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Chemistry
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Why is one H2 molecule released as an obligate byproduct of nitrogenase turnover?
AIt is a mechanistic consequence of the enzyme's electron/proton delivery cycle, built into the reaction stoichiometry regardless of catalyst efficiencyBIt only occurs when the enzyme is inhibited by excess oxygenCIt is a side reaction that can be eliminated by protein engineering without affecting N2 reductionDIt results from adventitious water contamination in the assay
What fundamentally distinguishes a redox titration from an acid–base titration?
AThe titrant and analyte react via electron transfer, and the endpoint is a redox-driven colour change, not a pH indicator changeBRedox titrations never use a buretteCRedox titrations always require heating the flask to boilingDThere is no real difference — both types measure exactly the same thing
Write the fundamental thermodynamic relationship connecting a protein-ligand binding constant to enthalpy and entropy.1 / 8
The binding free energy relates to the association constant Ka by ΔG = -RT ln Ka = ΔH - TΔS, where ΔH is the binding enthalpy (heat released or absorbed on complex formation) and ΔS is the binding entropy (change in disorder of the ligand, protein, and surrounding solvent). A more negative ΔG (tighter binding, larger Ka) can arise from a more favorable (more negative) ΔH, a more favorable (more positive) ΔS, or some combination — the same overall affinity can be reached through very different enthalpy/entropy balances.
Ligand field theory: spectrochemical series, spin state, and Jahn–Teller distortion L4 crystal field theory establishes that ligands split a metal's five d-orbitals into two energy levels separated by a gap Δo. Ligand field theory pushes th
Chemistry
Chemistry · L5 · Ligand Field Theory: Spectrochemical Series, Spin State, and Jahn–Teller Distortion
AA pure element found on the periodic tableBA mixture of a metal with one or more other elementsCA type of acid used to clean metalDA gas released when metal burns
Chemistry
Chemistry · L2 · Alloys — Mixing Metals for a Purpose
What two computational problems does a molecular docking program solve together, and why is speed a necessary compromise?1 / 8
Docking solves a SEARCH problem (finding the ligand's binding pose — position, orientation, and conformation — within the protein's binding site) and a SCORING problem (estimating the binding affinity of each candidate pose) simultaneously, repeated across a very large virtual library (often millions of compounds). Because a rigorous physics-based free-energy calculation for even one pose can take hours of computation, docking scoring functions must be simplified and fast enough to evaluate thousands of poses per compound across a huge library in a practical timeframe — trading rigor for throughput.
Chemistry
Chemistry · L5 · Computational Docking & Drug Design
Isotope Patterns: Reading M, M+1, and M+2 A mass spectrum's molecular-ion region is rarely a single clean peak. Small satellite peaks one and two mass units above M come from the natural abundance of heavier isotopes, and their heights are
What defining feature of an OTTLE cell lets it reach true bulk redox equilibrium quickly?
AA very thin solution layer (~100–200 μm), so the whole optical path electrolyzes on a convenient timescaleBAn unusually high applied potential that forces the reaction to completionCA rotating disk electrode that stirs the solution mechanicallyDThe use of a reference electrode instead of a working electrode
Why molecules have shapes A molecular formula like H₂O or CH₄ tells you which atoms are present, but not how they are arranged in space. VSEPR theory (Valence Shell Electron Pair Repulsion) predicts the actual 3D shape from something you al
The reactivity series is a list of metals ordered from most reactive to least reactive. It helps predict how strongly a metal will react with things like water, acid, or oxygen.
Acids, Bases, and Indicators Substances can be sorted into acids, bases, or neutral. An acid has a sharp or sour taste — think lemon juice or vinegar. A base (also called an alkali when dissolved in water) feels slippery — think soap or bak