Chapter 9, Problem 1TYK

In signal transduction, which of the following is not a target protein?

a. proteins that regulate gene activity

b. hormones that activate the receptor

c. enzymes of pathways

d. transport proteins

e. enzymes of cell reactions

Summary Introduction

Introduction:

Signal transduction involves changing of signal into such a form that can induce the cellular response. In this, signal in form of impulse or hormone is received by the plasma membrane receptors, which then initiate cascade of reactions capable of causing the activation of target protein that brings about the desired response. These target proteins can be transporters, enzymes, or regulatory proteins.

Answer to Problem 1TYK

Correct answer:

Hormones that activate the receptor.

Explanation of Solution

Justification/explanation for the correct answer:

Option (b) states that the hormones that activate the receptor are not a target protein. This is so because hormones are the first messenger, which is actually the signal received by the plasma membrane receptors and is not the target proteins. Hence, the option (b) is correct.

The explanation for the incorrect answers:

Option (a) states that the proteins that regulate gene activity are not target proteins. These act as target proteins when signal is meant to synthesize protein from a particular gene. So, it is an incorrect option.

Option (c) states that the enzymes of pathways are not target proteins. These enzymes are targeted by signal when it tends to regulate a metabolic pathway. So, it is an incorrect option.

Option (d) states that transport proteins are not target proteins. Transport proteins are targeted in the cases when the ions or molecules need to be transported via plasma membrane. So, it is an incorrect option.

Option (e) states that enzymes of cell reactions are not target proteins. Some of the enzymes of metabolic pathways are involved in the regulation of these pathways. These are controlled by certain hormones so, act as target proteins. So, it is an incorrect option.

Hence, options (a), (c), (d), and (e) are incorrect.

Conclusion

Therefore, it can be concluded that the target proteins are the molecules, which bring about a change in cellular reactions. These molecules include transport proteins, regulatory proteins, and enzymes.