Ch. 5 Macromolecules BIOL 222 Overview: The Molecules of Life Macromolecules large molecules composed of thousands of covalently connected atoms Built from carbon backbone Also contain large numbers of H and O four classes: Carbohydrates Lipids Proteins Nucleic acids Macromolecules Polymer long molecule consiseng of many similar subunits Monomers Building blocks of polymers Three of the four classes of macromolecules are polymers: Carbohydrates Proteins Nucleic acids
The Synthesis and Breakdown of Polymers dehydra9on synthesis (condensa9on reac9on) occurs when two monomers bond together through the loss of a water molecule hydrolysis Process of breaking polymers down to monomers esseneally the reverse of the dehydraeon reaceon Fig. 5 2 HO 1 2 3 H HO H Short polymer Dehydration removes a water molecule, forming a new bond Unlinked monomer H 2 O HO 1 2 3 4 H Longer polymer (a) Dehydration reaction in the synthesis of a polymer HO 1 2 3 4 H Hydrolysis adds a water molecule, breaking a bond H 2 O HO 1 2 3 H HO H (b) Hydrolysis of a polymer The Diversity of Polymers cells hold thousands of different kinds of macromolecules 2 3 H HO Humans can make up to 150,000 different proteins Macromolecular diversity indicaeve of biological diversity variety of possible polymers virtually limitless from a small set of monomers
Carbohydrates: fuel and building material Carbohydrates Polymers of simple sugar monomers Monosaccharides Polysaccharides Carbohydrate macromolecules Built of monosacharides Monosaccharides Simple Sugars Typically (CH 2 O) n Glucose (C 6 H 12 O 6 ) most common monosaccharide Monosaccharides classified by LocaEon of the carbonyl group (C=O, as aldose or ketose) Number of carbons in the carbon skeleton Fig. 5 3 Trioses (C 3 H 6 O 3 ) Pentoses (C 5 H 10 O 5 ) Hexoses (C 6 H 12 O 6 ) Ketoses Aldoses Glyceraldehyde Dihydroxyacetone Ribose Glucose Galactose Ribulose Fructose
OVen drawn as linear skeletons many sugars form rings in aqueous solueons Monosaccharides major fuel for cells Glucose Simple Sugars raw material for building molecules Carbon skeletons for amino acids and fayy acids Fig. 5 4 (a) Linear and ring forms (b) Abbreviated ring structure Polysaccharides Disaccharide two monosaccharides Joined by dehydraeon synthesis glycosidic linkage covalent bond between 1C of one monosaccharide and O on 4C of next monosaccharide
Fig. 5 5 1 4 glycosidic linkage Glucose Glucose (a) Dehydration reaction in the synthesis of maltose Maltose 1 2 glycosidic linkage Glucose Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose Polysaccharides Polysaccharides polymers of sugars storage and structural roles structure and funceon determined by monomers and posieons of glycosidic linkages Starch Storage Polysaccharides storage polysaccharide of plants as granules within chloroplasts and other plaseds consists enerely of glucose monomers may be thousands of monomers long
Fig. Fig.5 6 5 6 Chloroplast Starch Mitochondria Glycogen granules 0.5 µm 1 µm Amylose Glycogen Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide Storage Polysaccharides Glycogen storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells Fig. Fig.5 6 5 6 Chloroplast Starch Mitochondria Glycogen granules 0.5 µm 1 µm Amylose Glycogen Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide
Structural Polysaccharides Cellulose Polysaccharide major component of plant cell walls also polymer of glucose glycosidic linkages differ The difference is based on two ring forms for glucose: alpha (α) and beta (β) 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 Structural Polysaccharides α glucose Polymers are helical Starch, glycogen β glucose Polymers are straight Cellulose, chien In straight structures H atoms on one strand can 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
Fig. 5 8 Cell walls Cellulose microfibrils in a plant cell wall Microfibril 10 µm 0.5 µm Cellulose molecules β Glucose monomer Enzymes that digest starch by hydrolyzing α linkages can t hydrolyze β linkages in cellulose α amylase Cellulose in human food passes through the digeseve tract as insoluble fiber Some microbes use enzymes to digest cellulose cellulase Structural Polysaccharides Many herbivores, from cows to termites, have symbioec relaeonships with these microbes Chi9n Structural Polysaccharides structural polysaccharide exoskeleton of arthropods structural support for the cell walls of many fungi
Fig. 5 10 (a) The structure (b) Chitin forms the (c) Chitin is used to make of the chitin exoskeleton of a strong and flexible monomer. arthropods. surgical thread. Lipids: diverse group of hydrophobic molecules Lipids only macromolecules that do not form polymers unifying feature of lipids is having liyle or no affinity for water hydrophobic consist mostly of hydrocarbons nonpolar covalent bonds The most biologically important lipids are fats, phospholipids, and steroids Fats Lipids constructed from two types of smaller molecules Glycerol fayy acids Glycerol three carbon alcohol with a hydroxyl group ayached to each carbon fagy acid a carboxyl group ayached to a long carbon skeleton
Fig. 5 11 Fatty acid (palmitic acid) Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage (b) Fat molecule (triacylglycerol)(triglyceride) Fats separate from water Fats because water molecules form hydrogen bonds with each other and exclude the fats Triacylglycerol (triglyceride) three fayy acids joined to glycerol by ester linkages combing acid with an alcohol fayy acid and glycerol FaYy acids FaGy Acids vary in length (number of carbons) and in the number and locaeons of double bonds Saturated fagy acids maximum number of hydrogen atoms possible no double bonds Unsaturated fagy acids one or more double bonds
FaGy Acids saturated fats Fats made from saturated fayy acids solid at room temperature Most animal fats are saturated unsaturated fats or oils Fats made from unsaturated fayy acids liquid at room temperature Plant fats and fish fats are usually unsaturated Fig. 5 12 Structural formula of a saturated fat molecule Stearic acid, a saturated fatty acid (a) Saturated fat Structural formula of an unsaturated fat molecule Oleic acid, an unsaturated fatty acid (b) Unsaturated fat cis double bond causes bending Phospholipids Phospholipid two fayy acids and a phosphate group ayached to glycerol fayy acid tails are hydrophobic phosphate group and its ayachments form a hydrophilic head Amphipathic Both hydrophobic and hydrophilic regions
Fig. 5 13 Hydrophobic tails Hydrophilic head (a) Structural formula Choline Phosphate Glycerol Fatty acids (b) Space-filling model Hydrophilic head Hydrophobic tails (c) Phospholipid symbol Applied Phospholipids Phospholipid bilayer Phospholipids added to water self assemble into a bilayer with the hydrophobic tails poineng toward the interior Phospholipids are the major component of all cell membranes Fig. 5 14 Hydrophilic head WATER Hydrophobic tail WATER