Question

a bacteria was added to a solution containing penicillin. after several days, the bacterial cells appeared healthy and unaffected by the penicillin. what can be inferred about the tonicity of the solution in which the bacteria were placed?
the concentration of penicillin in the solution was higher than the solute concentration.
the solution was hypertonic and therefore unaffected by the penicillin.
the solution was isotonic and therefore penicillin did not increase the flow of water into or out of the cell.
the solution was hypotonic and therefore unaffected by the penicillin

Explanation:

Penicillin works by interfering with cell wall synthesis, but its effectiveness can be influenced by osmotic balance. In an isotonic solution, the solute concentration inside and outside the cell is equal, so there is no net movement of water. This stable osmotic environment means penicillin does not disrupt water flow (which could otherwise affect cell integrity), allowing the bacteria to remain healthy as described. The other options are incorrect: hypertonic/hypotonic solutions cause water loss/gain (which would harm cells), and the first option confuses penicillin concentration with overall solute concentration.

Answer:

The solution was isotonic and therefore penicillin did not increase the flow of water into or out of the cell.