Section 3 · Practice
200 questions · 40 units
Biology
- BiologyA gate in a metabolic pathwayA purified enzyme converts S to P. Initial rates follow v = Vmax[S]/(Km + [S]); enzyme amount is identical throughout. Rates…5 questions
- BiologySelection before matingIn a hypothetical diploid population, juveniles number AA = 360, Aa = 480 and aa = 160. Survival to reproduction is 1 for AA, 1/2 for Aa…5 questions
- BiologyTwo routes into a cellAn artificial cell takes up solute Z through a saturable transporter and a passive leak. The initial uptake is J = Jmax C/(K + C) + kC,…5 questions
- BiologyFollowing a labelled cargoCultured secretory cells receive a short pulse of labelled amino acid followed by unlabelled amino acid. For one cargo protein, the…5 questions
- BiologyA pigment pathway with two switchesIn a model fungus, colourless precursor is converted to yellow pigment by enzyme E1, then yellow to violet by enzyme E2. Functional…5 questions
- BiologyCompetition in a continuously fed vesselTwo microbial species grow on the same limiting nutrient. Their specific growth rates per hour are μP = 0.8S/(1+S) and μQ =…5 questions
- BiologyOxygen flux from a mixed sampleA chamber contains 2 g of photosynthetic tissue. In darkness oxygen concentration falls by 3 micromol/L/min. At a fixed light level it…5 questions
- BiologyWater balance in a flexible vesicleA flexible membrane encloses a fixed amount of impermeant solute N in 1.0 mL water. Initially [N]inside = 200 mmol/L. The vesicle is…5 questions
- BiologyA three-marker test crossA heterozygous insect is test-crossed with a triple-recessive insect. Offspring report the heterozygote's gametes: ABC 348, abc 352, Abc…5 questions
- BiologyReading a signalling circuitIn engineered cells, ligand L activates receptor R, which activates kinase K, which activates transcription factor T. Active T increases…5 questions
- BiologyA two-stage populationA seasonal organism has juveniles J and adults A. The next year's counts are Jnext = 4A and Anext = 0.25J + 0.5A. Reproduction occurs…5 questions
- BiologyLocating carbon in a networkIn a simplified microbial pathway, three-carbon substrate P splits into a two-carbon fragment Q and one-carbon CO2. P carbon 1 becomes…5 questions
- BiologyCells that outlast an antibioticA culture of a bacterium in exponential growth, 1.0 × 10⁸ colony-forming units (CFU) per mL, was exposed to a high concentration of…5 questions
- BiologyKeeping warm through the legsIn the legs of a wading bird, arteries carrying blood towards the feet run in close contact with veins returning blood to the body. In a…5 questions
- BiologyLeaves grown in a richer atmospherePlants of one species were grown from seed in chambers with CO₂ at either 400 or 800 parts per million (ppm); light, water and…5 questions
- BiologyAmplifying a hormone signalA hormone binds a receptor on a liver cell. In one model of the signalling pathway, each hormone-receptor complex activates 20 G-protein…5 questions
Chemistry
- ChemistryChemistry unit 1A synthetic weak acid HA is being recovered from water. Only neutral HA enters an organic solvent. Its distribution ratio is…5 questions
- ChemistryChemistry unit 2A dissolved reagent X reacts with Y to form P. Initial rates in arbitrary units are measured before appreciable depletion and rounded to…5 questions
- ChemistryChemistry unit 3Two half-cells contain the same metal M and its divalent ion M2+. At the stated temperature, the reduction potential is E = E0 + 0.030…5 questions
- ChemistryChemistry unit 4A starting compound A converts to intermediate B, which converts irreversibly to C. Each step is first order and no other reactions…5 questions
- ChemistryChemistry unit 5Two stable solutes X and Y absorb light independently. For a 1 cm cell their absorbances are A(400)=2x+y and A(500)=x+3y, where x and y…5 questions
- ChemistryChemistry unit 6A reversible isomerisation U to V has ΔH = +12 kJ mol-1 and ΔS = +40 J mol-1 K-1, treated as constant between 250 and 400 K. Standard…5 questions
- ChemistryChemistry unit 7A mixture contains free ions M2+ and N2+, initially each at 0.010 mol L-1. Addition of a soluble source of X- can precipitate MX2 or…5 questions
- ChemistryChemistry unit 8An ester R-C(=O)-O-R′ is hydrolysed to a carboxylic acid and an alcohol R′OH. Researchers compare two possible pathways. In pathway I,…5 questions
- ChemistryChemistry unit 9Gas A reacts on a solid surface. A second gas B does not react but competes for the same sites. A proposed initial-rate model is v =…5 questions
- ChemistryChemistry unit 10A simplified condensation joins bifunctional monomers into linear chains. Each new linkage releases one water molecule. No rings or…5 questions
- ChemistryChemistry unit 11A sealed vessel initially contains only gaseous D2, which dissociates as D2 ⇌ 2D. At a fixed temperature all gases are ideal. If α is…5 questions
- ChemistryChemistry unit 12A chiral substrate S exists as R and S configurations; call them R-form and S-form to avoid confusing the substrate name. Route I…5 questions
- ChemistryShelf life of an ester drugA drug containing an ester group is hydrolysed in aqueous solution by a first-order process. At 25°C its half-life is 40 days. Over the…5 questions
- ChemistryA buffer for cell cultureA hypothetical buffer B is used in a cell-culture model. At 37°C its acid form, HA, and base form, A⁻, are related by pH = 7.50 +…5 questions
- ChemistryTwo routes for substitutionAlkyl bromides react with nucleophiles by two mechanisms. In the SN2 mechanism, the nucleophile attacks the carbon bearing bromine from…5 questions
- ChemistryIron in a tablet by absorbanceIron(II) forms an orange complex with phenanthroline that absorbs strongly at 510 nm, with molar absorptivity 1.1 × 10⁴ L mol⁻¹ cm⁻¹.…5 questions
Physics
- PhysicsPhysics unit 1An engineer studies spherical beads settling in a deep, still liquid. The bead density is ρb, liquid density ρl, bead radius r,…5 questions
- PhysicsPhysics unit 2A small experimental chamber is described by C dT/dt = P − K(T−Ta), where T is its uniform temperature, Ta = 20 °C is ambient…5 questions
- PhysicsPhysics unit 3An optical bench uses a thin converging lens of focal length f = 12 cm. For a real object and a real image, object distance u and image…5 questions
- PhysicsPhysics unit 4A sensor circuit has an ideal 12 V supply, a fixed resistor R and a temperature-sensitive resistor X in series. The measured output V is…5 questions
- PhysicsPhysics unit 5A cart of mass m moves horizontally with a fan providing constant forward force F. Rolling resistance is negligible. Air drag has…5 questions
- PhysicsPhysics unit 6A narrow tube contains air and has one open end and one end closed by a movable piston. At fixed sound frequency f, resonance occurs at…5 questions
- PhysicsRiding a zip lineA 60 kg rider starts from rest at the top of a zip line and descends a vertical height of 20 m along 200 m of cable. The rider arrives…5 questions
- PhysicsAn electric kettleAn electric kettle is rated at 2300 W when connected to a 230 V supply. Its heating element behaves as a fixed resistance. The kettle is…5 questions