In basic cell biology and solutions, a solution that is hypotonic to a cell has which relative amount of water molecules compared to the inside of the cell?

Introduction / Context:
The idea of hypotonic, isotonic, and hypertonic solutions is important in both biology and chemistry. These terms describe the relative concentrations of solutes and water inside and outside cells. This question asks what is true of a solution that is hypotonic to a cell, focusing on where water molecules are more abundant.

Given Data / Assumptions:
- A hypotonic solution has a lower solute concentration compared to the cell interior.
- Water naturally moves from regions of higher water concentration to regions of lower water concentration through osmosis.
- We are comparing the amount of water molecules outside and inside the cell.

Concept / Approach:
If a solution is hypotonic relative to the cytoplasm, it means the solution has fewer solute particles and therefore more water per unit volume than the inside of the cell. Because water moves down its concentration gradient, it tends to move into the cell. The key is recognising that low solute concentration outside means high water concentration outside. Therefore, in a hypotonic environment, more water surrounds the cell than is present inside, and the cell may swell as water enters.

Step-by-Step Solution:
Step 1: Recall that hypotonic means lower solute concentration outside the cell than inside. Step 2: Understand that if solute concentration is low outside, water concentration is high outside, because solution composition is shared between solute and solvent. Step 3: Compare water abundance: outside has more water molecules, inside has relatively fewer because of higher solute content. Step 4: Water will move from the region with more water to the region with less water, so it flows into the cell by osmosis. Step 5: Conclude that a solution hypotonic to a cell has more water molecules surrounding the cell than inside the cell.

Verification / Alternative check:
In biology textbooks, placing animal cells in hypotonic solutions often causes them to swell or even burst because water enters the cell. Plant cells become turgid under these conditions because their cell walls resist bursting. Both effects rely on the outside having higher water concentration and lower solute concentration, exactly matching the description of a hypotonic solution. This behavioural evidence supports the logical definition and confirms the correct option.

Why Other Options Are Wrong:
- More water molecules inside the cell than outside: This describes a hypertonic external solution, where water tends to move out of the cell, not a hypotonic one.
- Equal numbers of water molecules inside and outside: This corresponds to an isotonic situation in which there is no net movement of water.
- No water molecules inside the cell: This is biologically impossible because cells are largely water based structures.
- No water molecules outside the cell: This is also unrealistic because solutions outside cells are aqueous in most biological contexts.

Common Pitfalls:
Students often confuse solute concentration with water concentration and reverse the direction of water movement. Another mistake is mixing up hypotonic and hypertonic definitions. A reliable memory aid is that hypo suggests less solute outside, which implies more water outside, causing water to move into the cell. Keeping this relation clear prevents confusion on related questions.

Final Answer:
A solution that is hypotonic to a cell has More water molecules surrounding the cell than inside the cell.