Chapter 3 Biological Molecules Aside from water most biologically related molecules contain carbon Organic molecules are molecules containing carbon Carbon atoms are the most versatile building blocks of molecules Carbon has a valence of 4 Can bind to 2 3 or 4 other atoms Another factor which leads to the versatility of organic molecules is the attachment of functional groups see table 3 1 Functional groups are small characteristic groups of atoms which are frequently bonded to the carbon skeleton of organic molecules Functional Groups Similar to the carbon skeleton of an organic molecule Similar to the functional groups attached to the carbon skeleton of an organic molecule Table 3 1 Functional groups Have specific chemical and physical properties Are regions of organic molecules which are frequently chemically reactive Behave consistently from one organic molecule to another Can determine the chemical properties of the organic molecule in which they are located SYNTHESIZING ORGANIC MOLECULES A MODULAR APPROACH Biological molecules are often put together in subunits or modules called monomers the simple molecules combined to form more complex ones monomers into polymers Polymers are chains of similar building blocks or monomers A Monomer is a subunit or building block of a polymer The reaction that forms a polymer from monomers is dehydration synthesis Fig 3 1 Dehydration synthesis is a reaction in which the covalent linkage of the monomers is accompanied by the removal of a water molecule Hydrolysis is the breaking of the covalent bond between two monomers by the addition of water Fig 3 2 Polymer type Monomer type Example CARBOHYDRATES SUGARS LIPIDS FATTY ACIDS Monosaccharides Disaccharides Polysaccharides Glucose Sucrose Starch Glycogen Cellulose Triglycerides Oils fat Wax Plant cuticle Phospholipids Cell Membranes Steroids PROTEINS AMINO ACIDS NUCLEIC ACIDS NUCLEOTIDES Cholesterol Keratin silk DNA RNA Carbohydrates are used as fuels and building material Carbohydrates are organic molecules made of sugars and their polymers Carbohydrates are classified by the number of simple sugars Monomers are simple sugars called monosaccharides Monosaccharides are simple sugars in which carbon hydrogen and oxygen occur in the ratio of 1 2 1 for C H and O Major source of nutrients for cells Glucose is the most common Can be produced by photosynthetic organisms from CO2 H2O and light Monosaccharides can be joined to form disaccharides and polysaccharides Disaccharides are molecules which consist of two monosaccharides joined by a glycosidic linkage See fig 3 7 Glycosidic linkage is a covalent bond formed by a dehydration synthesis between two sugar monomers Fig 3 7 DISACCHARIDE MONOMERS COMMON USE Maltose Lactose Sucrose Glucose Glucose Glucose Galactose Glucose Fructose Important in beer brewing Sugar present in milk Table sugar most common disaccharide Polysaccharides Polysaccharides are macromolecules that are polymers of a few hundred or thousand monosaccharides Formed by enzyme mediated condensation reactions Biological functions Energy storage starch and glycogen see fig 3 3 Structural support cellulose and chitin see figs 3 4 and 3 5 Storage polysaccharide Stored sugars can be hydrolyzed as needed Starch see fig 3 8 is a glucose polymer that is used as a storage polysaccharide in plants Glycogen is a glucose polymer that is used as a storage polysaccharide in animals Stored in the muscle and liver of vertebrates Glycogen If there is more glucose in your bloodstream than your body needs the excess glucose is linked together and stored as glycogen in your muscles and liver When energy is needed glycogen is quickly broken down to release glucose into the bloodstream for short term energy needs Once glycogen stores are full excess glucose gets converted to fat for long term energy needs Carb loading A process by which athletes are able to double or triple the amount of glycogen stored in their muscles Used to delay the onset of muscle fatigue 2 phase process Depletion phase about a week before competition Extremely low carb diet and rigorous exercise Loading phase 2 days before competition Super high carb diet and no exercise Achieves a blood glucose level that is higher than necessary so excess glucose gets converted to glycogen Water Weight The first stages of any diet usually involve rapid and dramatic weight loss This is because glycogen is being depleted in the muscles and liver as caloric intake is reduced Every ounce of glycogen in the body can have as much as four ounces of water bound to it Structural polysaccharides Structural polysaccharides include cellulose and chitin Cellulose see fig 3 9 is a linear unbranched polymer of glucose most abundant organic molecule on the planet differs from starch in the type of linkage different linkage gives different three dimensional structure cellulose reinforces plant cell walls Cellulose Fig 3 9 Hydrogen bonds hold the cellulose strands together cellulose cannot be digested by most animals because they lack the enzyme that can hydrolyze the linkage in cellulose Chitin see fig 3 10 is a structural polysaccharide that is a polymer of an amino sugar forms the exoskeleton of arthropods insects crawfish etc found in the cell walls of some fungi Chitin Fig 3 10 Lipids are mostly nonpolar hydrophobic molecules composed mainly of carbon and hydrogen Lipids are a diverse group of organic molecules that are insoluble in water but will dissolve in nonpolar solvents e g ether chloroform benzene Important lipids are grouped into 3 types 1 fats oils and waxes 2 phospholipids 3 steroids Which is NOT a type of lipid Triglyceride Wax Oil Glycogen Oils Fats and Waxes Characteristics composed of carbon hydrogen and oxygen contain 1 or more fatty acids usually no ring structure Fats and oils are macromolecules constructed from fatty acids and glycerol Glycerol is a three carbon molecule with one hydroxyl group per carbon Fig 3 12 Fatty acids FA are hydrocarbon chains with a carboxyl group at one end Fig 3 6 The hydrocarbon chain or tail is hydrophobic and not water soluble The tail has a long carbon skeleton usually with an even number 16 18 of carbon atoms The carboxyl group or head has the properties of a carboxylic acid Fig 3 6 The FA group is linked through the head to the glycerol and each hydroxyl group on the glycerol can form a linkage with a fatty acid Triglyceride is a fat composed of three fatty acids bonded to one glycerol by ester linkages
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