What defines electrolytes in a biological context?

• A. Solids that form in plasma
• B. Substances that dissociate into ions
• C. Nonpolar molecules
• D. Charged molecules in membranes

Answer: (B)

Electrolytes are defined in a biological context as substances that dissociate into ions when dissolved in a solvent, typically water. This ionization results in the formation of charged particles, which are essential for various physiological processes. For instance, electrolytes such as sodium, potassium, chloride, and calcium ions play critical roles in maintaining fluid balance, transmitting electrical signals in muscles and nerves, and regulating pH levels in the body.

When electrolytes dissociate, they enable the conduction of electrical impulses, making them vital for cellular communication and muscle contractions. The presence of these ions in bodily fluids helps to maintain osmotic balance and acid-base homeostasis, which are crucial for overall health.

In contrast, substances that might form solids in plasma are not necessarily categorized as electrolytes since they do not freely dissociate into ions in solution. Nonpolar molecules do not interact with water in a way that would allow them to dissociate into charged particles and thus do not fulfill the role of electrolytes. Charged molecules in membranes are important in cellular function but do not encompass the broader definition of electrolytes as substances that split into ions in solution.