Final answer:
A low concentration of both K ions and proteins would be found in the interstitial fluid, a part of the extracellular fluid. This is because the extracellular fluid has a higher concentration of other ions like Na and Cl, and a lower concentration of K ions and proteins compared to the intracellular fluid.
Step-by-step explanation:
The student is asking which compartment of the body fluid contains a low concentration of both K ions and proteins. In this context, the term compartment refers to the different fluid environments of the body, namely the intracellular fluid (ICF), extracellular fluid (ECF), plasma, and interstitial fluid (IF).
The intracellular fluid, which makes up about 50% of the total body weight, is known to have high concentrations of potassium (K) and proteins. On the other hand, the extracellular fluid, including plasma and interstitial fluid, which accounts for approximately 20% of body weight, has a higher concentration of sodium (Na) and chloride (Cl) ions but a lower concentration of proteins and K ions.
When comparing the different fluids, we find that the extracellular fluid, particularly the interstitial fluid, has a lower concentration of proteins compared to plasma, and also has relatively low concentrations of K ions. Therefore, the correct answer to the student's question is that a low concentration of both K ions and proteins would be found in the interstitial fluid, which is a part of the extracellular fluid.