AAMC Practice Test 3 - C/P Review

Suppose that a blood vessel of cross-sectional area A carries microbubbles at a speed v into a capillary bed. If the capillary bed is made up of n capillaries, each with cross-sectional area a, with what speed will the blood flow in the capillary bed?

According to the continuity equation, if u is the speed of flow in the capillary bed, then A x v = n x a x u, so u = A x v/(n x a). So the answer is B.

Which expression can be used to calculate the solubility of CaCO3? A. Ksp = [Ca2+][CO32-]/[CaCO3] B. Ksp = [Ca2+][CO32-] C. Ksp = [CaCO3]/[Ca2+][CO32-] D. Ksp = [Ca2+]2[CO32-]2

The answer is B because Ksp is equal to the products over the reactants. As the product in this case is a solid it would just be equal to the reactants (the aqueous parts of the equation). Thus, B is the right answer.

What can be inferred from the results of Scheme A about the relative thermodynamic stabilities of Compounds 4a and 4b? A. They are equally stable. B. Compound 4a is less stable than Compound 4b. C. Compound 4a is more stable than Compound 4b. D. Nothing can be inferred about relative thermodynamic stabilities.

The answer is C - Compound 4a is more stable than Compound 4b. This is because there is a higher percentage of compound 4a than compound 4b at equilibrium (60% vs. 40%). For a thermodynamic mixture the relative mole ratio of products is directly related to the relative stability of these products. Thus, 4a is more stable than 4b.

The equilibrium shown in Equation 3 can be shifted to the left by which of the following? A. Adding more resin B. Adding Ca2+ ions C. Adding Na+ ions D. Increasing the concentration of anion on the plastic beads

The answer is C because adding Na+ ions to Reaction 3 will cause the equilibrium to shift to the left, which removes Na+ ions.

Which of the following compounds is most likely to be a major product in Step 2 if the aldol condensation is NOT followed by a dehydration reaction?

The answer to this is A. because an aldol addition occurs if there is no dehydration in an aldol condensation.

Which molecule most likely binds to a steroid hormone receptor?

The answer to this is D because it is the only option choice with four (4) fused rings - characteristic of a steroid.

Given that water is the solvent for this type of experiment, what is the best site for tritium labeling? A. I B. II C. III D. IV

The answer to this question is A. I. This is because the best site for tritium labeling would not exchange the tritium (3H) ions for protons in water. all of the N-H sites (II-IV) would readily exchange tritium protons due to their lone pair but the C-H site (I) lacking a lone pair would retain its tritium label.

Which structure represents a component of the HRP cofactor?

The answer to this question is A. because the cofactor is heme, which is a porphyrin. The basic unit of a porphyrin is the pyrrole ring, a five-sided heterocycle containing one nitrogen atom.

Which statement about the unfolding cooperativity and pK of the oligonucleotides is consistent with the data in Figure 1? A. The oligonucleotide with the highest pK displays the highest unfolding cooperativity. B. The oligonucleotide with the lowest pK displays the highest unfolding cooperativity. C. The oligonucleotide with the second highest pK displays the highest unfolding cooperativity. D. The oligonucleotide with the second highest pK displays the lowest unfolding cooperativity.

The answer to this question is B 5hmC-WT is the most "S-shaped" so it has the highest cooperativity. pK is the -log of K and K is the equilibrium constant which is the [unfolded]/[folded], because that was the reaction being tested. So larger K values are more unstable because for a given pH or temperature they are more unfolded. Since a larger K means a smaller pK then smaller pK values mean that something is more unstable, and given the Tm at the end, 5hmc-WT is the least stable. The trace of CD vs pH show use that 5hmc-WT is also the most cooperative. So the species with the lowest pK (lowest stability, 5hmc-WT) is also the species that is most cooperative.

The complement to the WT sequence does NOT contain which nucleoside? A. Deoxyadenosine B. Deoxycytidine C. Deoxyguanosine D. Deoxythymidine

The answer to this question is B because the WT sequence does not contain deoxyguanosine. The complementary sequence therefore will not include deoxycytidine. (No G's in the string means that the complement will not have any C's).

What is the total amount of charge and energy, respectively, that the capacitor will store if it is connected to the battery on the railcar? A. 0.12 C and 14.4 J B. 1.20 C and 7.20 J C. 1.44 C and 0.12 J D. 7.20 C and 1.20 J

The answer to this question is B. 1.20 C and 7.20 J. This is because the charge is given by the formula q = CV and the relation 100mF x 12 V = 1.2 C and the energy is equal to 0.5 x 100mF x (12 V)2 = 7.2 J.

When the stopcock is opened, how far up the tube will the water rise? A. 1 m B. 5 m C. 10 m D. 20 m

The answer to this question is C. The water will rise to a height such that the weight (mass multiplied by gravitational acceleration) of the water column equals the atmospheric pressure multiplied by the tube cross-sectional area A. Because m = dv, it follows that 10^3 kg/m^3 x h x A x 10 m/s^2 = 10^5 N/m^2 x A, where h is the height sought. Solving for h yields h = 10^5 N/m^2 / (10^4 N/m^3) = 10m.

