1. At the beginning of an enzyme-catalyzed reaction, during the short period of
ID: 539634 • Letter: 1
Question
1. At the beginning of an enzyme-catalyzed reaction, during the short period of time in which initial velocity measurements are made, the ________ is negligible.
options:
formation of ES from E + P
formation of ES
conversion of ES to E + S
d) Two of the above are negligible under initial velocity conditions.
2. The active site of a certain enzyme contains a serine residue. The enzyme is incubated for a short time with its substrate. A carbonyl group on the substrate forms an acyl-enzyme intermediate that can be isolated and purified, similar to the serine residue in the active site. This information supports ________.
options:
the acid-base catalysis mode
transition state destabilization
a covalent catalysis mode
d) hydrolysis
3. What shape would a graph of relative reaction velocity versus pH likely have for an enzyme in which one ionizable amino acid residue participates in catalysis?
options:
hyperbolic
exponential
sigmoidal
linear
bell-shaped
a)formation of ES from E + P
b)formation of ES
c)conversion of ES to E + S
d) Two of the above are negligible under initial velocity conditions.
2. The active site of a certain enzyme contains a serine residue. The enzyme is incubated for a short time with its substrate. A carbonyl group on the substrate forms an acyl-enzyme intermediate that can be isolated and purified, similar to the serine residue in the active site. This information supports ________.
options:
a)the acid-base catalysis mode
b)transition state destabilization
c)a covalent catalysis mode
a)d) hydrolysis
3. What shape would a graph of relative reaction velocity versus pH likely have for an enzyme in which one ionizable amino acid residue participates in catalysis?
options:
hyperbolic
b)exponential
c)sigmoidal
d)linear
e)bell-shaped
Explanation / Answer
Question 1. At the beginning of an enzyme-catalyzed reaction, during the short period of time in which initial velocity measurements are made, the ________ is negligible.
Answer: a) formation of ES from E + P
Explanation: 1. At the beginning of an enzyme-catalyzed reaction, the enzyme(E) first combines reversibly with its substrate(S) to form an enzymesubstrate complex.
E + S ES
2. In second step, the ES breaks down and yields free enzyme and substrate.
ES E + P
Therefore, at the beginning, the enzymosubstrate complex is getting formed in first step and formation of ES from E and P is negligible.
Question 2: The active site of a certain enzyme contains a serine residue. The enzyme is incubated for a short time with its substrate. A carbonyl group on the substrate forms an acyl-enzyme intermediate that can be isolated and purified, similar to the serine residue in the active site. This information supports ________.
Answer: Covalent Catalysis mode
Question 3. What shape would a graph of relative reaction velocity versus pH likely have for an enzyme in which one ionizable amino acid residue participates in catalysis?
Answer: Bell shaped
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