![Q.39 Which of the following strategies are used by cells for metabolic regulation! [P] Phosphorylation- dephosphorylation [Q] Allostery [R| Feedback inhibition (A) P and Q only (B) P and R only (C) Q and R only (D) P, Q and R](https://www.letstalkacademy.com/wp-content/uploads/2026/01/slide_39-10.png)
Q.39 Which of the following strategies are used by
cells for metabolic regulation!
[P] Phosphorylation- dephosphorylation
[Q] Allostery
[R| Feedback inhibition
(A) P and Q only
(B) P and R only
(C) Q and R only
(D) P, Q and R
Cells use multiple strategies for metabolic regulation, including all three options listed: phosphorylation-dephosphorylation (P), allostery (Q), and feedback inhibition (R). The correct answer is (D) P, Q, and R.
Option Analysis
P: Phosphorylation-Dephosphorylation
This covalent modification adds or removes phosphate groups on enzymes via kinases and phosphatases, altering activity, often in response to signals like hormones. For example, glycogen synthase is inactivated by phosphorylation.
Q: Allostery
Allosteric regulation involves effector molecules binding at sites distant from the active site, inducing conformational changes that activate or inhibit enzymes. ATP inhibits phosphofructokinase in glycolysis through this mechanism.
R: Feedback Inhibition
This occurs when a pathway’s end product inhibits an early enzyme, preventing overproduction. Threonine deaminase in isoleucine synthesis is inhibited by isoleucine.
Cells metabolic regulation strategies ensure efficient energy use and homeostasis by fine-tuning enzyme activities. These mechanisms—phosphorylation-dephosphorylation, allostery, and feedback inhibition—prevent wasteful overproduction and respond dynamically to cellular needs.
Phosphorylation-Dephosphorylation in Action
Kinases add phosphate groups to serine, threonine, or tyrosine residues, often deactivating enzymes, while phosphatases reverse this. In signal transduction, cAMP-dependent protein kinase (PKA) phosphorylates enzymes during fight-or-flight responses.
Allostery Mechanism
Allosteric effectors bind non-active sites, shifting enzyme conformation between tense (T, low activity) and relaxed (R, high activity) states. In glycolysis, fructose-2,6-bisphosphate activates phosphofructokinase allosterically.
Feedback Inhibition Role
End-products bind early pathway enzymes, providing rapid negative control. Aspartate transcarbamoylase (ATCase) in pyrimidine synthesis is inhibited by CTP.
| Strategy | Example Enzyme | Effector/Trigger | Pathway |
|---|---|---|---|
| P | Glycogen synthase | Phosphorylation by GSK3 | Glycogen synthesis |
| Q | Phosphofructokinase | ATP (inhibitor) | Glycolysis |
| R | Threonine deaminase | Isoleucine | Amino acid biosynthesis |
These cells metabolic regulation strategies are essential for competitive exams like IIT JAM Biotechnology, emphasizing their integration in metabolic control.