What is the resistivity of the best-performing PANI described in the passage? A. 0.002 Ω•cm B. 50 Ω•cm C. 200 Ω•cm D. 500 Ω•cm

The answer to this question is C. This is because resistivity is the inverse of the conductivity, which is 1/5.0 x 10^-3 (Ω•cm)^-1. Thus, the answer is 200 Ω•cm

What is the concentration of hydroxide ion for the solutions with the highest pH that was studied? A. 10-10 B. 10-6 C. 10- 4 D. 10-2

The answer to this question is C. This is because, at the highest pH tested (10) the [H3O+] is 10^-10. That means that [OH-] is 10^-4, because [H3O+] x [OH-] = 10^-14.

Which atom is most likely involved in the coordination of calcium ions found in HRP? A. Hydrogen B. Carbon C. Nitrogen D. Oxygen

The answer to this question is D. Oxygen. This is because an atom must be a Lewis Base to coordinate to calcium ions, and oxygen is the only Lewis basic atom present that has either a partially negative charge or a negative charge. The only other Lewis basic atom present is the Nitrogen which has a partially positive chain and is thus less likely to coordinate calcium ions.

The energy of activation for the reaction described in the passage is given by the energy of: A. the reactants minus the energy of the products. B. the products minus the energy of the reactants. C. the activated complex minus the energy of the products. D. the activated complex minus the energy of the reactants.

The correct answer here is D. The first thing to recognize is that [products] - [reactants] is just the difference in energies between the final and initial states. It is equal to the change in Gibbs Free Energy (delta G) not the activation energy (which is what the question is asking for). Thus, D. would be the correct answer because the energy of activation would be the energy of the activated complex minus the energy of the reactants.

Which of the following is a second period element that is a covalent network solid in its standard state? A. Carbon B. Phosphorous C. Oxygen D. Iodine

The correct answer is A. This is because Carbon is a second period element that is a covalent network solid in its solid state.

Suppose that the railcar passes by a horn that is emitting a sound with frequency f. Which of the following describes the frequency f that the person on the railcar hears? A. f > f before passing the horn, f < f after passing it B. f < f before passing the horn, f > f after passing it C. f = f before passing the horn, f = f after passing it D. f > f before passing the horn, f > f after passing it

The correct answer is A. This is because of the Doppler effect - the frequency that the person on the railcar hears before passing the horn is larger than the actual frequency of the sound emitted, while the person hears a frequency lower than the actual frequency after passing the horn.

What is the balanced equation for the nonproductive reaction when lysine is the substrate? A. H+ + NADPH + O2 → NADP+ + H2O2 B. 2H+ + O2 → H2O2 C. FAD + NADPH + H+ → FADH2 + NADP+ D. 2H2O + O2 → 2H2O2

The correct answer is A. This is because, after considering Reaction 1 it is possible to determine that the nonproductive reaction is between NADPH and O2, with NADP+ and H2O2 as the products and FAD as a regenerated cofactor (not in the equation). Thus, A is the only logical answer.

If no braking occurs, a total of how much power would be required to keep the railcar moving at 40 m/s? A. 16 kW B. 40 kW C. 600 kW D. 800 kW

The correct answer is B. 40 kW. This is because of the formula P = Fv. So, P = 1000 N * 40 m/s so 40,000 W. In other words, 40 kW.

Assume that in the study with the rat tissues, fluid flows at a speed of 0.30 mm/s through a typical capillary opening caused by a burst microbubble. Given this, which of the following is closest to the volume flow rate of fluid passing through the opening? A. 4.5 × 106 μm3/s B. 7.5 × 106 μm3/s C. 1.2 × 107 μm3/s D. 4.5 × 107 μm3/s

The correct answer is B. The relationship is given by 2.5 x 10^4 um^2 x 0.30 mm/s = 7.5 x 10^6 up^3/s.

What is the total mass of D-glucose dissolved in a 2-μL aliquot of the solution used for this experiment? A. 3.6 × 10-7 g B. 1.4 × 10-4 g C. 3.6 × 10-4 g D. 1.4 × 10-1 g

The correct answer is B. The stock solution consisted of 72 g of glucose in 1.0 L of solution (72 ug/uL). Therefore, 2 uL contains 144 ug, or 1.4 x 10^-4 g of the solute.

Based on these data, HCO3- is best categorized as: A. a base since Ka > Kb for this ion. B. a base since Kb > Ka for this ion. C. an acid since Ka > Kb for this ion. D. an acid since Kb > Ka for this ion.

The correct answer is B. a base since Kb > Ka for this ion. For this question a few things are important to know. First, Kw = (Ka)(Kb). Thus, Kw/Ka = Kb. After this it is possible to see that Kb > Ka for HCO3-. And Kb > Ka means that the ion is a base.

Based on the information in the passage and in Figure 1, what effect does epigenetic modification have on iM pH-dependent denaturation? A. Both methylation and hydroxymethylation result in significantly decreased stability because cytosine is more readily deprotonated. B. Both methylation and hydroxymethylation result in significantly decreased stability because cytosine is more readily protonated. C. Only hydroxymethylation results in significantly decreased stability because cytosine is more readily deprotonated. D. Only hydroxymethylation results in significantly decreased stability because cytosine is more readily protonated.

The correct answer is C. This is because the drop in pK of the transition denotes a decrease in stability (remember - small pK = large K = greater instability). DNA unfolding occurs as pH increases, so we can infer that this is due to cytosine deprotonation. Since 5hmC-WT has the lowest pK, hydroxymethylation decreases the stability by increasing the acidity of cytosine.

What is the maximum energy of the UV photons generated by this plasma pencil? (Note: Speed of light is c = 3.0 × 108 m/s; Planck's constant is h = 6.63 × 10-34J•s.) A. 7 × 10-16 J B. 5 × 10-17 J C. 3 × 10-17 J D. 1 × 10-18 J

The correct answer is D. 1 x 10-18 J. This is because the energy of a photon is given by the formula E = hf. The wavelength for UV radiation is given to us and inserting it into the question we get E = hc/lambda = 6.6 x 10^-34 J x (3 x 10^8 m/s)/(200 x 10^-9) = 1 x 10^-18.

At pH 7.5, at what relative rate does the enzyme hydroxylate Compound 1 compared to nonproductively producing H2O2 as a result of interacting with lysine? (Note: Assume equal availability of both substances.) A. 0.50 B. 0.75 C. 1.5 D. 2.0

The correct answer is D. This is because at pH 7.5 the value of kFAD for compound 1 is 2 while the value of kFAD for lysine is 1 (made possible via reading the graph). Thursday the ratio will be 2:1, or D. 2.0.

Which experimental condition is NOT necessary to achieve reliable data for Michaelis-Menten enzyme kinetics? A. Initial velocity is measured under steady state conditions. B. Solution pH remains constant at all substrate concentrations. C. The concentration of enzyme is lower than that of substrate. D. The reaction is allowed to reach equilibrium before measurements are taken.

The correct answer is D. This is because once a reaction reaches equilibrium the Vo measurement will be impossible and the kinetic data will look the same regardless of substrate concentration. Hence, D is not necessary (or reliable) to achieve reliable data for Michaelis-Menten enzyme kinematics.

What is the identity of the substance that has undergone net reduction after the Reaction 1 is complete? A. NADP+ B. FAD C. H2O2 D. O2

The correct answer is D. This is because oxygen is the final acquirer of electrons in the reaction and is therefore reduced.

If the generator-brake system alone were engaged when the railcar was moving, which of the following graphs would most accurately represent the subsequent speed of the railcar?

The correct answer is D. This is because the speed of the car decreases in time such that the decelerating force declines linearly with speed, according to the passage. Because the decelerating force is directly proportional to the deceleration acceleration, it follows that the decelerating acceleration itself declines linearly with speed. Finally, because the decelerating acceleration is rate of change of velocity, or the slope of the velocity vs. time graph, then the slope of the graph must decrease in time. This is only option with a continuously decreasing slope (A. is a constant slope value).

A common column material used in size-exclusion chromatography is dextran, a polysaccharide of glucose. Which type of interaction most likely occurs between proteins and the dextran column material? A. Aromatic B. Hydrophobic C. Salt bridge D. Hydrogen bonding

The correct answer is D. because a polysaccharide of glucose has numerous hydroxyl groups that can hydrogen bond to the polar side chains that are typically exposed on a protein surface.

At which buffer pH would two out of four of the proteins adhere to a cation-exchange column? A. 3.0 B. 7.0 C. 9.5 D. 11

The correct answer to this question is B because a cation-exchange column only binds to positively charged ions (remember caTion = +), which only occurs when the pH is less than the pI (initial). At A there would be four positively charged ions, at C there would be one and at D there would be zero.

What is the correct expression for the ΔG′° for the transition observed in the experiments described in the passage? A. ΔG′° = -RTe([native]/[unfolded]) B. ΔG′° = -RTe([unfolded]/[native]) C. ΔG′° = -RTln([native]/[unfolded]) D. ΔG′° = -RTln([unfolded]/[native])

The correct answer to this question is D. This is because the equilibrium constant for DNA unfolding is Keq = [unfolded]/[native] as the unfolded DNA is considered to be a product. The equation for ΔG′° = -RTlnKeq, thus, the answer will be ΔG′° = -RTln([unfolded]/[native]).

Given that the speed of sound in the rat tissues was 1500 m/s, the wavelength of the ultrasound wave used in the study was closest to: A. 34.5 mm. B. 6.5 mm. C. 1.5 mm. D. 0.65 mm.

The wavelength relationship is given by (1500 m/s)/(2.3 MHz) = 0.65 mm. So the correct answer is D.