bio q 34////////// - mamamia

[ArchivalUser]

Which of the folowing will be unchanged in a Lineweiver-Burk plot of an enzyme with or without a competitive inhibitor?
1/Km
2/Slope
3/x-intercept
4/y-intercept

[ArchivalUser]

4/y-intercept

[ArchivalUser]

gooooooooood

[ArchivalUser]

How does the Y intercept not change? The way I understood it is that:

In comp inhibition -- the Km increases (affecting the X-axis changes), and the Vmax stays the same (so the Y-axis does not change).

In non-comp inhibition or inhibition without a competitive inhibitor -- the Km stays the same (so the Y axis does not change), but the Vmax decreases (therefore the X-axis changes)

So in comp inhibition u see a change in Km (X axis change), and in non-comp inhibition you see a change in Vmax (on the Y-axis).

The question states: Which of the folowing will be UNCHANGED in a Lineweiver-Burk plot of an enzyme WITH OR WITHOUT a competitive inhibitor?

MAYBE I AM JUST READING THE QUESTION THE WRONG WAY? SOMEONE PLEASE HELP ME CLARIFY

[ArchivalUser]

the easiest crude way to remember is competitive crosses each other at y axis and the non competitive crosses each other at x axis. and in both the inhibitors the slope increases!!!
hope it helps

[ArchivalUser]

Thanks Chintoo --

thats basically what I said in my long explination!!! BUT I guess then what I did is understand the question in the wrong way right?

Cause then how can the answer be 4???

[ArchivalUser]

ya u are rite i think u misunderstood the quest.
ru an img happens with me too and then i read explanation and i realise how wrongly i "read" the quest.
here by without they dont mean with non com but without is nothing with the normal ligand.
did u get it or more confused??

[ArchivalUser]

hey chintoo -- thanks for responding. Yes I am an IMG also!! Guess the key is to practice practice and practice............it sucks though -- cause we know all the concepts just questions get tricky once in a while.