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Which of these is exhibiting kinetic energy? a. an archer with a flexed bow |
b. a space station orbiting Earth |
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"Conservation of energy" refers to the fact that _____. a. the entropy of the universe is always increasing |
b. energy cannot be created or destroyed but can be converted from one form to another |
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Chemical energy is a form of _____ energy. a. kinetic |
b. potential |
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In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP? a. redox |
e. cellular respiration |
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Which of these are by-products of cellular respiration? a. glucose, carbon dioxide, and water |
b. heat, carbon dioxide, and water |
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Which of these is ATP? |
3 Phosphate groups attached to a Ribose attached to Adenine |
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What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule? a. dehydration synthesis |
e. hydrolysis |
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AB+CD (reactant~higher on graph) —> AC+BD (product~lower on graph) In this reaction _____. a. entropy has decreased |
e. the products have less potential energy than the reactants |
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AB+CD (reactant~higher on graph) —> AC+BD (product~lower on graph) In this reaction _____. a. the chemical energy of the products is greater than that of the reactants |
c. heat has been released to the environment |
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The following reaction a. exchange |
c. exergonic |
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A(n) _____ reaction occurs spontaneously. a. chemical |
e. exergonic |
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Which of these reactions requires a net input of energy from its surroundings? a. ATP –> ADP + P |
c. endergonic |
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In cells, what is usually the immediate source of energy for an endergonic reaction? a. glucose |
e. ATP |
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The reaction ADP + P –> ATP is a(n) _____ reaction. a. chemical |
e. endergonic |
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The energy for an endergonic reaction comes from a(n) _____ reaction. a. synthesis |
d. exergonic |
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What is the fate of the phosphate group that is removed when ATP is converted to ADP? a. It is acquired by a reactant in a spontaneous reaction. |
d. It is acquired by a reactant in an endergonic reaction. |
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AC+BC (reactant~lower on graph) —> AB+CD (product~higher on graph) This graph illustrates a(n) _____ reaction. a. catabolic |
e. endergonic |
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Select the INCORRECT association. a. exergonic … uphill |
a. exergonic … uphill |
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What is energy coupling? a. the use of energy released from an exergonic reaction to drive an endergonic reaction |
a. the use of energy released from an exergonic reaction to drive an endergonic reaction |
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In general, enzymes are what kinds of molecules? a. proteins |
a. proteins |
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Enzymes work by _____. a. adding a phosphate group to a reactant |
c. reducing EA |
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An enzyme _____. a. can bind to nearly any molecule |
b. is an organic catalyst |
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What name is given to the reactants in an enzymatically catalyzed reaction? a. EA |
b. substrate |
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As a result of its involvement in a reaction, an enzyme _____. a. is used up |
e. is unchanged |
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Graph shows wave line from reactant (higher) to product (lower); "A" refers to highest point on graph, from top of reactant and up What is the correct label for "A"? a. energy of activation |
a. energy of activation |
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Rank these by reaction rate, as measured by the rate of product formation (from the most product formed to the least product formed). reaction catalyzed by enzyme A |
Most product formed —> Least product formed reaction catalyzed by enzyme B—>reaction catalyzed by enzyme A—>uncatalyzed reaction Enzymes lower the activation energy of a chemical reaction. This means that a catalyzed reaction is more likely to proceed than an uncatalyzed reaction, and it forms products more rapidly than an uncatalyzed reaction. |
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Factors that affect enzymes Complete this vocabulary exercise relating to enzymes. Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. |
Hint: A substrate binds at an enzyme’s active site; the enzyme typically recognizes the specific shape of its substrate. A cofactor, such as an inorganic ion or vitamin, may bind to the enzyme and assist in catalyzing the reaction. The reaction environment must be appropriate for catalysis to proceed. An enzyme will denature, or change its shape and lose its biological activity, at too high a temperature or at a pH outside the enzyme’s optimal range. |
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In which region (on graph) does the reaction rate remain constant? a. region A |
c. region C (In region C of the graph, the reaction rate is independent of substrate concentration.) |
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In which region is the enzyme saturated with substrate? a. region A |
c. region C |
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Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction? a. Increase the pH. |
c. Increase the enzyme concentration. If an enzyme is saturated with substrate, and it is operating at optimum pH and optimum temperature, there is very little that can be done except to increase the enzyme concentration. Some enzymes can be activated further by allosteric activators, in which case one might add some activator to the reaction. But otherwise, increasing the enzyme concentration is the only option. |
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Types of enzyme inhibitors Complete this vocabulary exercise relating to the three types of enzyme inhibitors. Drag the words on the left to the appropriate blanks in the sentences on the right. Each word is used only once. |
1. competitive 2. noncompetitive 3. irreversible 4. active site 5. enzyme 6. substrate Competitive inhibitors compete physically and structurally with the substrate for an enzyme’s active site; they can be outcompeted by adding extra substrate. Noncompetitive inhibitors do not compete for the active site, but inhibit the enzyme by binding elsewhere and changing the enzyme’s shape. Irreversible inhibitors bind directly to the active site by covalent bonds, which change the structure of the enzyme and inactivate it permanently. Most medications are enzyme inhibitors of one kind or another. |
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Irreversible inhibition You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme? a. Removing the irreversible inhibitor should get the reaction working again. |
b. The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity. Because they bind directly to the active site by covalent bonds, irreversible inhibitors permanently render an enzyme inactive. Some drugs are irreversible inhibitors, including the antibiotic penicillin (which inhibits an enzyme involved in bacterial cell-wall synthesis) and aspirin (which inhibits cyclooxygenase-2, the enzyme involved in the inflammatory reaction). |
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Reversible inhibition You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again? a. Add more inhibitor to speed up the reaction. |
b. Add more substrate; it will outcompete the inhibitor and increase the reaction rate. Competitive inhibition can be overcome by adding more substrate to outcompete the inhibitor. Many drugs used to treat different medical conditions, including hypertension, are competitive inhibitors. It is fairly easy to make a molecule that is similar in structure to a particular substrate because the known enzyme’s shape can be used as a model of what the molecule needs to look like. It is more difficult to make a noncompetitive inhibitor because it is less obvious what the noncompetitive inhibitor’s shape and structure should be. |
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The image (Figure 1) shows a hypothetical enzymatic pathway with four enzymes, labeled E1, E2, E3, and E4. The enzymes make products, labeled P0, P1, P2, P3, and P4. Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown? a. P0 binds E4 and activates it. |
c. P4 binds E1 and deactivates it. Many enzymatic pathways are regulated by the feedback inhibition model described here. In fact, it is so common that another name for it is end-product inhibition. |
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