OAT Physics cheat sheet

Cell theory: all living things are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells by division.

Prokaryotes lack a membrane-bound nucleus and organelles; they have a single circular chromosome, 70S ribosomes, and reproduce by binary fission.

Mitosis produces two genetically identical diploid cells; meiosis produces four genetically distinct haploid gametes through one round of replication and two divisions.

DNA replication is semiconservative: helicase unwinds, primase lays RNA primers, DNA polymerase III extends 5' to 3', and ligase seals Okazaki fragments.

Transcription makes mRNA from the template strand; translation at the ribosome reads codons 5' to 3' using tRNA anticodons and starts at AUG (methionine).

Mendelian ratios: monohybrid cross of heterozygotes gives 3:1 phenotype and 1:2:1 genotype; dihybrid gives 9:3:3:1 when genes assort independently.

Enzyme kinetics: Michaelis-Menten v = (Vmax[S])/(Km+[S]); Km is the substrate concentration at half Vmax, and competitive inhibitors raise apparent Km without changing Vmax.

Photosynthesis light reactions occur in thylakoid membranes producing ATP and NADPH; the Calvin cycle in the stroma fixes CO2 via rubisco.

Mole conversions: n = m/M, particles = n x 6.022e23, and molarity M = mol solute / L solution; dilution obeys M1V1 = M2V2.

Gas laws: PV = nRT with R = 0.0821 L·atm/(mol·K); combined law P1V1/T1 = P2V2/T2; STP molar volume is 22.4 L/mol.

Ideal gas mixtures follow Dalton's law: total pressure equals the sum of partial pressures, and partial pressure = mole fraction x total pressure.

Acid-base: pH = -log[H+], pOH = -log[OH-], pH + pOH = 14 at 25 °C; Ka·Kb = Kw = 1.0e-14 for a conjugate pair.

Henderson-Hasselbalch: pH = pKa + log([A-]/[HA]); a buffer is most effective when pH is within one unit of pKa.

Equilibrium: K > 1 favors products, K < 1 favors reactants; Le Chatelier's principle predicts shifts from concentration, pressure, or temperature changes.

Thermochemistry: ΔG = ΔH - TΔS; a reaction is spontaneous when ΔG < 0, and ΔG° = -RT ln K.

Electrochemistry: E°cell = E°cathode - E°anode; a positive E°cell indicates a spontaneous galvanic reaction, and ΔG° = -nFE°cell.

Hybridization tracks geometry: sp = linear (180°), sp2 = trigonal planar (120°), sp3 = tetrahedral (109.5°); double bonds are sp2, triple bonds sp.

IUPAC naming: identify the longest carbon chain, number to give the lowest locants to substituents, then list substituents alphabetically.

SN2 is one-step, concerted, backside attack, favored by primary substrates and strong nucleophiles; SN1 is stepwise via carbocation, favored by tertiary substrates and polar protic solvents.

E1 and E2 compete with substitution: E2 needs a strong bulky base and anti-periplanar geometry; E1 shares the carbocation intermediate with SN1.

Markovnikov addition of HX to an alkene puts H on the carbon with more hydrogens; anti-Markovnikov occurs with HBr plus peroxides (radical mechanism).

Oxidation states of carbon: primary alcohols oxidize to aldehydes then carboxylic acids; secondary alcohols oxidize to ketones; tertiary alcohols resist oxidation.

Aromaticity requires a planar, cyclic, fully conjugated ring with 4n+2 pi electrons (Hückel's rule); benzene has six pi electrons.

Aldehydes and ketones undergo nucleophilic addition; carboxylic acid derivatives follow the reactivity order acid chloride > anhydride > ester > amide.

Main-idea questions ask for the thesis or overall purpose; the correct answer covers the whole passage, not one supporting detail.

Detail questions are answered by a specific sentence; locate the keyword in the passage and match the answer to the text, not to outside knowledge.

Inference questions require a conclusion that must be true given the passage; reject choices that are plausible but unsupported.

Tone and attitude questions hinge on adjectives and verbs; distinguish objective reporting from advocacy, irony, or skepticism.

EXCEPT and NOT questions are best solved by eliminating the three choices that the passage explicitly supports.

The correct answer to an author's-purpose question often uses a verb plus object, such as 'explain a mechanism' or 'challenge a hypothesis'.

Transition words signal structure: 'however' and 'yet' mark contrast, 'therefore' marks conclusion, and 'for example' marks illustration.

Scope traps include answers that are too broad, too narrow, or reverse the passage's cause-and-effect relationship.

Percent change = (new - old)/old x 100; successive percent changes multiply rather than add, so +20% then -20% gives a net -4%.

Ratios and proportions: set up a/b = c/d and cross-multiply; for part-to-whole problems, total = part / fraction.

Average = sum/count, so sum = average x count; to find a missing value, subtract the known sum from the total sum.

Work-rate problems: combined rate = 1/a + 1/b; time together = ab/(a+b) for two workers.

Distance = rate x time; for round trips at different speeds, average speed = total distance / total time, not the mean of the speeds.

Probability of independent events multiplies; probability of either event uses P(A or B) = P(A) + P(B) - P(A and B).

Combinations count unordered selections nCr = n!/(r!(n-r)!); permutations count ordered arrangements nPr = n!/(n-r)!.

Geometry formulas: circle area = pi r^2, circumference = 2 pi r; triangle area = (1/2)bh; Pythagorean theorem a^2 + b^2 = c^2.

Kinematics: v = v0 + at, x = v0t + (1/2)at^2, and v^2 = v0^2 + 2ax apply when acceleration is constant.

Newton's second law F = ma; on an incline the component along the plane is mg sin(theta) and the normal force is mg cos(theta).

Work-energy: W = Fd cos(theta), kinetic energy = (1/2)mv^2, and gravitational potential energy near Earth = mgh.

Momentum p = mv is conserved in collisions; elastic collisions conserve kinetic energy, inelastic collisions do not.

Circular motion: centripetal acceleration a = v^2/r directed toward the center; gravitational force F = Gm1m2/r^2.

Fluids: pressure at depth P = P0 + rho gh; buoyant force equals the weight of displaced fluid (Archimedes' principle).

Thermodynamics: heat Q = mcΔT; the first law states ΔU = Q - W for work done by the system.

Electricity: Ohm's law V = IR, power P = IV = I^2R, and resistors in series add while parallel resistors add reciprocally.

Waves and optics: v = f lambda; for a converging lens 1/f = 1/do + 1/di, and Snell's law is n1 sin(theta1) = n2 sin(theta2).