Optometry Admission Test (OAT): Free Preparation Guide Study Guide

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A neutral solute enters cells only when a specific carrier is present. Uptake follows the concentration gradient and levels off as extracellular concentration rises. Identify carrier-mediated facilitated diffusion because protein dependence and saturation do not establish active transport.

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Two solutions contain the same total solute concentration, but one contains a solute that readily enters the cell. Predict cell volume using the nonpenetrating solute concentrations, rather than assuming equal total concentrations guarantee equivalent tonic effects.

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A researcher blocks electron transfer between photosystem II and downstream carriers. Predict reduced linear electron flow, impaired NADPH production and reduced proton-gradient formation through that pathway. Do not infer that carbon dioxide directly supplies the released oxygen.

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A cell with two homologous pairs completes meiosis I normally. Each daughter has one chromosome from each pair, with sister chromatids still attached. Explain why the daughters are haploid despite retaining duplicated chromosomes before meiosis II.

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Four products from one meiotic division include two gametes with the normal chromosome number, one with an extra chromosome and one missing that chromosome. Assuming a single nondisjunction event, place the error in meiosis II.

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Two heterozygous plants are crossed. The problem states that the heterozygote has an intermediate flower color. Predict three phenotype classes in a 1:2:1 ratio because each genotype has a distinguishable phenotype under incomplete dominance.

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An AaBb parent is testcrossed with aabb. Offspring predominantly show the two parental allele combinations rather than four equally frequent classes. Interpret the pattern as evidence consistent with linked loci, rather than forcing a 1:1:1:1 prediction.

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An unknown particle contains genetic material and capsid proteins but produces new particles only inside living host cells. Classify it as viral on those structural and replication clues; small size alone would not distinguish it from a bacterium.

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Body temperature rises during exercise, and sweating increases heat loss. Explain that the response opposes the original rise. If temperature later falls toward its regulated range, the stimulus driving the cooling response diminishes rather than continuing unchecked.

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A population meeting the model assumptions has a recessive phenotype frequency of 0.09. Calculate q = 0.30, p = 0.70 and a heterozygote frequency of 0.42. Explain why changing survival across genotypes would undermine the equilibrium assumption.

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For 2H2 + O2 → 2H2O, a mixture contains 3 mol H2 and 2 mol O2. Hydrogen can form 3 mol water, while oxygen could form 4 mol. Therefore hydrogen limits production, leaving oxygen in excess.

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A sealed rigid vessel warms from 27°C to 127°C. Convert to approximately 300 K and 400 K. Its pressure increases by a factor of 400/300, or about 1.33, because neither gas amount nor vessel volume changes.

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Compare similarly sized molecules, one containing an alcohol group and one containing only hydrocarbon bonds. Predict stronger intermolecular association for the alcohol through hydrogen bonding, while assessing water solubility separately because a large hydrocarbon portion can reduce compatibility.

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A 0.10 M weak acid has Ka = 1.0 × 10⁻⁵. Estimate [H+] = 1.0 × 10⁻³ M and pH = 3.00. Dissociation is about 1% of the initial concentration, supporting the approximation.

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A solution initially contains equal amounts of HA and A−. A small strong-acid addition converts some A− into HA, lowering their ratio and the pH slightly. A large addition exhausting A− defeats the same buffering mechanism.

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Doubling A at fixed B increases rate fourfold; doubling B at fixed A doubles rate. Infer rate = k[A]²[B]. If both concentrations double simultaneously, predict an eightfold increase rather than adding the two separate changes.

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A process has ΔH = +30 kJ/mol and ΔS = +100 J/(mol·K). Convert entropy to 0.100 kJ/(mol·K). The crossover is 300 K; above that temperature, the stated approximation gives negative ΔG.

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A metal electrode loses mass while its atoms enter solution as cations. Assign it as the anode if that dissolution is the oxidation half-reaction. Electrons released there travel through the wire toward the electrode where reduction occurs.

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A mechanism shows a full-headed arrow from an oxygen lone pair to a proton and another from the original H–X bond to X. Predict protonated oxygen and the conjugate base X, then verify valence and charge conservation.

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Compare a primary bromide and a tertiary bromide exposed to the same effective nucleophile. Predict the primary substrate is more accessible for SN2 attack. For a chiral reacting carbon, track spatial inversion rather than assuming its R/S label must always switch.

