BIO 101 1st Edtion Lecture 5 Outline of Last Lecture I Carbon Element of Life II Carbon Skeleton III Isomers a Structural b Geometric c Optical IV Hydrocarbons V Functional Groups Outline of Current Lecture I Intro to macromolecules II Dehydration Synthesis III Proteins a Amino acids b Polypeptide chains IV Levels of Protein Structure a Primary b Secondary c Tertiary d Quaternary Chapter 5 Macromolecules 4 major types of macromolecules proteins carbohydrates nucleic acids and lipids Large organic polymers large molecules made from many identical or similar subunits connected by covalent bonds Subunit monomer building block This is an example of unity in life because new properties arise when monomers are connected in different ways so there are many kinds of molecules that can be made using the same small set of monomers Polymers are formed from monomers by a common chemical process DEHYDRATION SYNTHESIS removal of H20 One monomer loses an hydroxyl group O H other monomer loses an hydrogen atom H OH H H20 net removal After dehydration synthesis the 2 monomers are covalently bonded to one another and a H20 molecule is released Requires energy Requires biological catalysts enzymes Polymers are broken down into monomers by the opposite process called HYDROLYSIS the covalent bonds holding monomers together are broken by the addition of an H20 molecule One monomer adds a H atom BIO 101 1st Edtion Other monomer adds an OH group The two monomers are now separate Hydrolysis releases energy Proteins polymers of amino acids connected by peptide bonds Amino acids monomer Peptide bonds name of bond Proteins are abundant in living cells up to 50 dry weight Each protein has a unique 3 D shape proteins vary extensively in structure Different 3 D shapes of protein molecules is responsible for their different functions Examples of protein functions structural support transport of molecules movement contractile proteins in muscle cells biological catalysts enzymes ex hemoglobin in red blood cells carries O2 and CO2 example of molecule transport Amino Acids monomers of protein there are 20 common amino acids that make up proteins this part of molecule is common to all amino acids This group is variable The unique characteristics of each of the 20 amino acids are determined by the variable group amino acids are classified by the variable group Polar Nonpolar Charged Because of the asymmetric carbon amino acids can exist in 2 different isomeric forms D and L isomers Usually only the L isomer of amino acids are found in proteins Polypeptide chains many amino acids joined together by peptide bonds Each peptide bond is formed by dehydration synthesis BIO 101 1st Edtion When amino acids are connected by peptide bonds a repeating structure is formed Repeating N C C N C C N C C N C C is called the backbone of the protein 2 ends of the protein are different one end has a free amine group and is called the N terminus other end has a free carboxyl group and is called the C terminus Levels of protein structure Primary 1 o structure sequence of amino acids Secondary 2 o structure repeating twisting and folding of the peptide backbone due to hydrogen bonding between atoms in the backbone repeated N C C NOT due to interactions between groups 2 major kids of secondary structure Tertiary structure 3 o describes the 3 D structure due to interactions between groups 3 D shape is maintained by weak interactions 1 Hydrogen bonds 2 Hydrophobic interactions between nonpolar groups found in interior of protein whereas polar groups are on the surface of protein interacting with H2O However some proteins have covalent links that hold the 3 D shape of the protein together BIO 101 1st Edtion Quaternary 4 o structure association of more than one peptide chain not all proteins have 4 o structure some are simply a single polypeptide chain Ex of protein with 4 o structure is collagen 3 helical polypeptide chains intertwined into a triple helix Quaternary structure is held together by the same kind of forces as 3 D shape mostly weak forces Protein function depends on 3 D shape of the molecule also called the CONFORMATION The shape of the protein allows it to recognize and bind to specific molecules If the protein loses its 3 D shape it often loses its ability to function Loss of 3 D shape is called DENATURATION The denatured protein still has its primary structure peptide bonds are not broken but it is no longer folded up properly into the 3 D shape Without the right 3 D shape most proteins can no longer work properly loss of 3 D shape loss of function
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