BIO 101 1st EdtionLecture 5Outline of Last LectureI. Carbon-Element of LifeII. Carbon SkeletonIII. Isomersa. Structuralb. Geometricc. OpticalIV. HydrocarbonsV. Functional GroupsOutline of Current LectureI. Intro to macromoleculesII. Dehydration SynthesisIII. Proteinsa. Amino acidsb. Polypeptide chainsIV. Levels of Protein Structurea. Primaryb. Secondaryc. Tertiaryd. QuaternaryChapter 5-Macromolecules4 major types of macromolecules: proteins, carbohydrates, nucleic acids and lipidsLarge organic polymers= large molecules made from many identical or similar subunits connected by covalent bondsSubunit= monomer=building blockThis 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 monomersPolymers 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 atomBIO 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 bondsAmino acids= monomerPeptide bonds= name of bondProteins are abundant in living cells- up to 50% dry weightEach protein has a unique 3-D shape= proteins vary extensively in structureDifferent 3-D shapes of protein molecules is responsible for their different functionsExamples 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 proteinsthis 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- ChargedBecause 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 proteinsPolypeptide chains- many amino acids joined together by peptide bondsEach peptide bond is formed by dehydration synthesisBIO 101 1st EdtionWhen amino acids are connected by peptide bonds, a repeating structure is formedRepeating N-C-C-N-C-C-N-C-C-N-C-C is called the backbone of the protein2 ends of the protein are differentone end has a free amine group and is called the N-terminusother end has a free carboxyl-group and is called the C-terminusLevels of protein structurePrimary (1^o) structure= sequence of amino acidsSecondary (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 dueto interactions between ® groups2 major kids of secondary structureTertiary structure (3^o) = describes the 3-D structure due to interactions between ® groups3-D shape is maintained by weak interactions:1. Hydrogen bonds2. 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 togetherBIO 101 1st EdtionQuaternary (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 moleculesIf the protein loses its 3-D shape, it often loses its ability to function*Loss of 3-D shape is called DENATURATIONThe denatured protein still has its primary structure (peptide bonds are not broken), but it is no longer folded up properly into the 3-D shapeWithout the right 3-D shape, most proteins can no longer work properly= loss of 3-Dshape = loss of
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