MCAT - AAMC Review Study Guide

What is the most likely sequelae in generating the decreased luminal pH following the destruction of antral D-cells in H. pylori infection? A. Decreased production of somatostatin→ decreased inhibition of chief cells→ increased gastric acid production by chief cells B. Decreased production of somatostatin→ decreased inhibition of D-cells→ increased gastric acid production by D-cells C. Decreased production of somatostatin→ decreased inhibition of parietal cells→ increased gastrin production by parietal cells D. Decreased production of somatostatin→ decreased inhibition of G-cells→ increased gastrin production→ increased numbers of mature parietal cells - ANSWERSD A gram-negative bacteria may (be): A. Utilizes Oxygen B. Teichoic acids C. Single lipid bilayer D. Thick peptidoglycan layer - ANSWERSA Which of the following experimental modification will most likely increase the degree of separation between two compounds in vacuum fractional distillation? A. Using a vacuum source that can achieve a lower pressure in the distillation apparatus B. Cooling the condenser with ice water C. Heating the distillation flask at a slower rate D. Using a shorter fractionating column - ANSWERSC How many sodium ions are in the 50.00 mL solution that dissolved 7.15g NáCǑ.10H2O (molar mass 286.14) - ANSWERS3.00E22 The boiling point of glycerine in comparison with that of isopropyl alcohol is: A. more than 10 degrees higher B. less than 10 degrees higher C. more than 10 degrees lower D. less than 10 degrees lower - ANSWERSA Glycerine has 3 OHs What is HCl at room temperature? A. gas B. liquid - ANSWERSA Which of the following properties is associated with glycine as a dipolar ion in aqueous solution? A. High molecular weight B. Low dielectric constant C. Low solubility in water D. High dipole moment - ANSWERSD Which carbon is C1 in a sugar? - ANSWERSThe anomeric carbon (derived from carbonyl in chain format) Compound 2 is larger than compound 1. Is volume of 1.0 g compound 2 greater/equal/smaller than the volume of 1.0g compound 1 at constant pressure? - ANSWERSSmaller. Because the volume of a gas depends only on the number of moles of the gas present and not on the identity of the gas. And according to the ideal gas law: V = (nR/P)/T, more moles of gas means larger volume. And because compound 2 is heavier than 1, there are less of moles of compound 2 in 1.0 g sample than compound 1. Thus the volume of compound 2 is smaller. A sparingly soluble metal hydroxide M(OH)2 has a molar solubility of S mol/L at 25 degree C. Its Ksp value is: - ANSWERS4S^3, because Ksp of AaBb = [A]^a[B]^b. Thus Ksp for M(OH)2 is [M][OH-]^2. Solubility = S mol/L means that [M] = S mol/L, and [OH-] = 2S mol/L, thus Ksp = [S][2S]^2 = 4S^3 As NaOH dissolves in water, the system becomes more/less random? (entropy, delta S) - ANSWERSMore, delta S > 0 Cathod of a galvanic cell is associated with reduction/oxidation? - ANSWERSReduction The cathode of an electrolytic cell is associated with reduction/oxidation? - ANSWERSReduction To prevent body from freezing, some wood frogs perform slow cooling by accelerates glucose release (hyperglycemia). Hyperglycemia promotes cellular dehydration because: A. Glucose accelerates the osmotic work performed by plasma membranes B. Glucose accelerate plasma membrane ion exchange pumps C. Glucose molecules raise the osmotic pressure of the extracellular space D. Glucose molecules are exchanged for water molecules across the plasma membrane - ANSWERSC. Glucose release from glycogen stores raises the osmotic presure of the body fluids and dehydrates cells, protecting them from freezing (only freezes the extracellular space). What is the function of glucagon? - ANSWERSStimulates the conversion of stored glycogen (stored in the liver) to glucose into blood stream 胰增血糖素 Where is glucagon secreted? - ANSWERSalpha cells in pancrease Does hyperglycemia increase/decrease insulin secretion? - ANSWERSIncrease insulin secretion in order to promote glucose uptake (storage) by liver and fat cells What is amitotic division? - ANSWERSA simple splitting of the cell in to half, occurs without formation of spindle fibers and appearance of chromosomes. It does not ensure even splitting of the DNA content To be an effective therapy, and antisense gene that is incorporated into genome that contains the target gene must be: A. on the same chromosome as the target gene but not necessarily physically adjacent B. on the same chromosome as the target gene and must be physically adjacent C. regulated in a similar manner as the target gene D. coded on the same strand of the DNA as the target gene - ANSWERSC. To provide effective therapy, the antisense gene would need to be regulated in a similar manner so that they can be transcribed at the same time, and then bind to each other. Note that here the DNAs are not binding, but the RNAs!!! If oligonucleotides such as mRNA were not degraded rapidly by inracellular agents, which of the following processes would be most affected? A. The coordination of cell differentiation during development B. The production of tRNA in the nucleus C. The diffusion