BIO question

[299678]

Advertisement - Members don't see this ad

Which of the following functions are performed by a receptor to initiate proper reaction cascade?
I. allows for a high degree of specificity
II. amplifies the incoming signal
III. causes the modification of binding ligand
a) I
b) I and II
c) II and III
d) I, II, III

Receptor properties are important to proper metabolic function because they provide a high degre of specificy for particular ligand (hormone, neurotransmitter). This makes it possible for a hormone to be secreted at one site in the body and have very specific effects on a distant target organ with a proper receptor. However, the receptor neveer modifies the ligand because doing so would destroy the ligand specificity

a receptor also amplifies the stimulating signal. This is why hormone that are present in extremely minute concentration can exert such a powerful control over bodily processes

answer is b) I and II

By using the same principle above described, I am wondering about the how enzyme work based on induced fit theory, does enzyme change the conformation of substrate?

 

[sfoksn]

yes, enzyme changes the conformations of the substrate that the enzyme binds to.

That is how enzymes lower the activation energy of the reaction, by changing the conformations of the substrate to a position where the reaction would be more favorable.

 

[299678]

I guess not,
Enzyme change it's own conformation to fit the substrate, but substrate is very specific, so doesn't change. Once the substrate bind to enzyme, the enzyme-substrate complex change it's substrate, called product.
Any other different ideas?

 

[JBarr29]

guess what? It doesn't , enzyme change it's own conformation to fit with substrate, but substrate doesn't change to keep their specificity

The term induced fit is applied to the enzyme itself. The enzyme alters it's tertiary structure to promote proper interactions at the active site to allow the substrate to "fit". It really alters its structure to create the best interactions in amino acid sidechains. The substrate is unchanged however, so I and II are correct, while III is incorrect.

 

[299678]

Great ! thank you

 

[UCB05]

Also be aware that receptor binding and enzyme catalysis are two different processes. If you're confused about how enzyme binding can match the answer given in the question, it's because it does not. The principle behind enzyme catalysis is that the enzyme will bind to and modify the substrate. That is the entire purpose of the enzyme, and in many cases the modification of the substrate and destruction of optimal binding sites is what kicks off the substrate to end the reaction.

In receptor signaling, the purpose of the signaling molecule is to initiate a cascade response. It cannot completely do this if the ligand is modified halfway through the process. It would be counterproductive to screw with the signaling molecule, so the ligand is not modified.

 

[sfoksn]

I am confused..

In enzyme-substrate interaction, the substrate is changed, right?

 

[akeurogh]

I am confused..

In enzyme-substrate interaction, the substrate is changed, right?

no the substrate is not changed. the enzyme changes its own conformation. if the substrate is changed the specificity will be lost.

 

[sfoksn]

i know the induced fit model of enzyme, but once the substrate binds to the enzyme, won't the substrate change (ex. starch broken into maltose by amylase)?

bio questions are hard just because its hard to understand what they are fishing for...

 

[akeurogh]

i know the induced fit model of enzyme, but once the substrate binds to the enzyme, won't the substrate change (ex. starch broken into maltose by amylase)?

bio questions are hard just because its hard to understand what they are fishing for...

in this case the reaction causes starch to be broken down. but amylase first needs to conform to starch, then the enzymatic reaction proceeds.