








USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam 

Thread Tools  Search this Thread  Display Modes 
#1




enzyme kinetics..
consider a reaction that can be catalyzed by one of two enzymes, A and B, with the following kinetics,
Km (M) Vmax (mmmol/min) A. 5 x 106 20 B. 5 x 104 30 6. At concentration of 5x104 M substrate, the velocity of the reaction catalyzed by enzyme A will be A. 10 B. 15 C. 20 D. 25 E. 30 kindly answer with explanation because i'm just stuck with this....your response will be appreciated.. thankuu 
The above post was thanked by:  
fizA (05212014) 
#2




first of all rule out the last two options because the enzyme cant work beyond it Vmax which is 20.
then rule out the first option bcoz thats the velocity at Km i.e 5 x106 . u r left with B and C now the value 5 x 104 is far above the Km so i m `guessing` the enzyme is working at its Vmax. they dont expect you to solve the complicated calculations on exam but if you want to make sure then solve the problem with lineweaverburk equation and u will get the answer C. 20 
The above post was thanked by:  
#3




Quote:
but i didnt get what is this value: 5 x106?? can you please clear it out? thank you 
#4




Quote:
5x 106 represent the conc of the S= Km for enz A, so at 5x104 definitely the enz will work at its vmax which is 20 so C is the correct answer. 
The above post was thanked by:  
CallingDrAsh (01092014) 
Thread Tools  Search this Thread 
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
cooperative kinetics vs hyperbolic kinetics  shoty  USMLE Step 1 Forum  1  06252013 09:44 AM 
Reaction kinetics question  Casandra  USMLE Step 1 Forum  5  06282012 09:15 AM 
enzyme kinetics  doxorubicin  USMLE Step 1 Forum  1  02032012 07:06 AM 
Enzyme kinetics Q  menatallah Elgohary  USMLE Step 1 Forum  21  08232011 06:41 AM 
Enzyme kinetics: competitive vs. noncompetitive inhibition  jackat1000  USMLE Step 1 Mnemonics  0  01222010 10:15 AM 
