Biological Macromolecules Large molecules that perform many important biological functions  Carbohydrates  Lipids  Proteins  Nucleic Acids Many are polymers  Large molecule that is made of repeating units of identical or similar subunits  Each subunit=monomer

Biological Polymerization Accomplished through covalent bonding Often takes place via dehydration reactions which result in the release of a water molecule/bond formed Process can be reversed by hydrolysis which breaks bonds by the addition of water

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

Carbohydrates Comprises sugars and polymers of sugars Used for variety of functions  Energy-simple sugars  Storage of energy-starches  Structural components-cellulose and chitin

Monosaccharides Simple sugars=monomers Usually have chemical composition of C x H 2x O x Can exist as chains or rings (usually rings in solution) Monosaccharides combine to form disaccharides

Sugar Classification Sugars may be classified by:  Number of carbons in chain  Location of carbonyl group  Position of side groups from asymmetrical carbon

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 )

Disaccharide Formation Disaccharides are formed by the dehydration reaction between two monosaccharides Bond between monosaccharides is called the glycosidic linkage  Linkage may occur between different different carbons

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

Storage Carbohydrates Polysaccharides=many monomers in one polymer  Glucose is most common monomer used Starches=plants use for energy storage  Amylose is unbranched chain of glucose monomers Glycogen=animals use glycogen as medium-term energy storage  Glycogen is highly-branched polymer of glucose monomers  Cells contain enough glycogen for approximately one day’s activity

Structural Carbohydrates Cellulose  Most abundant organic compound on earth  Plants use cellulose as structural component of cell walls  Most animals cannot digest Certain bacteria can degrade cellulose Cows and termites have symbiotic relationship w/ bacteria  Fiber in your diet usually means cellulose Not digested so acts as a mechanical cleansing mechanism as it passes through the intestines  Comprises polymerized units of glucose

Starch vs Cellulose Both use 1-4 glycosidic linkage of glucose Starch uses  configuration of glucose  Results in helical molecule Cellulose uses B configuration of glucose  Forms linear strands that interact to form fiber bundles

Structural Carbohydrates 2 Chitin  Comprises polymer of N-acetylglucosamine (NAG) Similar to glucose but possesses a nitrogen-containing side chain Major component of insect and crustacean exoskeleton Major component of fungal cell walls Can be flexible or made rigid by interacting with calcium  Cross-links the structure

Carbohydrate Summary Can be used for energy, storage and structural uses Designated by length of carbon chain, location of carbonyl group, and position of side groups around asymmetric carbons Glucose and modified glucose is used in all three major functions of carbohydrates