BIOL 1107 1st Edition Lecture 5 Outline of Last Lecture I Efficiency II Amino Acids a Monomers b Polymerization III Proteins a Why are proteins important Outline of Current Lecture I Amino Acids a Levels of Structure II Folding and Function III Prions and Protein Folding IV Enzymes a Substrate Attachment V Nucleic Acids Current Lecture I Amino Acids The amino group end of a polypeptide is called the N terminus and the carboxyl group end of a polypeptide is called the C terminus These ends are important for solubility in water Levels of Structure o Secondary Structure formed by the hydrogen bonds between the carbonyl group of one amino acid and the amino group of another This structure forms helix and pleated sheets o Tertiary Structure interactions between R groups or between R groups and peptide backbone when secondary structures interact Side chains allow polypeptide to interact with each other Hydrophilic regions are surrounded with hydrophobic regions by folding o Quaternary Structure Has to have at least two polypeptides at tertiary level Example Hemoglobin has a quaternary structure so it can carry more oxygen 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 II Folding and Function Protein folding is often spontaneous because the hydrogen bonds and van der Waals interactions make the folded molecule more energetically stable than the unfolded molecule A denatured unfolded protein is unable to function normally Proteins called molecular chaperones help proteins fold correctly in cells Shape is important III Prions and Protein Folding Prions are improperly folded forms of normal proteins that are present in healthy individuals The amino acid sequence of a prion does not differ from that of a normal protein but shape is radically different Normal protein molecules can be induced to change their shape to the altered form IV Enzymes Enzymes enhance the rate of chemical reactions Without enzymes lowering activation energy humans would burn out and melt before enough heat would be gained Substrate Attachment o Initiation Enzymes have active sites where substrates can bind to forming an enzyme substrate complex o Transition State Facilitation Interactions between enzyme and substrate lower the activation energy required o Termination Products have lower affinity for the active site and are released enzyme is unchanged after reaction 1 Competitive Inhibition occurs when molecule similar in size and shape to substrate competes with the substrate for access to the active site 2 Allosteric Regulation occurs when molecule causes a change in enzyme shape by binding to enzyme at a location other than the active site Can activate or deactivate an enzyme V Nucleic Acids The 5 end of one nucleotide binds to the 3 end of another nucleotide giving DNA directionality Has nitrogenous bases C U T G A
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