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An acid with pKa 5 reacts with a base whose conjugate acid has pKa 10. Estimate an equilibrium constant near 10⁵ for proton transfer toward products. Reversing the reaction reverses the exponent and favors the original reactants.

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Route: propan-1-ol → propyl tosylate using TsCl and pyridine under dry, mild conditions; isolate the intermediate, then treat it with NaI in acetone at room temperature to obtain 1-iodopropane. All three carbons remain in the product. In contrast, treating propyl tosylate with a bulky strong base such as potassium tert-butoxide, especially with heating, favors E2 removal of a β-hydrogen and tosylate to form propene. The iodide route therefore selects conditions supporting the required carbon–iodine bond rather than an alkene.

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A sample shows a broad band near 3350 cm⁻¹ and lacks a strong carbonyl-region absorption. Among otherwise compatible candidates, favor an alcohol over a ketone. Then use additional structural evidence to distinguish different alcohol isomers.

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A spectrum includes a one-proton signal near 9.8 ppm and other signals consistent with an alkyl chain. Consider an aldehyde-containing candidate. An accompanying carbonyl IR absorption strengthens that assignment, while the remaining NMR pattern constrains the chain structure.

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Two drawings have identical bonds and one tetrahedral center with four different groups. Their arrangements are nonsuperimposable mirror images. Identify enantiomers rather than constitutional isomers, and distinguish that relationship from two rotated drawings of the same configuration.

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An organic solution contains a carboxylic acid and a neutral hydrocarbon. Shake it with an appropriate aqueous base, allow the layers to separate, and retain the aqueous layer containing the carboxylate. Subsequent acidification regenerates the neutral acid for recovery.

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A passage introduces conflicting explanations, describes experiments favoring one, then notes an unresolved limitation. Select a summary stating that the evidence favors that explanation provisionally, rather than one describing only the first experiment or claiming the debate is settled.

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A passage reports faster growth only when both light and a nutrient were increased. Reject a paraphrase attributing the improvement to increased light alone. Preserve the joint condition and avoid assigning separate effects that the described comparison did not isolate.

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A passage says an effect appeared in treated samples but disappeared when a specified component was removed. Infer that the component was necessary under the tested conditions, rather than that it is sufficient by itself or necessary in every possible setting.

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A passage states that a treatment may improve performance in a subgroup during short observations. Choose a conclusion retaining possibility, subgroup and observation length. Reject a universal claim that the treatment improves everyone’s performance indefinitely.

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A passage presents a researcher's explanation, then says its predictions were not observed and offers another account. Identify the original explanation as a cited view the author questions, rather than treating its initial presentation as the author's final position.

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After two paragraphs favoring a proposed mechanism, a third describes a condition where the prediction failed. Identify that paragraph as limiting the mechanism's applicability. Its experimental subject alone does not make it another uncomplicated supporting example.

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A fictional study finds better performance among people who voluntarily use an aid. Users also practise more. Identify practice as a possible alternative explanation, and conclude that the reported association alone cannot isolate the aid's causal contribution.

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A passage tests a coating by exposing coated samples to heat but leaving uncoated samples at room temperature. Explain that coating and temperature changed together. A comparison using equal temperature exposure would better isolate the coating's contribution.

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A fictional passage defines efficiency as correctly completed tasks per minute. A group completes more tasks but makes enough errors to have fewer correct tasks per minute. Under that definition, total activity alone does not demonstrate greater efficiency.

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A passage says a model predicted the average result; however, it failed for one subgroup. Preserve both findings: some predictive success and a limitation. Do not summarize the transition as either complete validation or total rejection of the model.

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Two fictional explanations predict an effect in warm conditions, but only one predicts it in darkness. Evidence that the effect persists in darkness better distinguishes the accounts than another warm-condition observation, assuming the passage specifies those predictions.

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A fictional hypothesis predicts a response only above a threshold. A study below that threshold observes no response. Explain that this result does not contradict the prediction, whereas a reliable absence above the threshold would more directly challenge it.

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One fictional experiment reports a short-term increase, while another finds no difference after a week. Reconcile them as compatible with a temporary effect if their measures and conditions otherwise match. Neither finding alone establishes a lasting improvement.

