Question

Why is cAMP-mediated signal amplification not required in steroid hormone signaling? Describe how steroid signaling is amplified instead.

a) Steroid hormones directly bind to cell surface receptors, initiating amplification.
b) Steroid hormones rapidly diffuse into cells, leading to signal amplification.
c) Steroid hormones activate protein kinases, avoiding the need for amplification.
d) Steroid hormones enter the nucleus and activate gene transcription, achieving amplification

Answer 1

Steroid hormones do not require cAMP for signal transduction because they can enter cells and directly affect gene transcription. This intracellular interaction amplifies the signal by altering protein synthesis levels.

Step-by-step explanation:

cAMP-mediated signal amplification is not required in steroid hormone signaling because these hormones operate through a different mechanism. Unlike water-soluble hormones that require a second messenger like cAMP for signal transduction, steroid hormones are lipid-soluble and can easily diffuse across cell membranes to enter cells. Once inside, they bind to specific intracellular receptors either in the cytoplasm or directly in the nucleus.

This hormone-receptor complex then migrates to the DNA and acts as a transcription factor, regulating the expression of specific genes. The resultant increase in mRNA leads to the production of proteins, which can have various effects in the cell. This process itself acts as a form of signal amplification, as a single steroid hormone can affect the expression level of multiple copies of a particular gene, leading to the synthesis of many protein molecules and thereby amplifying the signal without needing intermediates like cAMP.

In summary, steroid hormones achieve amplification through their direct effect on gene transcription, which increases protein synthesis and needs no intermediate steps like those involving cAMP in other hormone signaling pathways.

Answer 2

The cAMP-mediated signal amplification not required in steroid hormone signalingd) Steroid hormones enter the nucleus and activate gene transcription, achieving amplification.

Step-by-step explanation:

Steroid hormone signaling operates differently from other signaling pathways like those mediated by cAMP.

In the case of steroid hormones, the amplification occurs through a direct impact on gene transcription.

Unlike cAMP-mediated signaling, where secondary messengers are involved in signal amplification, steroid hormones, such as estrogen or testosterone, enter the target cells and move into the nucleus.

Within the nucleus, these steroid hormones bind to specific nuclear receptors, forming hormone-receptor complexes.

These complexes then bind to DNA and modulate gene transcription. This process leads to the synthesis of mRNA, which, in turn, results in the production of new proteins.

The involvement of gene transcription in the response to steroid hormones provides a robust and direct mechanism for signal amplification without the need for intermediaries like cAMP.

This direct influence on gene expression allows steroid hormones to exert profound and prolonged effects on cellular function.

It enables a single hormone-receptor interaction to trigger the synthesis of multiple proteins, contributing to the overall amplification of the signal.

In summary, the correct answer is d. Steroid hormones enter the nucleus and activate gene transcription, achieving amplification.