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ACS BIOCHEMISTRY EXAM ACTUAL EXAM WITH
QUESTIONS AND 100% CORRECT VERIFIED ANSWERS/ ACS
BIOCHEMISTRY EXAM LATEST 2025-2026 (BRAND NEW!!)
Henderson-Hasselbach Equation pH = pKa + log ([A-] / [HA]) FMOC Chemical Synthesis Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is used as a protecting group on the N-terminus. Salting Out (Purification) Changes soluble protein to solid precipitate. Protein precipitates when the charges on the protein match the charges in the solution. Size-Exclusion Chromatography Separates sample based on size with smaller molecules eluting later. Ion-Exchange Chromatography Separates sample based on charge. CM attracts +, DEAE attracts -. May have repulsion effect on like charges. Salt or acid used to remove stuck proteins. Hydrophobic/Reverse Phase Chromatography
Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute with non-H-bonding solvent (acetonitrile). Affinity Chromatography Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or similar ligand. SDS-PAGE Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of mass with smaller molecules moving faster. Visualized with Coomassie blue. SDS Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge. Isoelectric Focusing Variation of gel electrophoresis where protein charge matters. Involves electrodes and pH gradient. Protein stops at their pI when neutral. FDNB (1-fluoro-2,3-dinitrobenzene) FDNB reacts with the N-terminus of the protein to produce a 2,4-dinitrophenol derivative that labels the first residue. Can repeat hydrolysis to determine sequential amino acids.
Glycine Ramachandran Plot Glycine can adopt more angles. (H's for R-group). Proline Ramachandran Plot Proline adopts fewer angles. Amino group is incorporated into a ring. α-helices Ala is common, Gly & Pro are not very common. Side-chain interactions every 3 or 4 residues. Turns once every 3.6 residues. Distance between backbones is 5.4Å. Helix Dipole Formed from added dipole moments of all hydrogen bonds in an α-helix. N-terminus is δ+ and C- terminus is δ-. ß-sheet Either parallel or anti-parallel. Often twisted to increase strength. Anti-parallel ß-sheet Alternating sheet directions (C & N-termini don't line-up). Has straight H-bonds.
Parallel ß-sheet Same sheet directions (C & N-termini line up). Has angled H-bonds. ß-turns Tight u-turns with specific phi-psi angles. Must have gly at position 3. Proline may also be at ß-turn because it can have a cis-omega angle. Loops Not highly structured. Not necessary highly flexible, but can occasionally move. Very variable in sequence. Circular Dichroism Uses UV light to measure 2° structure. Can be used to measure destabilization. Disulfide-bonds Bonds between two - SH groups that form between 2° and 3° structure. ß-mercaptoethanol Breaks disulfide bonds.
Highly soluble, H-binding molecules. Stabilize protein backbone in water. Allows denatured state to be stabilized. Temperature Denaturation of Protein Midpoint of reaction is Tm. Cooperative Protein Folding Folding transition is sharp. More reversible. Folding Funnel Shows 3D version of 2D energy states. Lowest energy is stable protein. Rough funnel is less cooperative. Protein-Protein Interfaces "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 Weird interaction where aromatic rings stack on each other in positive interaction. σ-hole
Methyl group has area of diminished electron density in center; attracts electronegative groups Fe Binding of O Fe2+ binds to O2 reversible. Fe3+ has an additional + charge and binds to O2 irreversibly. Fe3+ rusts in O2 rich environments. Ka for Binding Ka = [PL] / [P][L] ϴ-value in Binding ϴ = (bound / total)x100% ϴ = [L] / ([L] + 1/Ka) Kd for binding Kd = [L] when 50% bound to protein. Kd = 1/Ka High-Spin Fe Electrons are "spread out" and result in larger atom.
Homotropic Regulation of Binding Where a regulatory molecule is also the enzyme's substrate. Heterotropic Regulation of Binding Where an allosteric regulator is present that is not the enzyme's substrate. Hill Plot Turns sigmoid into straight lines. Slope = n (# of binding sites). Allows measurement of binding sites that are cooperative. pH and Binding Affinity (Bohr Affect) As [H+] increases, Histidine group in hemoglobin becomes more protonated and protein shifts to T- state. O2 binding affinity decreases. CO2 binding in Hemoglobin Forms carbonic acid that shifts hemoglobin to T-state. O2 binding affinity decreases. Used in the peripheral tissues. BPG (2,3-bisphosphoglycerate) Greatly reduces hemoglobin's affinity for O2 by binding allosterically. Stabilizes T-state. Transfer of O can improve because increased delivery in tissues can outweigh decreased binding in the lungs.
