Download Ch. 5 Enzyme Review

Enzyme Chapter Review
Name ___________________
Date ___________________
Period ________
Multiple Choice: Read each questions carefully. Choose the one best answer and circle the letter of
your choice.
1. Which statement regarding enzyme function is true?
a. Higher temperatures allow greater contact between enzymes and substrates; therefore, the
higher the temperature the better the enzyme will function.
b. Enzymes cannot function at a pH lower than 6.
c. Most coenzymes are inorganic substances such as ions of iron or potassium.
d. Excessive salt ions can cause an enzyme to denature.
e. All of the above.
2. Consider a hypothetical metabolic pathway for the synthesis of the amino acid arginine: precursor A
intermediate B arginine. Each reaction is catalyzed by a different enzyme. This metabolic pathway is
controlled by feedback inhibition with arginine inhibiting the conversion of precursor A to intermediate
B. In this case, arginine almost certainly acts as a _____ of the first enzyme in the pathway.
a. substrate
b. competitive inhibitor
c. catalyst
d. cofactor
e. none of the above
3. According to the second law of thermodynamics, which of the following is true?
a. The total amount of energy in the universe is constant.
b. Energy conversions increase the order in the universe.
c. The ordering of one system depends on the disordering of another.
d. The entropy of the universe is constantly decreasing.
e. All reactions produce some heat.
4. Which one of the following is an example of the second law of thermodynamics?
a. The aerobic respiration of glucose generates heat.
b. All types of cellular respiration produce ATP.
c. CO2 is exhaled as a by-product of aerobic respiration.
d. Photosynthesis enables plants to create energy from sunlight.
e. Energy is stored during the Calvin cycle.
5. The first law of thermodynamics ____________.
a. states that energy is neither created nor destroyed
b. deals with entropy
c. deals with heat content
d. states that entropy spontaneously increases
e. predicts the direction of a reaction
6. A reaction is designated as exergonic rather than endergonic when ___________.
a. activation energy exceeds net energy release
b. activation energy is necessary
c. no kinetic energy is released
d. the potential energy of the products is less than the potential energy of the reactants
e. it absorbs more energy
J. Haut. Ch. 5 Review. Pre-AP Biology 2006
7. A cell uses energy released by ____ reactions to drive the ____ reaction that makes ATP. Then it uses
the energy released by the hydrolysis of ATP, an ____ reaction, to do various kinds of work in the cell.
a. exergonic…exergonic…endergonic
b. endergonic…exergonic…endergonic
c. exergonic…endergonic…exergonic
d. endergonic…endergonic…exergonic
e. exergonic…endergonic…endergonic
8. The mechanism of enzyme action is _____.
a. to create an energy barrier between substrates
b. to lower the energy of the activation of a reaction
c. to change the direction of thermodynamic equilibrium
d. to change endergonic into exergonic reactions
e. to allow substrates to move more freely in solution
9. If the tertiary structure of an enzyme is changed _____.
a. its substrate may not fit properly in the active site
b. it will be missing one of its polypeptides
c. the helical coil will be stretched out
d. the product of the reaction will be a different molecule
e. its substrate will bond covalently with the wrong part of the molecule
10. Why does heating interfere with the activity of an enzyme?
a. It kills the enzyme.
b. It changes the enzyme’s shape.
c. It decreases the energy of substrate molecules.
d. It causes the enzyme to break up.
e. It decreases the chance that the enzyme will meet a substrate molecule.
11. An enzyme is specific. This means
a. it has a certain amino acid sequence.
b. it is found only in a certain place.
c. it functions only under certain environmental conditions.
d. it speeds up a particular chemical reaction.
e. it occurs in only one type of cell.
12. A molecule that has the same shape as the substrate of an enzyme would tend to
a. speed metabolism by guiding the enzyme to its substrate.
b. speed metabolism because it would also be a catalyst.
c. speed metabolism by acting as a cofactor for the enzyme.
d. save the cell energy by substituting for the substrate.
e. slow metabolism by blocking the enzyme’s active site.
13. Some enzymes involved in the hydrolysis of ATP cannot function without help of sodium ions.
Sodium in this case functions as
a. a substrate
b. a cofactor
c. an active site
d. a noncompetitive inhibitor
e. a vitamin
J. Haut. Ch. 5 Review. Pre-AP Biology 2006
14. In which of the following do both examples illustrate kinetic energy?
a. Positions of electrons in an atom…a ball rolling down hill
b. Heat…arrangement of atoms in a molecule
c. A rock resting on the edge of a cliff…heat
d. A ball rolling down a hill…heat
e. Light…arrangement of atoms in a molecule
15. Which of these statements about enzyme inhibitors is true?
a. A competitive inhibitor binds to the enzyme outside the active site.
b. The action of competitive inhibitors may be reversible or irreversible.
c. A noncompetitive inhibitor does not change the shape of the active site.
d. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known
as positive feedback.
e. Antibiotics and pesticides generally do not act on enzymes, but rather affect the genetic
code of their victims.
Essays: Answer the following questions using complete sentences.
16. Most enzyme-catalyzed chemical reactions in humans occur most readily around body temperature,
37°C. Why do these reactions slow down at lower temperatures? Why do these reactions slow down at
much higher temperatures?
17. Which contains more potential energy, a large, complex molecule like a protein, or the smaller amino
acid subunits of which it is composed? Explain why.
18. Is the joining of amino acids to form a protein an exergonic or endergonic reaction? Explain.
19. What forces and bonds maintain the 3-D folded shape of a protein molecule? How does this
relate to the sensitivity of proteins to changes in their environment?
J. Haut. Ch. 5 Review. Pre-AP Biology 2006