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UB BIO 201 - Work Horses of the Cell and Their Structure

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Bio 201 1st Edition Lecture 4Outline of Last Lecture I. Life vs. Non-lifeII. Polymerization of The Biological MacromoleculesIII. Amino AcidsOutline of Current Lecture I. Protein Structure/ LevelsA. RibonucleaseB. PolypeptidesC. Primary (1°)D. Secondary (2°)E. Tertiary (3°)F. Qauternary (4°)II. Fibrous ProteinsIII. Globular ProteinsA. DomainCurrent LectureI. Protein Structure/ Levels of Structure-Proteins are the workhorses of the cellA. Ribonuclease (RNase) is a protein in the bovine pancreas that secrets massive amounts of digestive enzymes into the small instestine. RNase is the model of a general proteinB. Polypeptides-Proteins are made through the polymerization of amino acids. These amino acid polymers are called polypeptides-2 peptides= dipeptides-Peptides are bound together by a peptide bond joining the Carboxyl (C group) with the Amine (N group)-New additions of amino acids go from the Amine to the CarboxylC. Primary (1°)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-The primary structure of proteins is a linear structure. -This structure is the chemical structure drawn out, the amino sequenceD. Secondary (2°)-The secondary structure of proteins contains alpha-helices and Beta-sheets-Scientist believed that Hydrogen and Ionic bonds played some role in the function of proteins. To test this, scientists boiled ribonuclease and found the protein to stop functioning This meant that hydrogen and ionic bonds do in fact play a role in the function of proteins. Boiling hydrogen and ionic bonds causes the bonds to break, therefore the loss of function was due to these bonds breaking-Regardless of the type of amino acid, when boiled, the protein function will be lost. Hydrogen and/or ionic bonds must be on the polypeptide backbone.-Linus Pauling and Robert Corey were the first men to use x-ray crystallization tostudy Biological Macromolecules. When using this method they discovered that the 2° shape of proteins look similar to DNA, in that they are helical/spiral-Secondary structure contains a-helices and B-sheets that form on proteins due to hydrogen bonding between functional groups on the polypeptide backbone (backbone of the polypeptide that doesn’t include R-group) -a-helices contain intramolecular H-bonds (within same area)-The structure of the a-helix contains a carbonyl oxygen group bonded to an amide group. For every number amino acid carbonyl oxygen group youadd 3 and that is the number of the amino acid amide group (for example1 bonds to 4, 4 bonds to 7) These bonds are extremely stable-a-helices can be shown as a ribbon, a stick and ball, or a barrel-B-sheets (aka B-pleated sheets) contain intermolecular H-bonds between different polypeptides, and intramolecular H-bonds between different parts of same polypeptide (either way B-sheets are bonded separately)-B-sheets are always represented with arrows. These arrows show the direction of the amino acid AmideCarbon. Two amino acid sequences going from A-C are called parallel B-sheets, however if one goes AC and the other goes CA this sequence is antiparallel. E. Tertiary (3°)-Tertiary protein structure is the complete 3D structure of a single polypeptide (including2° structure and R-group)-Contains Covalent (disulfide), Ionic, Hydrogen, and Van der Waal bonds (in order from strongest to weakest)-Non-Polar Van der Waal bonds, are the most abundant bonds in tertiary structure, these bonds get tucked into the interior of the protein-Proteins combined of a single polypeptide this 3° structure is their final conformation or shape.-Not all regions of proteins contain just a-helices or B-sheets, they also can contain random coils F. Qauternary (4°)-The Quaternary protein structure is the structure of multi sub-unit proteins (usually through B-sheet or R-group interactions)-Homomultimers- composed of multiple, identical polypeptide sub-units-Heteromultimers- 2+ different types of polypeptide sub-units (for example, hemoglobinis a heteromultimer polypeptide, containing 2 a-helices and 2 B-sheets)II. Fibrous Proteins-Fibers almost entirely made up of a-helices or B-sheets-These fibers are homogenous structures but contain no particular function, they are also large, and have a low solubility in water-ie. Silk and Keratin (fibers that make up our hair)III. Globular Proteins-These are round, and short, and they are not fibrous therefore they are soluble in waterand they are not homogeneous-These proteins can have multiple domainsA. Domains- the region of the protein that has a known


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UB BIO 201 - Work Horses of the Cell and Their Structure

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