In the conversion of A into D in the fowling biochemical pathway E A , E B, and
ID: 78163 • Letter: I
Question
In the conversion of A into D in the fowling biochemical pathway EA, EB, and EC have the following Km values indicated under each enzyme. If all of the substrates and products are present at a concertation of 10-4 M and the enzymes have approximately the same Vmax which step will be the rate limiting step. (Please explain why)
A------->B--------->C-------->D
EA EB EC
Km: 10-2M 10-4M 10-4M
A. EA
B. EB
C. EC
D. EA and EB
E. EB and EC
Explanation / Answer
Answer: E. EB and EC (As explained below)
The slowest step in a reaction is always the rate-limiting step. So lets find out the step that has the slowest rate.
Rate of reaction for EA = km x EA = 10-2 x 10-2 = 10-4
Rate of reaction for EB = km x EB = 10-2 x 10-4 = 10-6
Rate of reaction for EC = km x EB = 10-2 x 10-4 = 10-6
So, EB and EC is lowest.