Bio Feralis' notes Question

[hope_to_match]

---

Members do not see this ad.

"Noncompetetive inhibition – substance inhibits enzyme by binding elsewhere than active site, substrate still binds. "

AP Barrons and Cliffs say that 'binding of either substrate prevents the other from binding'

is this a mistake in the notes?

 

[bigTOOTHguy]

i believe so

 

[hurley]

.

 

[hope_to_match]

I think you may be confusing noncompetitive with uncompetitive. I'm pretty sure uncompetitive inhibition would be outside the scope of the DAT.

In some cases an allosteric substrate might prevent the native substrate from binding, and in other cases the native substrate stills binds but the allosteric substrate modifies the enzyme-substrate complex to be inactive.

i dont think im confusing anything...im just saying that noncompetitive is desribed differently in Feralis' notes and Cliffs/AP Barrons...

 

[FeralisExtremum]

Nope, it's no mistake. I distinctly remember Barron's explanation on noncompetitive inhibition being completely wrong. To clarify on this topic, here's a write-up I did a while back:

On enzymes:

A noncompetitive inhibitor is defined as: "a substance that inhibits the action of an enzyme by binding to the enzyme at a location other than the active site."

Allosteric inhibition is defined as: "a substance that binds to the enzyme and induces the enzyme's inactive form."

These definitions appear extremely similar, so what is the difference, and why do we distinguish between these two concepts? The following is an illustrated example of noncompetitive inhibition:

Note that it does NOT prevent the substrate from binding to the active site, but it still prevents the reaction from completing. Also note that the noncompetitive inhibitor binds at an allosteric site. This is key to understanding the difference: all noncompetitive inhibition is allosteric inhibition, but not all allosteric inhibition is noncompetitive inhibition. Why? Because certain forms of allosteric inhibition can prevent the substrate from binding to the active site, in others words, allosteric inhibition can be noncompetitive or competitive. The above picture is an example of allosteric noncompetitive inhibition. Below is an example of allosteric competitive inhibition:

Another example of allosteric competitive inhibition below:

For contrast, here is standard (non-allosteric) competitive inhibition:

With this in mind, we can now understand why "allosteric inhibition" is a broad concept that does not follow specific Vmax or Km trends like ‘standard' competitive and noncompetitive inhibition do, because it can refer to a variety of conditions under which the substrate may or may not be able to bind to the active site.

It is also worth noting that if you use Barron's AP Biology review book, as of the 3rd edition, it has a completely incorrect definition of noncompetitive inhibitors.

Please let me know if this helped you out, or if I can make it any clearer.

 

[hope_to_match]

Thank you! This is a very good explanation . You cleared up my confusion!

 

[denttal]

Thanks so much! I would not have understood this had I not seen this post!!

 

[Eri3]

one way to remember the difference btw allosteric and competitive inhibition is by noting that allo- means other.

And that illustration is dope.

 

[Faux]

Do we have to worry about campbell 19-21 with these notes?

 

[bigTOOTHguy]

.

 

[FeralisExtremum]

Do we have to worry about campbell 19-21 with these notes?

Some of the material from Campbell's 19-21 with my notes, but not all of it, and definitely not in depth. I need to figure out if I'm going to cover them myself or just attach an extra set of notes I found that covers those chapters.

This really threw me off now, can anyone dumb it down for me ?

basically allosteric just constitutes something that binds elsewhere, does this then mean that competitive just doesnt allow binding and non competitive just inhibits the enzyme is some way ?
^ I think i caught on halfway through typing this, if someone could confirm this or help me that would be great.

Allosteric means that the inhibitor binds elsewhere on the enzyme, and non-allosteric means that it binds directly at the active site.

Competitive means that it prevents the substrate from binding to the enzyme. Non-competitive means that it does not prevent the substrate from binding to the enzyme (but still prevents the reaction from being completed). In table form:

 

[aznnytezx]

Some of the material from Campbell's 19-21 with my notes, but not all of it, and definitely not in depth. I need to figure out if I'm going to cover them myself or just attach an extra set of notes I found that covers those chapters.

The extra set of notes sound great. When will part 2 of the notes be done? I don't mind about the DATQVAULT & Destroyers part. I think that shouldn't be on there because that makes practice through memorization.

 

[FeralisExtremum]

The extra set of notes sound great. When will part 2 of the notes be done? I don't mind about the DATQVAULT & Destroyers part. I think that shouldn't be on there because that makes practice through memorization.

I'll upload that extra set of notes soon. Regarding version 2 of my own, I plan on doing roughly ~10 pages of my notes a day, so I can either upload the changes in increments every day for this week (which can kind of be tedious) or I can upload the entire revision at the end of the week.

As far as including material from Destroyer and DATQvault - I completely agree that including an answer to a question straight up is pretty useless, because then all you've learned is how to answer a single specific question that isn't likely to show up on your DAT anyway. What I try to do is review all the answer choices and if any of them include material that I am unfamiliar with, I do a bit of research and then concisely summarize it in my notes (for example, one of the answers to a Qvault question was nuclear lamina, and I had never seen that before, so I looked it up and included it). I'll try to use these sources as an exposure to more topics, and not necessarily just the parts relevant to the right answer.

 

[bigTOOTHguy]

.