MCAT AAMC practice exam Chem Phys with Complete Solutions

MCAT AAMC practice exam Chem Phys with Complete Solutions What quantity of Compound 1 (483.5g) must be provided to prepare 100.00 mL of solution with a concentration equal to Ki (60.3uM)? -Answer-M=mol/v 1 umol=0.000001 moles (1x10^-6) 2.92mg If only [I] is increased, then [ESI] or [EI] increases. This is an example of: A. the Bose-Einstein Principle. B. the Heisenberg Uncertainty Principle. C. the Le Châtelier's Principle. D. the Pauli Exclusion Principle. -Answer-Solution: The correct answer is C. A. The Bose-Einstein Principle states that a collection of atoms cooled close to absolute zero will coalesce into a single quantum state. B. The Heisenberg Uncertainty Principle states that one cannot know both the momentum and position of an object with absolute certainty. C. Le Châtelier's Principle states that in a reversible process, the application of stress to the system will cause the system to respond in a way that will relieve this stress. In this case, the reversible process is E + I forming EI or ES + I forming ESI. In either case, increasing [I] induces stress of the system, and the system relieves that stress by converting I to either more EI or ESI. D. The Pauli Exclusion Principle states that two or more identical fermions, e.g. electrons, cannot occupy the same quantum state. Which structural change to Compound 1 would make it more water soluble? A. Replacing benzene CH with N in the ring B. Replacing C=O with C=CH2 C. Replacing N-N=N with CH-CH=CH D. Replacing NH with NCH3 -Answer-Solution: The correct answer is A. A. Nitrogen in the benzene ring would have a lone pair that could accept a hydrogen bond from water, thus increasing the solubility of the compound. B. Replacing C=O with C=CH2 would decrease the polarity of the compound and make it less water soluble. C. Replacing N−N=N with CH−CH=CH would decrease the polarity of the compound and make it less water soluble. D. Replacing NH with NCH3 removes a hydrogen bond donor, thus decreasing water solubility. In μM•s-1 and μM, what should the approximate values of kcat/KM and Ki be, respectively, when [I] = 180 μM? -Answer-Neither is affected by a change in I, therefore they will stay the same (150 and 60.3). Ki is the equilibrium constant and is never affected by increasing I. What functional group transformation occurs in the product of the reaction catalyzed by Na+-NQR (NADH and ubiquinone)? A. RC(=O)R → RCH(OH)R B. ROPO32- → ROH + Pi C. RC(=O)NHR'→ RCOOH + R'NH2 D. RC(=O)OR'→ RCOOH + R'OH -Answer-Solution: The correct answer is A. A. This is two-electron reduction of a ketone to an alcohol, which is the reaction catalyzed by Na+-NQR. A. This is the reaction catalyzed by a phosphatase. A. This is the reaction catalyzed by a protease or amidase. A. This is the reaction catalyzed by an esterase. What is the chemical structure of a component found in four of the five cofactors (flavins) used by Na+-NQR? -Answer-Solution: The correct answer is B. A. This is the structure of adenine. It is only found in FAD. B. This is the structure of flavin, found in four of the five cofactors used by Na+-NQR. C. This is the structure of ubiquinone. It is a substrate, but not a cofactor. D. This is the structure of histidine. It is an amino acid, not a cofactor. What is the ratio of cation (0.150M) to enzyme (0.75mM) in the spectroelectrochemical experiments described in the passage? A. 1:2 B. 2:1 C. 20:1 D. 200:1 -Answer-0.150M=150mM 150/0.75= 200: 1 (D) The reaction between NADH and ubiquinone is exergonic, but the reaction, when catalyzed by Na+-NQR, does not generate much heat in vivo. What factor accounts for this difference? The reaction catalyzed by Na+-NQR in vivo: A. is more exothermic as a result of the lower activation energy. B. occurs sequentially in several small steps. C. maintains a large separation between the reacting centers. D. is coupled to the movement of a charged particle against a concentration gradient. - Answer-Solution: The correct answer is D. A. This is impossible. Even if it were true, this would make the heat generation larger, not smaller, for the catalyzed reaction. Catalysis does not change thermodynamics. B. By Hess's Law, the heat of reaction will sum and be the same. The fact that the reaction can be broken down into steps will not change the overall thermodynamics. C. This is also impossible. The reactants ultimately must be close together to react. D. The movement of a charged particle against its concentration gradient is energetically costly. Coupling the two processes: the redox reaction between NADH and ubiquinone and the movement of Na+ up a concen