Question

If a solution surrounding a cell is hypertonic relative to the inside of the cell, how will water move? a. It will move into the cell via osmosis. b. It will move out of the cell via osmosis. e. It will not move, because equilibrium exists. d. It will evaporate from the cell surface more rapidly.

Short answer

In a situation where a cell is surrounded by a hypertonic solution (higher solute concentration outside the cell), water will move out of the cell via osmosis to reach equilibrium. Therefore, the correct answer is (b).

Step-by-step solution

1. Understanding Osmosis

Osmosis is the movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration. This movement occurs until an equilibrium is reached between the two regions.

2. Defining Hypertonic, Hypotonic, and Isotonic solutions

A hypertonic solution is a solution with a higher solute concentration compared to another solution (in this case, the cell). A hypotonic solution has a lower solute concentration compared to another solution (the cell). An isotonic solution has the same solute concentration as another solution (the cell).

3. Analyzing the given exercise

The exercise states that the solution surrounding the cell is hypertonic relative to the inside of the cell. This means that the solute concentration outside the cell is higher than the concentration inside the cell.

4. Comparing the given options with the understanding of osmosis and hypertonic solution

Given the concept of osmosis, we can now analyze each of the given options. a. Water moving into the cell via osmosis would mean the solution outside is hypotonic, which is not the case in this exercise. b. Water moving out of the cell via osmosis aligns with the fact that the external solution is hypertonic. c. Equilibrium not existing is incorrect, as water will move via osmosis until an equilibrium is reached. d. Evaporation doesn't relate to osmosis or the movement of water across the cell membrane.

5. Selecting the correct answer

Based on our analysis, the correct answer is (b). Water will move out of the cell via osmosis because the solution surrounding the cell is hypertonic relative to the inside of the cell.

Key concepts

Hypertonic Solution

When we talk about a hypertonic solution, we are referring to a solution that has a higher concentration of solutes compared to another solution. In the context of cells, a hypertonic solution has more solute particles outside the cell than inside. This creates a situation where water will naturally move out of the cell in an attempt to balance the concentration levels.

• This movement occurs because the cell wants to equalize the differences in concentration between the inside and outside of the cell.
• Water moves out to dilute the higher concentration of solutes outside the cell.

Understanding what makes a solution hypertonic is crucial when discussing osmosis. It explains why cells in hypertonic solutions can shrink or become dehydrated as they lose water.

Selectively Permeable Membrane

The cell membrane is an incredible structure known as a selectively permeable membrane. This just means that it controls what enters and exits the cell. It lets certain molecules pass through while blocking others.

• Water molecules are small and can pass through easily.
• However, larger molecules like sugars and proteins often cannot pass through without help.

The selective nature of the membrane is important in osmosis because it allows water to move across the membrane to where it is needed. This also helps maintain the internal environment of the cell, keeping it stable despite changes outside.

Solute Concentration

Solute concentration refers to the amount of solute, like salt or sugar, dissolved in a solution. It is crucial in determining the direction of osmosis.

• If the outside solution has a higher concentration of solutes, it is labeled hypertonic.
• If it is lower, the solution is hypotonic.
• An equal concentration inside and outside is termed isotonic.

The concentration gradients created by varying solute concentrations drive the movement of water in osmosis. The cell's balance of solute concentration is vital for its survival, as an uneven balance can lead to cell shrinkage or swelling.

Osmosis Movement

Osmosis is the process by which water molecules move across a selectively permeable membrane from an area of lower solute concentration to one of higher solute concentration. This movement continues until an equilibrium is reached and the concentrations are balanced on both sides of the membrane.

• It is a passive process, so it doesn’t require energy.
• Osmosis helps maintain cell turgor pressure, which is essential for plant cells to remain firm.

In the exercise scenario, the understanding of osmosis movement explains why water leaves the cell when placed in a hypertonic solution. Osmosis continuously adjusts until there is a balance, crucial for keeping cells functioning properly.