CH 5 Membranes Case Sudy

You are looking at solutes (red dots) after plenty of time has elapsed. Most of the dots are on the left. This means:

• They cannot cross membranes.

• They do not obey the law of diffusion like other chemicals.

A solution is 90% water on the left, and 80% water on the right, of a membrane that only water can cross. Assuming no other forces are operating, which direction will water move?

• Water will move from left to right.

• Water will move from right to left.

• It depends.

• It is impossible to tell.

Remember that it is important to think about the concentration of the substance that can move. Consider this question:

The solution on the left is 10% salt. On the right it is 5% salt. Salt cannot cross the membrane, but water can. Which way will water move?

• Water will move from left to right.

• Water will move from right to left.

• It depends.

• It is impossible to tell.

What do you predict will happen when you place an animal cell in a container of distilled water?

• Water will not move.

• Water will move from the cell into the beaker holding the experiment.

• Water will move into the cell for a while.

• Water will move into the cell and the cell will explode!

You place a plant cell in the same solution. The animal cell has exploded, but the plant cell never does. Why not?

• Plants are tougher than animals.

• Plants have a cell wall that pushes back against the increased cell volume.

• Plants don’t let water cross membranes.

• We have no idea.

As a dare, you make a bet with your friends that you will water all of your houseplants with saltwater for one weekend. To your dismay, all of your beloved plants die. Why do you think this happened?

• You’re an idiot

• The plant cells absorbed too much water and died

• The plants absorbed the salt molecules and were poisoned

• The plant cells lost water to the environment and plasmolyzed