Feedback Inhibition

[shefv]

Do feedback inhibitions always work by affecting the activity of the enzymes involved in a pathway (where negative inhibition decrease activity of the enzyme and positive inhibition increases activity of the enzymes)?

Are the terms "negative feedback loop" and "negative inhibition" referring to the same concept?

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[ElectricNoogie]

Generally feedback inhibition is a type of inhibition where a downstream or end product will inhibit an upstream enzyme.

A negative feedback loop is similar and can occur in neuro or endocrine systems. In endocrine a negative feedback loop is designed to return the system to the status quo. That means if a level of something gets too high or too low, a negative feedback loop will turn on or off the appropriate hormone or action to return the system to the status quo. Almost all homeostatic control mechanisms are negative feedback mechanisms.

For example in the control of blood sugar when blood sugar rises, receptors in the body sense the increase. In response, the pancreas will secrete insulin into the blood to lowering blood sugar levels. Once blood sugar levels reach homeostasis, another signal is sent and the pancreas stops releasing insulin.

Both methods refer to modulating upstream actions to change a downstream effect.

Hope this helps!

 

[shefv]

Thanks!

For negative inhibition, does the product always bind to the allosteric site on the enzyme to exert a negative control? or can it also bind to the active site?

For positive inhibition, is it the same thing - product binding to the allosteric site but this time increasing the activity of the enzyme?

I am trying to understand the exact mechanism by which this process works.

 

[RH8448]

Understand the general concept. Almost everything in biology is based mostly upon negative feedback and some positive feedback. This means many mechanisms exist. Having said that, generally, this can occur by allosteric regulation and "active site binding" as you said. For "active site binding" think about the lac operon. For allosteric, think about metabolism (TCA, ETC, Glycolysis). The types of inhibition (mixed, competitive, noncompet., uncompet.) is also very closely related to this concept of allosteric regulation and competitive inhibition.

If a mechanism is found on the exam, it would require you to use organic chemistry/biochemistry knowledge to investigate how to mechanism actually works.