Structure Function of Large Bio Molecules 09 18 2013 Polymers Large molecules consisting of many identical or similar subunits Monomer is a subunit building block of a polymer Polymerization bonding of many subunits monomers to form long connected together molecules polymers Monomer Dimer 2 monomers Polymer Condensation reactions polymerization reactions in which the covalent linkage of the monomers is accompanied by the removal Hydrolysis breaking of the covalent bond between two monomers of a water molecule by the addition of water Four important classes of polymers Carbohydrates o Used as fuels and building material o Organic molecules made of sugars and their polymers o Monosaccharides Disaccharides Polysaccharides o Classified by the number of simple sugars o Monomers are simple sugars called monosaccharides o Contain only carbon hydrogen and oxygen which occur in the ratio of 1 2 1 for C H and O o Glycosidic linkage is a covalent bond formed by a dehydration synthesis between two sugar monomers o 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 structural support cellulose and chitin Stored sugars can be hydrolyzed as needed Glycogen glucose polymer that is used as a storage polysaccharide in animals stored in the muscle and liver of vertebrates Starch is a glucose polymer that is used as a storage polysaccharide in plants o Glycogen 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 o Carb loading 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 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 o Water Weight the first stages of any diet usually involve rapid and dramatic weight loss 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 bounded to it o Structural Polysaccharides cellulose and chitin Cellulose linear un branched polymer of glucose Most abundant organic molecules on the planet Cellulose reinforces plant cell walls Hydrogen bonds hold the cellulose strands together Cannot be digested by most animals because they lack the enzyme that can hydrolyze the linkage in Chitin structural polysaccharide that is a polymer of an cellulose amino sugar Forms the exoskeleton of arthropods insects crawfish etc Found in the cell walls of some fungi Lipids o Mostly hydrophobic molecules with diverse functions o Diverse group of organic molecules that are insoluble in water but will dissolve in non polar solvents e g ether chloroform benzene o Important lipid types are fats phospholipids and steroids o Functions of fats and oils Energy storage one gram of fat stores twice as much energy in its chemical bonds as one gram of Because of the higher energy per gram energy storage is more compact with fats and oils than with polysaccharides carbohydrates Because fats store enormous amounts of energy humans have actually evolved an extremely strong taste preference for foods that are high in fats Olestra fake fat designed to be similar to fats in taste and texture but it cannot be digested by humans Instead of being a triglyceride with 3 fatty acids linked to a glycerol it has 8 fatty acids attached to a molecule of sucrose Still binds to same taste buds but it doesn t get digested because the molecule is so complex Fats humans store fat in adipose tissue cells which swell and shrink as fat is added to or taken from them Insulates the body and protects vital organs Saturated and Unsaturated Saturated all carbons in chain are fully saturated with hydrogen mostly solid butter Makes cookies softer Unsaturated double bonds result in fewer hydrogen atoms on carbon chain an oil healthier less likely to leave residue on the walls and less likely to cause heart disease Phospholipids have 2 ends that behave completely different in water Hydrophilic heads and hydrophobic tails When phospholipids are added to water they self assemble into a bi layer that shield their hydrophobic portion from water Regulate the passage of water in and out of the Steroids class of lipids that includes many hormones Characterized by a carbon skeleton consisting of 4 fused rings with various functional groups cell attached Includes cholesterol a component of animal cell membranes Used as a molecular precursor for many steroids Proteins poly amino acids held together by peptide bonds o Referred to as molecular tools o Called peptides or polypeptides o Two standard functional groups amino and carboxyl Variable side chain R which has other functional groups o The monomers are amino acids o Amino acids are divided into 3 classes determined by the properties of their side chains 20 amino acids Nonpolar 9 Fig 5 17 Polar 6 Fig 5 17 Serine Threonine Cysteine Tyrosine Asparagine Glutamine Charged or Ionic 5 Fig 5 17 Acidic Aspartic acid Glutamic acid Basic Lysine Arginine Histidine o Primary Structure the specific sequence of amino acids in a particular protein Changes in primary structure can result in changes in all the remaining levels of structure o Secondary Structure most proteins have repeated polypeptide segments that are coiled or folded into patterns These are the result of hydrogen bonding between the components of the amino acid backbone not the side chains o Tertiary Structure the overall 3 D shape of a polypeptide that results from interactions between the side chains of the various amino acids Can also involve hydrophobic interactions at the core of the polypeptide Hydrophobic effect is responsible for protein folding Hydrophobic residues core tend to cluster together on the inside of a folded protein away from water o Quaternary Structure not all have this some proteins consist of two or more polypeptide subunits The aggregation
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