein Structure Important? Denaturing Of A Protein Due to altered environment : pH salt Excess Heat ( fever; cooking egg) Chemicals ( solvents) Protein unravels Loses native conformation May be permanent Loses function Example: Egg white cooking Denaturation Chaperonins Proteins Assist proper folding Hollow cylinders—shelters unfolded polypeptide Hydrophyllic interior Correctly folded protein released Nucleic Acids DNA, RNA’s Polymers of nucleotides Contain phosphorous, nitrogen Nucleotides have three parts: nitrogenous base pentose sugar phosphate Homework/Review Protein Review: Concept Check 5.4 page 86; 1,2,3 Hand-written is fine Use your words—not the textbook’s! ----------------------------------------------------------------- Reminder—starting Chap 50 tomorrow—should have read pp.1080 through 1095 and completed Study Guide questions for this section. Complete remainder for Wednesday. Chap. 51 on Thursday and Friday—will get Ch 51 Study Guide and Word Roots for entire unit tomorrow. DNA Deoxyribonucleic Makes Acid. up genes. Genetic information source for life. Double stranded molecule. Double helix. RNA Ribonucleic Acid. Structure and protein synthesis. Genetic information for a few viruses only. Single-stranded molecule. DNA and RNA More will be said about DNA and RNA in future lessons. Summary For each macromolecule, know the following: Sig. elements and monomers Structures Functions Examples given in class
