The nurse is teaching nursing students about the concept of medications’ half-life. The nurse asks students: If we administer 10 mg of medication X, which has a half-life of one day, to the patient, how much medication will remain in the patient’s body after three days?

Choice A Reason:

The statement that the medication will be completely out of the patient’s body after three days is incorrect. The half-life of a drug indicates the time it takes for the concentration of the drug in the body to reduce by half. After one half-life (one day), 50% of the drug remains. After two half-lives (two days), 25% remains. After three half-lives (three days), 12.5% remains. Therefore, some amount of the drug will still be present in the body after three days.

Choice B Reason:

To calculate the amount of medication remaining after three days, we use the half-life formula. Starting with 10 mg, after one day (one half-life), 5 mg remains. After two days (two half-lives), 2.5 mg remains. After three days (three half-lives), 1.25 mg remains. This calculation shows that 1.25 mg of the medication will still be in the patient’s body after three days.

Choice C Reason:

The choice of 5 mg is incorrect because it represents the amount of medication remaining after one half-life (one day), not three half-lives. After one day, 50% of the initial dose remains, which is 5 mg. However, the question asks for the amount remaining after three days.

Choice D Reason:

The choice of 1 mg is also incorrect. After three half-lives, the amount of medication remaining is 12.5% of the initial dose. For an initial dose of 10 mg, this would be 1.25 mg, not 1 mg. The calculation must accurately reflect the reduction by half for each half-life period.

Choice A: Move Na Inside the Cell

The primary function of the Na-K pump, also known as the sodium-potassium pump, is to move sodium (Na) ions out of the cell, not into the cell. This pump actively transports three sodium ions out of the cell for every two potassium ions it brings in. Therefore, this choice is incorrect.

Choice B: Move K Out of the Cell

The Na-K pump moves potassium (K) ions into the cell, not out of the cell. This active transport mechanism helps maintain the necessary concentration gradients of sodium and potassium across the cell membrane, which are crucial for various cellular functions, including maintaining the resting membrane potential.

Choice C: Move Na Out of the Cell

The main function of the Na-K pump is to move sodium ions out of the cell. For every cycle of the pump, three sodium ions are exported out of the cell, and two potassium ions are imported into the cell. This process is essential for maintaining the electrochemical gradient across the cell membrane, which is vital for nerve impulse transmission, muscle contraction, and overall cellular homeostasis.

Choice D: Move Na and K Inside the Cell

This choice is incorrect because the Na-K pump does not move both sodium and potassium ions inside the cell. Instead, it moves sodium ions out of the cell and potassium ions into the cell. This active transport mechanism is crucial for maintaining the proper ionic balance and membrane potential necessary for various physiological processes.