Michaelis-Menton Equation V0 = (Vmax[S]) / (Km + [S]) Km in Michaelis-Menton Km = [S] when V0 = 0.5(Vmax) Michaelis-Menton Graph Lineweaver-Burke Graph Slope = Km/Vmax Y-intercept = 1/Vmax X-intercept = - 1/Km Lineweaver-Burke Equation Found by taking the reciprocal of the Michaelis-Menton Equation. Kcat Rate-limiting step in any enzyme-catalyzed reaction at saturation. Known as the "turn-over number". Kcat = Vmax/Et
Non-Competitive Inhibition Graph Form of mixed inhibition where the pivot point is on the x-axis. Only happens when K1 is equal to K1'. Ionophore Hydrophobic molecule that binds to ions and carries them through cell membranes. Disrupts concentration gradients. ΔGtransport Equation ΔGtransport = RTln([S]out / [S]in) + ZFΔΨ Pyranose vs. Furanose Pyranose is a 6-membered ring. Furanose is a 5-membered ring. Mutarotation Conversion from α to ß forms of the sugar at the anomeric carbon. Anomeric Carbon Carbon that is cyclized. Always the same as the aldo or keto carbon in the linear form.
α vs. ß sugars α form has - OR/OH group opposite from the - CH2OH group. ß form has - OR/OH group on the same side as the - CH2OH group. Starch Found in plants. D-glucose polysaccharide. "Amylose chain". Unbranched. Has reducing and non- reducing end. Amylose Chain Has α-1,4-linkages that produce a coiled helix similar to an α-helix. Has a reducing and non-reducing end. Amylopectin Has α-1,4-linkages. Has periodic α-1,6-linkages that cause branching. Branched every 24-30 residues. Has reducing and non-reducing end. Reducing Sugar Free aldehydes can reduce FeIII or CuIII. Aldehyde end is the "reducing" end. Glycogen Found in animals. Branched every 8-12 residues and compact. Used as storage of saccharides in animals.
Type II Integral Membrane Protein Membrane protein with N-terminus inside and C-terminus outside Type III Integral Membrane Protein Membrane protein that contains connected protein helices Type IV Integral Membrane Protein Membrane protein that contains unconnected protein helices Bacteriorhodopsin Type III integral membrane protein with 7 connected helices. ß-Barrel Membrane Protein Can act as a large door. Whole proteins can fit inside. α-hemolysin Secreted as a monomer. Assembles to punch holes in membranes.
Cardiolipin "Lipid staple" that ties two proteins (or complexes) together in a membrane. Formed from two phosphoglycerols. Hydrolysis of Nucleotides Base hydrolyzes RNA, but not DNA. DNA is stable in base because of 2' deoxy position. Chargaff's Rule Ratio of A:T and G:C are always equal or close to 1 DNA Double-Helix Opposite strand direction. 3.4Å distance between complementary bases. 36Å for one complete turn. A-form DNA Condensed form of DNA. Deeper major groove and shallower minor groove. B-form DNA Watson-Crick model DNA. Deep, wide major groove. Z-form DNA
G-C base pairs have 3 H-bonds A-T base pairs have 2 H-bonds GPCR (G-protein coupled receptor) α-helical integral membrane proteins. Is a αßɣ heterotrimer. ß-adrenergic receptor Prototype for all GPCR's. Bind adrenaline/epinephrine to stimulate breakdown of glycogen. Step 1 of Epinephrine Signal Transduction Epinephrine binds to its specific receptor Step 2 of Epinephrine Signal Transduction Hormone complex causes GDP bound to α-subunit to be replaced by GTP, activating α-subunit Step 3 of Epinephrine Signal Transduction Activated α-subunit separates from ßɣ-complex and moves to adenylyl cyclase, activating it. Step 4 of Epinephrine Signal Transduction
Adenylyl cyclase catalyzes the formation of cAMP from ATP Step 5 of Epinephrine Signal Transduction cAMP phosphorylates PKA, activating it Step 6 of Epinephrine Signal Transduction Phosphorylated PKA causes an enzyme cascade causing response to epinephrine Step 7 of Epinephrine Signal Transduction cAMP is degraded, reversing activation of PKA. α-subunit hydrolyzes GTP to GDP and becomes inactivated. cAMP Secondary messenger in GPCR signalling. Formed from ATP by adenylyl cyclase. Activates PKA (protein kinase A). AKAP Anchoring protein that binds to PKA, GPCR, and adenylyl cyclase. GAPs (GTPase activator proteins)
