Estrogen and testosterone are steroid hormones, and most likely bind to

Options

A. membrane ion channel
B. enzyme-linked membrane receptors
C. G-protein coupled membrane recepitors
D. cytoplasmic receptors.

Answer

### Step-by-Step Solution:

1. **Identify the Hormones**: Recognize that estrogen and testosterone are steroid hormones. This is important because their chemical nature influences how they interact with cells.

2. **Understand the Nature of Steroid Hormones**: Acknowledge that steroid hormones are hydrophobic (lipophilic) molecules. This characteristic allows them to diffuse freely across cell membranes, which are primarily composed of lipid bilayers.

3. **Mechanism of Action**: Once inside the cell, steroid hormones do not bind to receptors on the cell surface like many other hormones. Instead, they enter the cytoplasm of the target cell.

4. **Binding to Receptors**: In the cytoplasm, steroid hormones bind to specific receptor proteins. These receptors are often referred to as cytoplasmic receptors.

5. **Formation of Hormone-Receptor Complex**: After binding, the hormone-receptor complex translocates into the nucleus of the cell.

6. **Activation of Gene Expression**: Inside the nucleus, the hormone-receptor complex binds to specific DNA sequences, leading to the activation or repression of target genes, which ultimately results in specific physiological responses.

7. **Conclusion**: Therefore, the correct answer to the question is that estrogen and testosterone most likely bind to cytoplasmic receptors.

### Final Answer:
Estrogen and testosterone are steroid hormones that most likely bind to cytoplasmic receptors.

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