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Desperately need biology help!

I am studying biology at home this year, hopefully to take the AS & A2 exams in June. I'm way behind at the moment though and one particular question is really confusing me. Any help would be much appreciated! I'd give you all the rep in the world if possible :biggrin: Thanks

Q:In an investigation of enzyme inhibition, a student made mixtures of substrate and inhibitor in the followin proportions.

Mixture 1: substrate/units =10, inhibitor units =0
Mixture 2: substrate/units =10, inhibitor units = 10
Mixture 3: substrate/units =10, inhibitor units = 20

She added 20cm3 of each mixture to 20cm3 of a standard enzyme solution, and measured the amount of product accumulating over a period of several minutes. The results are shown on the graph below (in the link):
http://tinypic.com/view.php?pic=30c1v9t&s=4

i)what kind of enzyme inhibition is shown by these results? Explain your answer
Surely it could be non-competitive or competitive? I don't understand

EDIT: ON THE GRAPH THE RED LINE SHOULD SAY MIXTURE 1!
Reply 1
Avatar for Char_Devon
Char_Devon
OP
Can anyone help?
I think it is a competitive inhibitor because the amount of product produced from each mixture does eventually reach the same level.
Reply 3
Avatar for Char_Devon
Char_Devon
OP
I have seen examples which suggest if it reaches the same level it is competitive however on the x axis of the graph it would have to say substrate instead of time, surely?
Reply 4
Avatar for hafnium
hafnium
I am confused.
The only difference between competitive and non competitive is that diff. substrate conc. would produces diff rate of enzyme reactions.
substrate conc. is the same in the experiment. cannot distinguish the 2 type of inhibition

can they be after different things?
Reply 5
Avatar for Char_Devon
Char_Devon
OP
hafnium
I am confused.
The only difference between competitive and non competitive is that diff. substrate conc. would produces diff rate of enzyme reactions.
substrate conc. is the same in the experiment. cannot distinguish the 2 type of inhibition

can they be after different things?

I thought the same. I'm wondering if the question is wrong. I will just put that it isn't possible to determineif it is competitive or non-competitive. Thanks
Reply 6
Avatar for Oracle_163
Oracle_163
Char_Devon
I thought the same. I'm wondering if the question is wrong. I will just put that it isn't possible to determineif it is competitive or non-competitive. Thanks


It isn't possible to discern the nature of the inhibitor unless you varied the concentration of the substrate to test it =) Competitive inhibitors will generally not function at high levels of substrate as there are more effective collisions between enzyme and substrate to form ES complexes. On the other hand, non-competitive inhibitors bind to a non-active residue on the enzyme, hence resulting in conformational change of the protein, and permanently reducing the rate of the reaction.

Hope it helps!
Reply 7
Avatar for Char_Devon
Char_Devon
OP
Oracle_163
It isn't possible to discern the nature of the inhibitor unless you varied the concentration of the substrate to test it =) Competitive inhibitors will generally not function at high levels of substrate as there are more effective collisions between enzyme and substrate to form ES complexes. On the other hand, non-competitive inhibitors bind to a non-active residue on the enzyme, hence resulting in conformational change of the protein, and permanently reducing the rate of the reaction.

Hope it helps!


Thankyou - repped :biggrin:
Reply 8
Avatar for Oracle_163
Oracle_163
cheers mate =)

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