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A 4 kg cart experiences 18 N rightward and 6 N leftward. The net horizontal force is 12 N rightward, giving acceleration 3 m/s² rightward. Balanced vertical forces do not add to that horizontal acceleration.

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A cart starts at 2 m/s and accelerates at 3 m/s² for 4 seconds along the positive axis. Its displacement is 2×4 + ½×3×16 = 32 m, and its final velocity is 14 m/s.

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A horizontal beam has a 20 N downward load 0.30 m left of its pivot. A downward force 0.20 m right must be 30 N to balance its 6 N·m torque. The pivot reaction must also balance total force.

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A 2 kg cart moving at 3 m/s sticks to a stationary 1 kg cart on a track with negligible external horizontal impulse. Their combined velocity is 6/3 = 2 m/s. Momentum is conserved, but kinetic energy decreases.

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An object begins with 50 J of mechanical energy and loses 12 J through frictional work during motion. Its final mechanical energy is 38 J. Explain that the missing mechanical energy is transferred to other energy forms.

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A wave has frequency 50 Hz and wavelength 0.40 m, so its speed is 20 m/s. In a second medium with speed 30 m/s and unchanged source frequency, its wavelength becomes 0.60 m.

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An oscillator is at maximum positive displacement. Predict zero instantaneous speed and acceleration directed toward equilibrium. As it passes equilibrium, predict maximum speed but zero restoring acceleration, assuming ideal simple harmonic behavior without additional forces.

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A point lies 0.80 m below the water surface in an open container, so Psurface = Patmospheric. With density 1000 kg/m³ and g = 10 m/s², Pgauge = 1000×10×0.80 = 8000 Pa. Its absolute pressure is local atmospheric pressure plus 8000 Pa.

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A gas receives 120 J of heat and does 45 J of expansion work. Its internal energy increases by 75 J under the stated convention. If instead 45 J of work is done on it, the increase becomes 165 J.

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Connect 6 Ω and 3 Ω resistors in parallel across an ideal 12 V source. Their equivalent resistance is 2 Ω, total current is 6 A, and branch currents are 2 A and 4 A respectively.

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A real object is 10 cm from a converging lens with focal length 15 cm. Calculate 1/di = 1/15 − 1/10, giving di = −30 cm. Magnification is +3, so the image is virtual, upright and enlarged.

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A shop sells 12 tickets, some at $8 and others at $5, collecting $81. Let x be the $8 tickets: 8x + 5(12 − x) = 81. Solving gives x = 7, leaving five lower-priced tickets.

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One pump fills a tank in six hours and another in three hours, with unchanged rates when operating together. Their combined rate is 1/6 + 1/3 = 1/2 tank per hour, so filling takes two hours.

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A price rises from $100 by 20% and then falls by 20%. Calculate 100×1.20×0.80 = $96. The net change is a 4% decrease, because the second change applies to $120 rather than the original $100.

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Solve −3x + 6 ≥ 15. Subtract six to get −3x ≥ 9, then divide by −3 and reverse the relation: x ≤ −3. Substitution of −4 satisfies the original inequality, while zero does not.

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Compare x and x² when 0 < x < 1. Multiplying x < 1 by positive x gives x² < x, so x is greater throughout the allowed interval. Without that interval, examples such as x = 2 change the ordering.

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The target is whether x is positive, and a statement says x > 5. That statement is sufficient despite leaving x's exact value unknown. A statement saying x² = 9 is insufficient because x could be either positive or negative.

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Among 40 members who use a service, 10 also attend a workshop; there are 100 members overall. The probability of workshop attendance given service use is 10/40, or 0.25, rather than 10/100.

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A bag contains four red and six blue counters. The chance of drawing two red counters without replacement is (4/10)(3/9) = 2/15. Replacing the first counter would instead keep the second probability at 4/10.

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Ten observations have mean 60 and thirty have mean 80. Their combined mean is (10×60 + 30×80)/40 = 75. The larger group contributes more observations, so its mean receives proportionally greater weight.

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A cost graph rises from $20 at zero units to $50 at ten units. Its slope is $3 per unit and intercept is $20. Use cost = 20 + 3x within the stated range and check any capacity limits.