Questions
1. Fill-in-the-Blank Enzy mes accelerat e the rate of a ch emical reaction by _ _________________ the free en ergy of
activation of the reaction.
2. An enzy me which loosely binds substrate will have a _ _________________ level of efficiency .
3. Org anic co factors are referred to as __________________.
4. A reaction can occur spontaneously only if G is ____ ______________.
5. Wh en G for a system is zero , the system is at __________________.
6. An enzy me which has b een stripped o f the small molecules needed for activity is called an
__________________.
7. The total change of free en ergy in a reaction dep ends o n __________________ and
__________________.
8. Competitive inhibitors which mi mic the substrate while in the transition state are called
__________________ inhibitors.
Multiple-Choice Questions
9. Wh at is the co mmon strategy by which catalysis occurs ?
A)
increasing the prob ability of product formation
B)
shifting the reaction equilibrium
C)
stabilization of transition state
D)
All of the abov e.
E)
None of the above.
10. An en zyme will specifically bind its substrate b ecause of:
A)
a high number of exclusively hydrophilic amino acids at the active site.
B)
a high number of hydrophobic amino acids in the center of the protein.
C)
a large numb er of weak interactions at the active site.
D)
additional nonprotein cofactors.
E)
None of the above.
11. A cofactor is best d efined as:
A)
another protein.
B)
a covalently bound inorganic molecule.
C)
a small molecule that holds the substrate in the active si te.
D)
a molecule responsible for most of the catalytic activity of the enzy me.
E)
None of the above
12. Which of the following is tru e?
A)
Enzy mes force reactions to proceed in only one direction.
B)
Enzy mes alter the equilibrium of the reaction.
C)
Enzy mes alter the standard free en ergy of the reaction.
D)
All of the abov e.
E)
None of the above.
13. The rate of a reaction, or ho w quickly a reaction will proceed, is best determined by:
A)
S
B)
G
C)
G
D)
H
E)
None the of above.
14. A graph o f product v ersus time (as in Figure 6.2 in you r textbook) for an enzy me is d etermined
to be hyperbolic. Why does the amount of product level off as time increases?
A)
The reaction has reached equilibrium; that is, the forward and revers e reactions are
occurring at a fixed rate.
B)
There is a product inhibition of the enzyme.
C)
The reaction runs out of reaction materials.
D)
The enzy me has finished accelerating the reaction.
E)
None of the above.
Ans: A
15. The free energy of activation is:
A)
the amount o f ch emical energy av ailable in the transition state.
B)
the difference in free energy bet ween the substrate and the product.
C)
the free en ergy g ained by adding a catalyst.
D)
the difference in free energy bet ween the transition state and the substrate.
E)
All of the abov e.
16. The molecular structure that is short-lived and neither substrate nor product is known as the:
A)
substrate analog.
B)
transition state.
C)
free-energy stabilization state.
D)
catalysis state.
E)
equilibrium intermediate.
17. Riboflavin is a water-soluble org anic substance that is not synthesized by humans .
Metabolically, it is chemically converted into a substance called flavin adenine dinucleotide,
which is required by succinate dehydrogenas e. Which o f the follo wing statements is most
correct ?
A)
Riboflavin is a coenzy me.
B)
Flavin adenine dinucleotide is a vitamin.
C)
Succiniate d ehydrogenase is a coenzy me.
D)
Flavin adenine dinucleotide is a coenzy me.
18. The active site of an en zyme:
A)
is a series of amino acids which bind the enzy me.
B)
is a linear sequence of amino acids that react with each other.
C)
binds covalently to the substrate.
D)
allows water to enter into the active site and thereby sol vate the substrate.
E)
None of the above.
Short-Answer Questions
19. Ho w do enzy mes catalyze reactions?
Ans:
20. Ho w is the substrate bound to the active site?
Ans:
21. Wh at are transition-state analogs?
Ans: