Chap 8 mastering – Flashcards
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Which of the following correctly states the relationship between anabolic and catabolic pathways?
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Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
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Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?
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Organisms acquire energy from, and lose energy to, their surroundings.
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Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics?
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To obey the first law, the crops must represent an open system.
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Which of the following states the relevance of the first law of thermodynamics to biology?
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Energy can be freely transformed among different forms as long as the total energy is conserved
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Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?
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The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.
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According to the second law of thermodynamics, which of the following is true?
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The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.
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If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
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Energy input into the organism must be occurring to drive the decrease in entropy.
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Which of the following has the most free energy per molecule?
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a starch molecule.
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Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous?
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ΔG because In any spontaneous process, the free energy of a system decreases.
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If, during a process, the system becomes more ordered then___
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ΔS is negative
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When one molecule is broken down into six component molecules, which of the following will always be true?
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ΔS is positive
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From the equation above it is clear that
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a decrease in the systems total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change.
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An exergonic reaction is a chemical reaction that
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releases energy when proceeding in the forward direction
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which of the following reactions would be endergonic.
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glucose + fructose > sucrose
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Molecules A and B contain 110kcal/mol of free energy, and molecules B and C 150kcal/mol of energy. A and B are converted to C and D. What can be concluded?
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the reaction that proceeds to convert A and B to C and D is endergonic. the products are more organized than the reactants.
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Which of the following determines the sign of ΔG for a reaction?
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the free energy of the reactants and products.
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Metabolic pathways in cells are typically far from equilibrium.. Which of the following processes tends to keep these pathways away from equilibrium.
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The continuous removal of the pruducts of a pathway to be used in other reactions and an input of free energy from outside the pathway.
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The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients.
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proton movement against a gradient of protons.
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In general, the hydrolysis of ATP drives cellular work by ___
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releasing free energy that can be coupled to other reactinos
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Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell AGAINST the ion's concentration gradient?
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This is an example of energy coupling
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Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because
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the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP.
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When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations?
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In the cell, the hydrolysis of ATP is coupled to other endergonic reactions
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Which of the following best characterizes the role of ATP in cellular metabolism?
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the free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
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the formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways.
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the hydrolysis of ATP.
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a chemical reaction is designated as exergonic rather than endergonic when
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the potential energy of the products is less than the potential energy of the reactants.
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which of the following is changed by the presence of an enzyme in a reaction?
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the activation energy.
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What do the sign and magnitude of the delta G of a reaction tell us about the speed of the reaction?
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neither the sign nor the magnitude of delta G has anything to do with the speed of the reaction
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how do enzymes lower activation energy
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by locally concentrating the reactants
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which of the following statements about enzymes is true
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enzymes speed up the rate of the reaction without changing the delta G for the reaction
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which of the following statements about enzyme function is correct?
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enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output
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A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that __________.
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there is too little activation energy available
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which of the following statements about enzymes is INCORRECT?
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an enzyme is consumed during the reaction it catalyzes
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which of the following statements about the active site of an enzyme is correct?
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the active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.
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what is meant by the induced fit of an enzyme
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the enzyme changes its shape slightly as the substrate binds to it.
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which of the folowing statements correctly describes the role or roles of heat in biological reactions
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heat from the environment is necessary for substrates to get over the activation energy barrier and kinetic energy of the substrates is increased as the amount of heat in the system is increased
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Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. Which of the following would lead to a faster conversion of substrate into product under these saturated conditions?
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an increase in concentration of enzyme and increasing the temperature by a few degrees.
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which of the following environments or actions would NOT affect the rate of an enzyme reaction?
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none are correct
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enzyme activity is affected by pH because
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high or low pH may disrupt hydrogen bonding or ionic interaction and thus change the shape of the active site.
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which of these statements about enzyme inhibitor is true?
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the action of competitive inhibitors may be reversible or irreversible
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Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation
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Succinylcholine must be a competitive inhibitor with acetylcholine.
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the process of stabilizing the structure of an enzyme in its active form by binding of a molecule outside the active site is example of
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allosteric activation
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which of the following statements about allosteric proteins is/are true
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they are senstive to environment conditions. they are acted on by inhibtors. they exist in active and inactive conformations.
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the binding of an allosteric inhibitor to an enzyme cause the rate of product formation by the enzyme to decrease. which of the follwoing best explains why this decrease occurs
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the allosteric inhibitor cause a structural change in the enzyme that prevents the substrate from bindinng at the active site.
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Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true?
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high levels of ADP result in allosteric activation of catabolic pathways.
