Q. 19 - Biology

Question

Which protein is a positive regulator that  phosphorylates other proteins when activated?

a.    p53

b.    retinoblastoma protein (Rb)

c.    cyclin

d.    cyclin-dependent kinase (Cdk)

Step-by-Step Solution

Answer

Cyclin-dependent kinase (CDK) is a positive regulator that phosphorylates other proteins when activated. The correct option is (d).

Step 1. Introduction

The cell's progression through the numerous checkpoints is facilitated by positive regulators, which are regulatory components.

Step 2. Explanation of correct option

Positive regulators include cyclin-dependent kinases (Cdks). They're in charge of making sure the cell gets to all of the many checkpoints it has to go through. These kinases phosphorylate various proteins through the Cdk pathway. It is phosphorylation that activates the protein because it alters its structure. Cdks phosphorylate proteins that aid in the progression of the cell to another stage.

Thus, the correct option is (d).

Step 3. Explanation of Incorrect Options

p53 is one type of tumor suppressor protein, not a positive regulator that phosphorylates other proteins when activated. 

Thus, option (a) is incorrect.

As a tumor suppressor, Rb protein is crucial in regulating cell growth and tumor development. So, this is not a positive regulator that phosphorylates other proteins when activated.

Thus, option (b) is incorrect.

Cyclin is a positive regulator but does not phosphorylate other proteins when activated.

Thus, option (c) is incorrect.