Question

1)Which of the following is/are example(s) of paracrine signaling?

	a.	The release of a protein into interstitial fluid that then binds to a receptor on the surface of another cell.
	b.	The release of a protein into plasma that then binds to a receptor on the surface of another cell.
	c.	The binding of a protein on the surface of cell to a receptor on the surface of another cell.
	d.	both a) and b) are correct, and c) is incorrect
	e.	a), b) and c) are all correct

2)

Select the MOST CORRECT answer.

	a.	The relative concentration of sodium ions in the sarcoplasm is higher than extracellular fluid but lower than the intercellular fluid of a motor neuron.
	b.	The relative concentration of sodium ions in the t-tubule is higher than extracellular fluid but lower than the interstitial fluid.
	c.	The relative concentration of sodium ions in the interstitial fluid is higher than the sarcoplasm and higher than the intracellular concentration of the motor neuron.
	d.	both a) and b) are correct, and c) is incorrect
	e.	a), b) and c) are all correct

Answer 1

Answer 1: d. both a) and b) are correct, and c) is incorrect

Explanation: Paracrine signaling occurs when the cell secretes the signal molecule (called a paracrine) close to the target cells and the molecules reach the target cell receptors by diffusion through the interstitial fluid.

Answer 2: c. The relative concentration of sodium ions in the interstitial fluid is higher than the sarcoplasm and higher than the intracellular concentration of the motor neuron.

Explanation: Sarcoplasm is the cytoplasm of muscle cells and is similar in properties to neurons.