When a bacterial cell is placed in a solution containing 5% NaCl, the solution is hypertonic to the cell, so water moves out of the cell by osmosis, causing it to shrink (plasmolysis) and potentially be inhibited or killed.

Quick Scoop: What Happens in 5% NaCl?

A 5% NaCl solution has a higher solute concentration than the inside of most bacterial cells, so it pulls water out of the cell.

  • The solution is hypertonic to the bacterial cytoplasm.
  • Water leaves the cell, moving from higher water concentration (inside) to lower (outside).
  • The cytoplasmic membrane pulls away from the cell wall (plasmolysis), and the cell shrivels.
  • Growth is inhibited; prolonged exposure can lead to cell death.

If this came from a multiple-choice quiz, the best statement is typically:

“Water will leave the bacterial cell, causing it to shrink (plasmolyze) in a hypertonic 5% NaCl solution.”

Why 5% NaCl Matters for Bacteria

Many microbes grow best at low salt levels; 5% NaCl is already stressful for non–halophilic bacteria.

  • Elevated NaCl creates osmotic stress that slows growth and stresses cellular functions.
  • At around 5% NaCl, many bacteria show injury or structural damage, especially more sensitive species like E. coli.
  • Food preservation often uses salt on this principle: remove water from microbes so they cannot grow.

A simple way to picture it: the salty solution “dehydrates” the bacterial cell from the outside.

Osmosis and Tonicity (Mini Refresher)

  • Hypotonic : Solution has less solute than the cell; water moves in; wall-bearing bacteria usually swell slightly but do not burst easily.
  • Isotonic : Equal solute inside and out; no net water movement.
  • Hypertonic (like 5% NaCl here): More solute outside; water moves out; cell shrinks (plasmolysis).

Bacterial cell walls give some mechanical protection, but they cannot prevent water loss in a hypertonic environment.

Sample Answer for Exams / Quizzes

If you need a concise exam-style line:

When a bacterial cell is placed in a 5% NaCl solution, the hypertonic environment causes water to leave the cell, leading to plasmolysis and possible growth inhibition or death.

Meta description (SEO-style):
Learn which statement best describes what happens when a bacterial cell is placed in a solution containing 5% NaCl: why this hypertonic environment draws water out, causes plasmolysis, and inhibits growth, as commonly tested in microbiology quizzes.

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