[MCQs BANK] FOR MORE JUMP ON facebook/eduholics --------------------------------------- 1.Which of the following should be observed with the addition of a catalyst to a chemical reaction? A. the formation of a new product B. the consumption of the catalyst C. the activation energy is lowered D. the decrease in enthalpy Correct Answer: C. the activation energy is lowered A catalyst speeds up a chemical reaction by lowering the activation energy of a reaction. The catalyst is never consumed, nor does it alter the reactants or products. The total enthalpy of the reaction is also not changed from what it would have been without the catalyst. Only the rate at which the reaction occurs and the activation energy is affected. The only answer option that is correct is [C]. _________________________________________________ 2.Enzymes are one of the key proteins in cells and facilitate chemical reactions. How does a typical enzyme catalyze a chemical reaction? A. It eliminates the activation energy of a chemical reaction B. It reduces the activation energy of a chemical reaction C. It provides additional energy to the chemical reaction D. It contains a covalently bound substrate, which is needed for the chemical reaction Correct Answer: B. It reduces activation energy of a chemical reaction Enzymes reduce the activation energy of chemical reactions by binding substrate(s) into energetically favorable orientations. They greatly reduce the activation energy, but do not eliminate it completely. Enzymes are completely reusable—they do not participate in the reaction as a substrate. Even when cofactors are needed for the successful action of the enzyme and though they may be tightly bound, they are not covalently bound to the enzyme. Enzymes do not add additional energy to chemical reactions as heat would, for example. _________________________________________________ 3.What happens to the kinetic energy of a race car if its speed is tripled? A. The kinetic energy increases 3 times its original value. B. The kinetic energy increases 4.5 times its original value. C. The kinetic energy increases 6 times its original value. D. The kinetic energy increases 9 times its original value. Correct Answer: D. The kinetic energy increases to 9 times its original value. Kinetic energy is: KE = (1/2)mv2. The kinetic energy is directly proportional to the square of the velocity (or speed). If the speed is multiplied by 3 (tripled), the KE must be multiplied by 32 = 9. Sidenote, race car spelled backwards is still race car. _________________________________________________ 4.Which of the following statements is NOT true regarding gastrin secretion and function? A. increased production of HCl by parietal cells stimulates gastrin secretion B. gastrin stimulates ECL cells to release histamine C. somatostatin is an inhibitor of gastrin secretion D. elevated gastric pH stimulates G cells to release gastrin. Correct Answer: A. increased production of HCl by parietal cells acts stimulatory on gastrin secretion Gastrin stimulates parietal cells to release HCl. If A were true, then there would be a positive feedback loop where gastrin is stimulating more HCl production, and HCl is stimulating more gastrin production, causing us to burn a hole through our stomach! Increased production of HCl by parietal cells leads to somatostatin secretion, which inhibits the secretion of gastrin. Lastly, an elevated gastric pH (i.e. low amount of acid) would stimulate the G cells to release more gastrin in an attempt to stimulate the parietal cells to release more HCl to bring the acidity back to normal. _________________________________________________ 5.Which of the following is the most accurate statement regarding the theory of Natural Selection? A. Individuals who reproduce in greater numbers are more likely to pass on their genes B. Individuals who have favorable random genetic mutations are not likely pass on their genes C. The environment can only support a finite number of individuals D. Individuals with the most genetic mutations are more likely pass on their genes Correct Answer: C. The environment can only support a finite number of individuals The most accurate statement is C. The statement for A can be true when discussing particular reproductive strategies, however, is not true in all cases. Individuals that are best adapted to their environment will have the greatest chance to pass on their genes, not the ones that produce the most amount of offspring. If an animal produces 1000 offspring and 999 of them die, then the fitness level of that animal is very low, compared to another animal with high fitness that only produces 2 offspring and both live to pass on their genes. Statement B would be correct if it were stated oppositely, since favorable genetic mutations is what creates natural selection. Statement D is not at all accurate regarding the principles of natural selection. For Further MCQs: Visit our page facebook/eduholics #MCAT #ECAT #EDUCATION #MCQS #APTITUDETEST
Posted on: Sat, 26 Jul 2014 13:27:10 +0000
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