Question

a student places a fresh cucumber slice in a bowl of salty water. after 30 minutes, the cucumber becomes limp and shriveled. what caused this change?
salt entered the cucumber cells, causing them to expand.
water moved out of the cucumber cells because the salt solution was hypertonic.
water moved into the cucumber cells, causing them to swell.
the cucumber absorbed salt and water equally, keeping its shape.
the plasma membrane is mainly made up of which three types of molecules?

Explanation:

1. For the cucumber - water moves out of cells in a hypertonic solution (salty water) due to osmosis, making the cucumber limp and shriveled. Salt doesn't enter cells to cause expansion as plant cell walls limit expansion. Water moving in would cause swelling which is not the case here, and equal absorption of salt and water wouldn't lead to such a change.
2. The plasma membrane is mainly made of phospholipids, proteins, and carbohydrates. Phospholipids form the bilayer, proteins have various functions like transport and signaling, and carbohydrates are often attached to proteins or lipids for cell - cell recognition.

Answer:

1. Water moved out of the cucumber cells because the salt solution was hypertonic.
2. Phospholipids, proteins, carbohydrates.