The mechanism of action of a steroidal hormone on target cell is established through the

Options

A. formation of secondary messengers
B. activation of transcriptional apparatus.
C. attachement with cytosolic receptor protein
D. regulation of gene expression

Answer

To solve the question regarding the mechanism of action of a steroidal hormone on a target cell, we can follow these steps:

### Step 1: Understand the Nature of Steroidal Hormones
Steroidal hormones, such as cortisol, testosterone, and progesterone, are lipophilic molecules. This means they can easily pass through the lipid bilayer of cell membranes.

**Hint:** Remember that steroid hormones are derived from cholesterol and can diffuse through cell membranes.

### Step 2: Identify the Receptors for Steroidal Hormones
Once inside the cell, steroid hormones bind to specific receptors known as intracellular receptors. These receptors are located in the cytoplasm or nucleus of the target cell.

**Hint:** Think about where steroid hormones act within the cell compared to peptide hormones.

### Step 3: Formation of Hormone-Receptor Complex
The binding of the steroid hormone to its receptor forms a hormone-receptor complex. This complex then translocates to the nucleus if it is not already there.

**Hint:** Consider the importance of the hormone-receptor complex in initiating a response within the cell.

### Step 4: Regulation of Gene Expression
The hormone-receptor complex interacts with specific regions of DNA, leading to the regulation of gene expression. This can result in the transcription of mRNA and ultimately the synthesis of proteins that carry out various functions in the cell.

**Hint:** Focus on how steroid hormones influence cellular activities by altering gene expression.

### Step 5: Conclusion
Based on the understanding of the above steps, the correct answer to the question is that the mechanism of action of a steroidal hormone on a target cell is established through the regulation of gene expression.

**Final Answer:** Regulation of gene expression.