ACS Biochemistry Final Exam Study Questions and Answers UPDATED 2024

pKa (chapter 3) - measure of the tendency of a group to give up a proton (acidity); tendency decreases tenfold as pKa increases by one unit thioester bond (1) - compounds with functional group C-S-CoA-C (eg, in acetyl-CoA) zwitterion (3) - dipolar ion with both positive and negative groups but overall neutral charge; can act as either an acid or base Isoelectric point (pI) (chapter 3) - the characteristic pH at which the net electric charge is zero SDS - Sodium Dodecyl Sulfate (chap 3) - detergent used to unfold proteins and give them uniform negative charge SDS Page (3) - chromatography used to separate proteins based on mass. light proteins travel fast than heavier ones PCR - Polymerase chain reaction (3) - copies DNA multiple times to increase sample size Isoelectric focusing (chapt 3) - procedure used to determine the isoelectric pt (pI) of a protein. Protein migrates through gel until pH = pI (net charge = 0) Two-Dimensional Electrophoresis (3) - combines isoelectric focusing and SDS electrophoresis; separates proteins by both molecular weight and pI specific activity (3) - number of enzyme units per mg of total protein (a measure of enzyme purity) activity (3) - total units of a certain enzyme in a solution Peptide bonds (chapter 4) - C-N bond with double bond character due to resonance (C-N bond cannot rotate, and is planar) Edman degredation (3) - used in the sequencing of polypeptides; labels and removes ONLY the amino-residue from a polypeptide. carried out in a machine called a sequenator φ in peptide bonding (chapter 4) - angle around the α-carbon - amide nitrogen bond ψ in peptide bonding (chapter 4) - angle around the α-carbon - carbonyl carbon bond Ramachandran Plot (4) - shows favoreable φ-ψ angle combinations. 3 main "wells" for α-helices, β-sheets, and left handed α-helices Levinthal's Paradox (4) - protein folding cannot be a completely random, trial and error process chaperonins (4) - elaborite protein complexes required for the folding of a number of cellular proteins that do not fold spontaneously Henderson-Hasselbach Equation (2) - pH = pKa + log([A-]/[HA]) which amino acids are not found in α-helices? (4) - glycine and proline. glycine is too flexible, proline is too rigid to rotate. which amino acids are commonly found in β turns? (4) - glycine, because it is small and flexible, and proline because it forms cis conformation in tight turns. β-mercaptoethanol (4) - breaks disulfide bonds