of respiratory gases across the cell membrane D. The replication of DNA in the nucleus. - ANSWERSA. The coordination of cell differentiation during development is extremely sensitive to the timing of mRNA turnover How is increased ADH release related to glomerular filtration rate? - ANSWERSIncreased ADH increases water retention rate, which increases blood pressure and elevates glomerular filtration rate (how much blood passes through the glomeruli each minute). What does aldosterone do and what would happen if an individual has aldosterone deficiency.? - ANSWERSAldosterone stimulates Na+ reabsorption. An individual who has aldosterone deficiency may experience decreased volume and decreased pressure. What is the role of vasodilation in body thermoregulation? - ANSWERSRadiating excess body heat into the environment When the environmental temperature is 45 degree, which of the following organisms will have the highest body temperature? A. Human B. Kangaroo rat C. Camel D. Lizard - ANSWERSD. The question is asking what organism is least able to utilize the cooling mechanism of vasodilation. What is a major contributor to kidney failure? - ANSWERSInsufficient blood flow to the kidneys can cause acute prerenal kidney failure. The kidneys can't filter toxins from the blood without enough blood flow. For example, severe dehydration can contribute to inadequate blood volume for effective filtration and cause kidney failure. What serves as the electron acceptor in production of lactate? A. oxygen B. NAD+ C. pyruvate D. water - ANSWERSC. Pyruvate -- (NADH -> NAD+) --> Lactate by lactate dehydrogenase Pyruvate: CH3COCOOH Lactate: CH3CO(OH)COOH Which other cellular components are likely to be found in E. coli cell membrane? A. proteins and glycolipids B. glycolipids and sterols C. sterols and phospholipids D. phospholipids and proteins - ANSWERSEukaryotes also have membrane lipid innovations that are not found in either Archaea or Bacteria: sterols and sphingolipids. Sterols and glycolipids are essential in all eukaryotic cell membranes, but not in bacteria (e.g., E. coli) What effect would the addition of chloramphenicol (a competitive inhibitor) have on the kinetics of its target enzyme? In terms of Vmax and Km - ANSWERSVmax remains unchanged, Km increases (takes more substrate to achieve 50% Vmax) What mechanism is most likely to responsible for the transport of a unstable, short-half-life transcript to the cytoplasmic membrane after synthesis in E.coli? A. Diffusion across the cytoplasm B. Transport via attachment to the mitotic spindle C. Active transport along cytoskeletal filaments D. Transport from the endoplasmic reticulum in vesicles - ANSWERSC. Prokaryotes do not undergo mitosis Prokaryotes lack nucleus and membrane-bound organelles, including endoplasmic reticulum and mitochondria.. What is the integrated rate law of a 0th order rxn (constant rate)? rate= -d[A]/dt =k - ANSWERS[A]=−kt+[A]₀ concentration of a reactant as a function of time Unit of k is M/sec What is the integrated rate law of a 1st order rxn? rate= -d[A]/dt=k[A] - ANSWERSln[A]=−kt+ln[A]₀ or [A]=[A]₀e^(−kt) Unit of k is 1/sec What is the integrated rate law of a 2nd order rxn? rate= -d[A]/dt=k[A]² = k[A][B] - ANSWERS1/[A]=1/[A]₀+kt Unit of k is 1/[M sec] Phosphatadylethanolamine is a A. glycoprotein B. lipid C. sugar D. protein - ANSWERSB. need long acyl chains What happens to the pH of a soapy solution as a result of the introduction of hardness ions (M2+)? A. The pH increases as [H+] increases B. The pH is not changed since no acid-base reaction occurs C. The pH decrease as [OH-] decreases D. The effect on pH depends on the identity M2+ - ANSWERSC. M²⁺(aq) + 2NaC₁₇H₃₂CO₂ (aq)→ 2Na⁺(aq) + M(CH₃²CO₂)₂(s) [C₁₇H₃₂CO₂]⁻ is a weak base, removal of weak base results in a decrease in pH and a decrease in [OH]⁻ saturation kinetics - ANSWERShigh initial concentration of substrate after which the rate of reaction is independent of further increases in initial substrate concentration, and the enzyme is saturated with substrate. [enzyme-substrate kinetics] Foot-in-the-door technique - ANSWERSconvincing individuals to make a small commitment towards a cause, because this small commitment increases the likelihood for a larger commitment toward the same cause in the future. *Example: encourage ppl to sign a petition to support a commitment. Reference group [social psyc] - ANSWERSany group that individuals use as a standard for evaluating themselves and their own behvaior Primary group [social psyc] - ANSWERSa informal, personal group of close friends and family Secondary group [social psyc] - ANSWERSa formal, impersonal group of acquaintances, colleagues, casual friends etc. Social group - ANSWERSa collection of people with common identity and regular interaction In a case-control study, the dependent variable is temporally ____ to the measurement of the independent variable - ANSWERSPrior. Which weakens the study method positive reinforcement - ANSWERSintroducing a pleasant stimuli that increases the behavioral frequency negative reinforcement - ANSWERSremoving a unpleasant stimuli that increases the behavioral frequency