Quantcast

EK Biology In-Class Exam Lecture 1

BeMo Free Repeat™ On Us + MCAT 520 Challenge™
This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.

futuredoctor10

Full Member
10+ Year Member
Joined
Jan 25, 2007
Messages
1,625
Reaction score
21
Question.

Passage: "Arsenate, a derivative of arsenic, is a deadly poison that acts as a substrate for glyceraldehyde 3-phosphate dehydrogenase."

Question:
The action of arsenate on glyceraldehyde 3-phosphate dehydrogenase is best described as:
A. competitive inhibition
B. noncompetitive inhibition
C. allosteric inhibition
D. negative feedback

Based on the passage alone, you cannot distinguish if the inhibition is competitive or noncompetitive, correct?


I think the way to answer this question is to look at the answer choices. D cannot be correct. According to EK, "You will not be asked to distinguish allosteric inhibition from noncompetitive inhibition on the MCAT." First off is this statement true?



If so, then B and C are the same choice, and by process of elimination A must be correct.

Does "substrate" imply a substrate at the active site and therefore competitive inhibition? Or do you call molecules that bind at places other than the active site (noncompetitive inhibitors) 'substrates' as well?
 

futuredoctor10

Full Member
10+ Year Member
Joined
Jan 25, 2007
Messages
1,625
Reaction score
21
Thanks! So substrates bind the active site.
Molecules that bind an allosteric site are called what?

Also allosteric inhibition = noncompetitive inhibition for MCAT purposes right?
 

G1SG2

Full Member
10+ Year Member
5+ Year Member
Joined
May 2, 2008
Messages
1,454
Reaction score
2
Thanks! So substrates bind the active site.
Molecules that bind an allosteric site are called what?

Well, the term "substrate" can be used rather loosely...it can also refer to noncompetitive inhibition but I think your process of elimination worked well to answer the question. For allosteric regulation, the regulatory molecule is usually referred to as an activator (enhances the protein's activity) or inhibitor (represses its activity).
 
Top