2.4 Study Guide Flashcards
Which is FALSE about enzymes?
a. They lower the activation energy for product formation
b. They alter the equilibrium of product formation
c. They increase the rate of product formation
d. They interact specifically with substrates and transition states
e. None of the above
They alter the equilibrium of product formation
An enzyme brings together the ester of one substrate molecule with a carboxylate from a second
substrate molecule in the active site to promote formation of an anhydride. What is this an example of?
a. Providing a catalytically active group to increase rate of reaction
b. Reducing the entropy of a reaction
c. Binding of transition states with higher affinity than substrates
d. None of the above
e. All of the above
Reducing the entropy of a reaction
Which is FALSE about substrate transition states?
a. They participate in many weak interactions within the enzyme active site
b. The many weak interactions causes a decrease in free energy
c. They are less complementary to the active site than the substrate
d. They are very unstable
e. None of the above
They are less complementary to the active site than the substrate
Which of these functional domains in chymotrypsin is responsible for determining the position at which
the susbtrate polypeptide is cleaved
a. The catalytic domain
b. The oxyanion hole
c. The substrate binding pocket
d. The specificity pocket
e. None of these domains
The specificity pocket
Which is a function of serine in the chymotrypsin catalytic triad?
a. Forms a nucleophilic alkoxide ion that attacks the peptide substrate
b. Stabilizes the positively charged His residue
c. Deprotonates water
d. Donates a proton to the amino leaving group
Forms a nucleophilic alkoxide ion that attacks the peptide substrate
Order these steps of chymotrypsin enzymatic activity properly:
1. One product diffuses away, the other forms a second tetrahedral intermediate
2. A negatively charged tetrahedral acyl-enzyme intermediate is formed
3. Collapse of the intermediate displaces the substrate-enzyme covalent bond
4. Collapse of the intermediate causes the substrate peptide bond to be cleaved
5. Attack by an alkoxide ion forms a covalent bond between the substrate and the enzyme
a. 5, 2, 4, 3, 1
b. 5, 2, 4, 1, 3
c. 2, 5, 4, 3, 1
d. 2, 5, 4, 1, 3
e. 3, 4, 1, 2, 5
5, 2, 4, 1, 3
1. Attack by an alkoxide ion forms a covalent bond between the substrate and the enzyme
2.A negatively charged tetrahedral acyl-enzyme intermediate is formed
3. Collapse of the intermediate causes the substrate peptide bond to be cleaved
4.One product diffuses away, the other forms a second tetrahedral intermediate
5. Collapse of the intermediate displaces the substrate-enzyme covalent bond
A peptide chain is composed of the following sequence: ASIWVLRTPIQ. Where would it be cut by
trypsin?
a. Between the I and the W
b. Between the W and the V
c. Between the L and the R
d. Between the R and the T
e. Trypsin would not cut this peptide
Between the R and the T
Which is TRUE about enzyme inhibitors used as pharmaceuticals?
a. They are highly reactive
b. They are made only by plants
c. They only target proteases
d. They bind with high affinity to active sites and permanently block catalysis
e. All of the above
They bind with high affinity to active sites and permanently block catalysis
Why don’t antiviral protease inhibitors that target HIV detrimentally affect our protease enzymes?
a. The antivirals are highly unstable in vivo
b. HIV proteases have different cleavage specificity than our enzymes
c. They are not tetrahedral intermediate mimics
d. HIV proteases are inherently more fragile than our proteases
e. They do target our protease enzymes
HIV proteases have different cleavage specificity than our enzymes
Zanamivir and related anti-Influenza drugs act by:
a. Promoting viral particle release from host cell membranes
b. Mimicking sialic acid
c. Activating neuraminidase
d. Binding to viral DNA
Mimicking sialic acid
The anti-trypanosomal drug DFMO:
a. Is an ornithine mimic
b. Has electronegative fluorine groups that perturb electron flow during catalysis
c. Disrupts DNA packaging by inhibiting polyamine synthesis
d. Is a suicide inhibitor of both mammalian and trypanosomal ornithine decarboxylase
e. All of the above
All of the above
How do plants protect themselves from caterpillars?
a. They make ornithine decarboxylase inhibitors
b. They make protease inhibitors that inhibit caterpillar proteases that cleave the peptide bond
between Phe and Pro
c. They disrupts caterpillar DNA packaging by inhibiting polyamine synthesis
d. They inhibit caterpillar digestion using inhibitors of serine proteases
They inhibit caterpillar digestion using inhibitors of serine proteases
