AAMC Sample Test C/P Questions and Answers 2023

AAMC Sample Test C/P Questions and Answers 2023 Agonist -a molecule that, by binding to a receptor site, stimulates a response. -something that acts in a similar fashion to something else 2. How many stereoisomers of Compound 1 exist? A.8 B.16 C.32 D.64 The answer is C. I got it wrong and put B because I incorrectly counted 4 chiral centers when there is 5. 2^n rule. 5. Which image best illustrates the electric field lines between the inside of an axon and the surrounding extracellular solution? This question relies on prior knowledge of the charge distribution in an axon, where the interior is negatively charged and the exterior is positively charged. Electric field lines move from positive to negative charges, as reflected by B. Conductivity and resistivity conductivity is the reciprocal of resistivity. decreased conductivity means increased resistivity. an insulating material will cause increased resistivity. myelin sheath decreases capacitance, increases resistivity. The purpose of myelin sheath is to assist with the propagation of nerve impulses. It functions in this capacity by insulating the internal cytosol from the extracellular fluid. When the nodes of Ranvier open in response to stimulus, the resulting depolarization can only be transmitted along the axon since the myelin sheath is insulating. 7. Channel X transmits only the smallest substances dissolved in the extracellular fluid through the axon membrane. Which substance does Channel X transmit? A.Proteins B.Sodium ions C.Potassium ions D.Chloride ions The question asks which of the choices is the smallest. Choice A, proteins, can be immediately eliminated. Potassium ions (choice B) can be eliminated as K is one row below Na on the periodic table. Within the same row, a cation (like Na) will always have a smaller radius than an anion. Since a chloride ion is an anion, choice D can be eliminated (Na+ = 102 pm; Cl- = 181pm). 8. What is the closest distance the electrodes used in an NCV test can be placed on a nerve in order to measure the voltage change as a response to the stimulus? A.0.01 m B.0.1 m C.1.0 m D.10 m The graph in figure 2 shows that the width of the action potential peak of the response of a nerve cell to stimulus is about 1 millisecond. The passage also tells us that a nerve cell pulse travels at 100 m/s. Thus the minimum distance between electrodes measuring the voltage change is given by the kinematic relation distance = rate × time = 1 ms × 100 m/s = 0.1 meters. 9. What information about an axon is required to calculate the current associated with an NCV pulse? To calculate the current through an axon, use Ohm's law, I = V/R. Potential is needed, eliminating choice A. Table 1 provides resistance per unit length, which is not the same thing as resistivity (the AAMC solution to this question is erroneous in that respect), but using a combination of either resistance per unit length or resistivity (with units of resistance × length) and length can yield resistance R. Though radius also has units of length, the product of conductivity and radius or the quotient of resistivity and radius does not give resistance along the direction of current flow of an axon, eliminating choices B and C. Electronegativity a compound is basic when the metal has low electronegativity a compound is basic when the nonmetal has high electronegativity triacylglycerol have carboxyl groups and ester linkages Prostaglandins -A group of bioactive, hormone-like chemicals derived from fatty acids that have a wide variety of biological effects including roles in inflammation, platelet aggregation, vascular smooth muscle dilation and constriction, cell growth, protection of from acid in the stomach, and many more. -have a 5 member ring and a bunch of OH's 16. Addition of which disaccharide to a solution of Ag2O in NH3(aq) will NOT result in the deposition of shiny silver mirror on the walls of the reaction vessel? The deposition of silver metal represents a reduction of silver ions (gain of electrons). Therefore, the question is asking which of the answer choices is not a reducing sugar. Reducing sugars contain either aldehydes or hemiacetals (which become aldehydes during mutarotation). Of the four answer choices, only choice D contains no hemiacetal functionalities. In choices A-C there is a hemiacetal on the far right hand side of each compound, as depicted for cellobiose below, making them reducing sugars. The answer to this question is D because sucrose does NOT possess a hemiacetal functional group, will NOT undergo mutarotation, and will NOT be oxidized by Ag+. Saccharides undergo mutarotation if they are capable of ring-opening. The process of ring-opening occurs at a hemiacetal group, and the intermediate is an aldehyde. Such sugars are termed "reducing sugars" as a result of their ability to be oxidized by Ag+. Km The expression for KM is the same as a dissociation constant under conditions where product formation is the rate-limiting step. 22. What type of reaction is Reaction 1? A.Oxidation/reduction B.Lewis acid/Lewis base C.Double replacement D.Ionization it can be seen that Mg is oxidized (0 to +2) while H is reduced (+1 to 0). This means that the reaction is an oxidation/reduction reaction, and choice A is correct. A Lewis acid/Lewis base reaction is one in which an electron pair on one reactant (the base) is donated to the other (the acid) in the formation of a new compound (e.g., Cl- + BCl3 → BCl4-). In these reactions the charge state of the atoms do not change (eliminate choice B). Double replacement, often called ion exchange, reactions are transformations in which ionic compounds simply switch anions and cations (e.g., CsCl + NaI → CsI + NaCl). Again, in these reactions no oxidation 6 state changes occur (eliminate choice C). An ionization reaction generally describes the dissociation of a neutral compound into its constitutive ions (e.g., HCl → H+ + Cl-), but the oxidation states of the atoms in the compounds remain unchanged before and after the reaction (eliminate choice D). 23. Suppose that at the end of Reaction 1 the level of the aqueous solution were 26 cm higher inside the buret than outside. Compared to ambient pressure, the pressure of the gas inside the buret would be: A.lower. B.the same. C.2 times greater. D.26 times greater. The answer to this question is A because the level of the liquid inside is higher than outside which results from the fact that the air pressure outside is higher than the pressure inside. Pressure builds on the inside by raising the liquid level. When the sum of the inside air pressure plus liquid pressure equals the outside air pressure, the liquid level stops rising (attains equilibrium). 