Chapter 5 Notes The Structure and Function of Large Biological Molecules Polymers are large molecules consisting of many identical or similar subunits connected together Monomer is a subunit or building block of a polymer Polymerization the bonding of many small subunits monomers to form long molecules polymers o One of the subunits is a monomer o Two of the subunits make up a dimer o 3 of the subunits make up a polymer Condensation reactions are polymerization reactions in which the covalent linkage of the monomers is accompanied by the removal of a water molecule o Functional groups are removed and water is formed o Large complex molecules are made by condensation reactions Hydrolysis the breaking of the covalent bond between two monomers by the addition of water o Adding water breaks down large molecules Hydrolysis adds a water molecule breaking a polymer bond o The opposite of condensation reactions The four classes of polymers the most important classification of molecules Biological Macromolecules in living systems o Carbohydrates o Lipids o Nucleic acids o Proteins Carbohydrates Carbohydrates are used as fuels and building material Carbohydrates are organic molecules made of sugars and their polymers o Monosaccharides one simple sugar o Disaccharides two simple sugars together o Polysaccharides 3 simple sugars together Without carbohydrates one will die Carbohydrates are not linked to weight gain calories are It doesn t matter what you eat it matters how much you eat Carbohydrates are classified by the number of simple sugars Monomers are simple sugars called monosaccharides In order for a sugar to be classified as a monosaccharide there must be a ratio of 1 carbon to 2 hydrogen to 1 oxygen Carbohydrates contain only carbon hydrogen and oxygen which occur in the ration of 1 2 1 for C H and O Monosaccharides can be joined to form disaccharides and polysaccharides Glycosidic linkage is a covalent bond formed by a dehydration synthesis between two sugar monomers Polysaccharides Polysaccharides are macromolecules that are polymers of a few hundred or thousand monosaccharides Formed by enzyme mediated condensation reactions Biological functions o Energy storage starch and glycogen o Structural support cellulose and chitin Cellulose is in plants as cell walls Chitin is in anything with an exoskeleton or shell a lot of fungi Storage Polysaccharide and mushrooms use chitin too Stored sugars can be hydrolyzed as needed Starch is a glucose polymer that is used as a storage polysaccharide in animals Glycogen is a glucose polymer that is used as a storage polysaccharide in o Stored in the muscle and liver of vertebrates o Glycogen is like fuel Michael Phelps carb loads for competitions in order to increase glycogen levels and sustain his speed in races animals 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 glucose stores are full excess glucose gets converted to fat for long term energy needs The brain can only survive off of glucose it can t burn fat or protein You can t retain information as easily when hungry because your brain is running low on glucose 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 o Depletion Phase about a week before competition Extremely low carb diet and rigorous exercise o 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 stage of any diet usually involves rapid and dramatic weight loss This is because glycogen is being deleted in the muscles and liver as caloric Every ounce of glycogen in the body can have as much as four ounces of intake is reduced water bound to it Structural Polysaccharides Cellulose is a linear unbranched polymer of glucose Structural polysaccharides include cellulose and chitin o Cellulose fiber cannot be digested by the human body It never gets stored in fat because it cannot be digested it doesn t count towards calories o Cellulose cannot be digested by most animals because they lack the enzyme that can hydrolyze the linkage in cellulose o Most abundant organic molecule on the planet o Cellulose reinforces plant cell walls o Hydrogen bonds hold the cellulose strands together o The longer a digestive system in an animal is the more plants cellulose they ingest Animals that can digest cellulose have an enzyme in their stomach that humans lack Chitin is a structural polysaccharide that is a polymer of an amino sugar o Forms the exoskeleton of arthropods insects crawfish etc o Found in the cell walls of some fungi Lipids Lipids are mostly hydrophobic nonpolar molecules with diverse functions 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 lipid types are fats phospholipids and steroids Functions of Fats and Oils Energy storage o One gram of fat stores twice as much energy in its chemical bonds as one gram of polysaccharide o Because of the higher energy per gram energy storage is more compact with fats and oils than with carbohydrates Fats and oils are denser than carbohydrates Why do we crave fats o Fats store enormous amounts of energy o Because of this humans have actually evolved an extremely strong taste preference for foods that are high in fats During times when food was scarce those who had a preference for foods that were high in fat survived This is how the gene became common in future populations the individuals who did not eat the fatty foods died out when food became scarce Olestra fake fat designed to be similar to fats in taste and texture Fats o Cannot be digested by humans o Instead of being a triglyceride with 3 fatty acids linked to a glycerol it has 8 fatty acids attached to a molecule of sucrose o Olestra is so complex that the human body cannot break it down As a result it does not clog the bloodstream Most things that are fat free contain olestra and fool the brain into thinking it ate food with fat in it o It still stimulates the taste buds on your tongue that tell your brain that you are
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