The Number of Radioactive Nuclei in a Particular Sample Decreases $9 / 8$

question 42

Multiple Choice

The number of radioactive nuclei in a particular sample decreases to one-eighth of its original number in 9 days. What is the half-life of these nuclei?

• A) 3 days
• B) 10 days
• C) 8 days
• D) 2 days
• E) \(9 / 8\) days

---

Definitions:

Thyroid Hormones

Hormones, including thyroxin (T4) and triiodothyronine (T3), secreted by the thyroid gland; stimulate rate of metabolism.

Surface Receptors

Proteins located on the cell membrane that bind to specific molecules in the cell's external environment, initiating a cellular response.

Second Messengers

Intracellular signaling molecules released by a cell in response to exposure to extracellular signaling molecules, amplifying the signal within the target cell.

Paracrine Regulation

Paracrine regulation involves the signaling of cells to nearby cells by releasing chemical messengers, influencing the behavior of those nearby cells without needing to enter the bloodstream.