26. The average human body contains approximately 5 liters of blood. If the blood has a density of 1060 kg/m3, what is the total mass of blood in the average human? (Note: 1 L = 1000 cm3.) A.0.212 kg B.0.530 kg C.5.30 kg D.10.6 kg This is a dimensional analysis question. The given data is that the human body contains about 5 L of blood, and that the density of blood is about 1060 kg/m3. Also given is that 1 L = 1000 cm3. From this we can say that 5 L = 5000 cm3. 1m3 = 1 m × 1 m ×1 m = 100 cm × 100 cm × 100 cm = 106 cm3 Therefore, the density of blood is (1060 × 10-6) kg/cm3. Then, 5000 cm3 × (1060 × 10-6) kg/cm3 ≈ 5000 cm3 × (0.001) kg/cm3 = ~5 kg The best answer is choice C. 27. An ultrasound examination could show the motion of a fetus. In order to image this motion, the ultrasound examination devices requires what minimal information? A.The speeds of the sound and of the moving object. B.The speed of the sound, and the frequencies of the sound waves emitted and observed. C.The speeds of the sound and of the moving object, and the frequencies of the sound waves emitted and observed. D.The speeds of the sound and of the moving object, and the frequencies and wavelengths of the sound waves emitted and observed. One way to think about this question is to consider what can be directly measured versus what the ultrasound probe is designed to discover indirectly. The purpose of the probe is to see motion in the fetus, so knowing the speed of the moving object beforehand is unrealistic: that's what it is trying to find! This eliminates choices A, C, and D. Choice B is correct because the Doppler shift relates frequencies at the source and the detector (which was the original source prior to frequency shifting upon reflection off of the fetus), the speed of sound, and speeds of the source 7 and detector (in this case, the same object, again due to reflection). Knowing the first three of these determines the fourth. principle quantum number approx radial size of electron cloud, PE of electron the principal quantum number n is most closely associated with the potential energy of the electron. Since potential energy is proportional to the square of the distance of two oppositely charged particles by Coulomb's Law, it is also true that n is associated with the radial "size" of the electron cloud. 30. Metal ions present in plasma are expected to: A.increase the amount of CPFX bound to BSA. B.decrease the amount of CPFX bound to BSA. C.decrease the amount of free CPFX found in plasma. D.have little effect on the amount of bound CPFX. Table 2 gives the relevant data for the binding of CPFX to BSA in the presence of various metal ions. The legend states that K0 is the binding constant of CPFX-BSA in the absence of metal ions. Since the Ka/K0 ratio is less than 1.0 in all cases, the presence of metal ions decreases the binding of CPFX to BSA (choice B is correct and choices A and D are wrong). Note that a Ka/K0 ratio of 1.0 would occur if binding to BSA was the same in the presence or absence of metal ions, and it would be greater than 1.0 if binding to BSA was increased in the presence of metal ions. If less CPFS is binding to BSA, then the amount of free CPFX in plasma should increase (choice C is wrong). 33. Sites I and II are most likely lined with the side chains of which amino acids? A.R and L B.E and Y C.D and E D.D and H The passage states that the ligands for the binding sites tend to be "hydrophobic with anionic features", thus amino acids in Sites I and II are likely to be hydrophobic and carry positive charges (hydrophobic amino acids will interact favorably with hydrophobic ligands, and positivelycharged amino acids will interact favorably with negatively-charged, anionic ligands). R (arginine) is positively charged and L (leucine) is hydrophobic (choice A is correct). E (glutamic acid) and D (aspartic acid) are typically negatively charged (choices B, C, and D are wrong). Note that Y (tyrosine) is hydrophilic and H (histidine) is sometimes charged and sometimes not. temperature and resisitivity linearly proportional? heat capacity mass x specific heat 39. Mevalonate exists in equilibrium with Compound X in aqueous solution. What is the structure of Compound X? Ring closing reactions, especially those forming the thermodynamically favored six-membered rings, are very common. Below is a depiction of the reaction that may be expected to occur with mevalonic acid. Choices C and D depict thermodynamically unfavorable reactions. Peroxides (choice C) and fourmembered rings (choice D) are both very high energy species, and unlikely to form from a stable molecule such as mevalonic acid. Choice B depicts a reduction reaction, which does not occur. C=C double bond IR cm-1 region Aromatic IR C-H C-C water achiral enzymes are routinely chiral, built to be able to synthesize chiral compounds. myopia diverging lens will spread out the light before it reaches the lens of the eye which will cause light to focus on a point closer to the retina. Myopia is treated with diverging lenses, because the power of the eye's cornea and lens system is too high, so a negative power lens is required to lower it appropriately. Put another way, the myopic eye focuses light from distant objects prior to its reaching the retina, and the addition of a diverging lens moves the focal point further back to reach the retina. 43. One method of isolating polypeptides and proteins from aqueous extracts is freeze drying. The aqueous solution of the polypeptide or protein is frozen. What procedure can be used to remove the water from the frozen sample? A.Sublimation under reduced pressure B.Distillation using steam C.Extraction with organic solvent D.Addition of magnesium sulfate The goal of most polypeptide and protein extraction methods is to keep the protein from denaturing. Sublimation, the phase change of water from solid to gaseous state, eliminates the water from the sample without raising the temperature and possibly denaturing the protein (choice A is correct). Steam distillation would increase the temp and damage the protein (choice B is wrong), and addition of organic solvents or magnesium sulfate could also denature the protein (choices C and D are wrong).