ACS BIOCHEMISTRY EXAM QUESTION S WITH
COMPLETE SOLUTIONS LATEST 2024
GRADED A+
Mechanism of Denaturants - ANSWER✔✔Highly soluble, H-binding molecules.Stabilize protein backbone in water. Allows denatured state to be stabilized.Temperature Denaturation of Protein - ANSWER✔✔Midpoint of reaction is Tm.Cooperative Protein Folding - ANSWER✔✔Folding transition is sharp. More reversible.Folding Funnel - ANSWER✔✔Shows 3D version of 2D energy states. Lowest energy is stable protein. Rough funnel is less cooperative.Protein-Protein Interfaces - ANSWER✔✔"Core" and "fringe" of the interfaces. Core is more hydrophobic and is on the inside when interfaced. Fringe is more hydrophilic.π-π Ring Stacking - ANSWER✔✔Weird interaction where aromatic rings stack on each other in positive interaction.σ-hole - ANSWER✔✔Methyl group has area of diminished electron density in center; attracts electronegative groups Fe Binding of O2 - ANSWER✔✔Fe2+ binds to O2 reversible. Fe3+ has an additional + charge and binds to O2 irreversibly. Fe3+ rusts in O2 rich environments.Ka for Binding - ANSWER✔✔Ka = [PL] / [P][L] ϴ-value in Binding - ANSWER✔✔ϴ = (bound / total)x100% ϴ = [L] / ([L] + 1/Ka) Kd for binding - ANSWER✔✔Kd = [L] when 50% bound to protein. 1 / 3
Kd = 1/Ka High-Spin Fe - ANSWER✔✔Electrons are "spread out" and result in larger atom.Low-Spin Fe - ANSWER✔✔Electrons are less "spread out" and are compacted by electron rich porphyrin ring.T-State - ANSWER✔✔Heme is in high-spin state. H2O is bound to heme.R-State - ANSWER✔✔Heme is in low-spin state. O2 is bound to heme.O2 Binding Event - ANSWER✔✔O2 binds to T-state and changes the heme to R-state.Causes a 0.4Å movement of the iron.Hemoglobin Binding Curve - ANSWER✔✔4 subunits present in hemoglobin that can be either T or R -state. Cooperative binding leads to a sigmoidal curve.Binding Cooperativity - ANSWER✔✔When one subunit of hemoglobin changes from T to R-state the other sites are more likely to change to R-state as well. Leads to sigmoidal graph.Homotropic Regulation of Binding - ANSWER✔✔Where a regulatory molecule is also the enzyme's substrate.Heterotropic Regulation of Binding - ANSWER✔✔Where an allosteric regulator is present that is not the enzyme's substrate.Hill Plot - ANSWER✔✔Turns sigmoid into straight lines. Slope = n (# of binding sites).Allows measurement of binding sites that are cooperative.pH and Binding Affinity (Bohr Affect) - ANSWER✔✔As [H+] increases, Histidine group in hemoglobin becomes more protonated and protein shifts to T-state. O2 binding affinity decreases.CO2 binding in Hemoglobin - ANSWER✔✔Forms carbonic acid that shifts hemoglobin to T-state. O2 binding affinity decreases. Used in the peripheral tissues. 2 / 3
BPG (2,3-bisphosphoglycerate) - ANSWER✔✔Greatly reduces hemoglobin's affinity for O2 by binding allosterically. Stabilizes T-state. Transfer of O2 can improve because increased delivery in tissues can outweigh decreased binding in the lungs.Michaelis-Menton Equation - ANSWER✔✔V0 = (Vmax[S]) / (Km + [S]) Km in Michaelis-Menton - ANSWER✔✔Km = [S] when V0 = 0.5(Vmax) Michaelis-Menton Graph - ANSWER✔✔ Lineweaver-Burke Graph - ANSWER✔✔Slope = Km/Vmax Y-intercept = 1/Vmax X-intercept = - 1/Km Lineweaver-Burke Equation - ANSWER✔✔Found by taking the reciprocal of the Michaelis-Menton Equation.Kcat - ANSWER✔✔Rate-limiting step in any enzyme-catalyzed reaction at saturation.Known as the "turn-over number". Kcat = Vmax/Et Chymotripsin - ANSWER✔✔Cleaves proteins on C-terminal endof Phe, Trp, and Tyr Competitive Inhibition Graph - ANSWER✔✔Slope changes by factor of α. Slope becomes αKm/Vmax.X-intercept becomes 1/αKm Y-intercept does not change.Vmax does not change.Uncompetitive Inhibition Graph - ANSWER✔✔Does not change slope.Changes Km and Vmax.Results in vertical shift up and down.Y-intercept becomes α'/Vmax
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