Question

chapter 8: an introduction to metabolism
initial substrate (threonine)
threonine in active site
enzyme 1 (threonine deaminase)
intermediate a
enzyme 2
intermediate b
enzyme 3
intermediate c
enzyme 4
intermediate d
enzyme 5
end product (isoleucine)
active site available
isoleucine used up by cell
feedback inhibition
active site of enzyme 1 is no longer able to catalyze the conversion of threonine to intermediate a; pathway is switched off.
isoleucine binds to allosteric site.
a. what is the substrate molecule that initiates this metabolic pathway?
b. what is the inhibitor molecule
c. what type of inhibitor is it?
d. when does it have the most significant regulatory effect?
e. what is this type of metabolic control called?

Explanation:

Step1: Identify substrate

The initial substrate is labeled in the diagram as threonine.

Step2: Identify inhibitor

The end - product isoleucine binds to the allosteric site of enzyme 1, acting as an inhibitor.

Step3: Determine inhibitor type

Since it binds to an allosteric site, it is an allosteric inhibitor.

Step4: Determine when regulatory effect is significant

When the concentration of isoleucine is high (as it builds up), it has the most significant regulatory effect.

Step5: Name metabolic control

This is called feedback inhibition as the end - product inhibits the initial enzyme in the pathway.

Answer:

a. Threonine
b. Isoleucine
c. Allosteric inhibitor
d. When the concentration of isoleucine is high
e. Feedback inhibition