Drinking alcohol can cause dehydration, which increases blood osmolarity and makes the blood hypertonic relative to body cells. What is the most likely immediate osmotic effect on most body cells when the surrounding blood becomes hypertonic?

• A. Solutes diffuse out of cells until the extracellular fluid becomes hypotonic.
• B. Water moves out of cells by osmosis, causing cells to shrink (crenate).
• C. Water moves into cells by osmosis, causing cells to swell and potentially lyse.
• D. Active transport rapidly pumps water into cells to restore cell volume.

Answer: (B)

Verified step by step guidance

1. Understand the concept of tonicity: Tonicity refers to the relative concentration of solutes outside the cell compared to inside the cell, which affects the movement of water across the cell membrane by osmosis.
2. Identify the condition described: The blood becomes hypertonic, meaning it has a higher solute concentration (higher osmolarity) than the fluid inside the body cells.
3. Recall the principle of osmosis: Water moves from an area of lower solute concentration (inside the cells) to an area of higher solute concentration (the hypertonic blood) to balance solute concentrations on both sides of the membrane.
4. Predict the cellular response: Since water moves out of the cells into the hypertonic blood, the cells lose water and shrink, a process known as crenation.
5. Eliminate incorrect options: Solutes do not typically diffuse out to make extracellular fluid hypotonic immediately; water does not move into cells in a hypertonic environment; and active transport of water is not a mechanism cells use to restore volume quickly.