Diffusion & Osmosis Practice
KEY
PURPOSE
Understand the processes of diffusion and osmosis in cells.
1. Look at these pictures of a cell surrounded by sugar molecules. The small dots are sugar molecules.
Circle the picture that correctly shows where the sugar molecules should appear after diffusion has taken
place.
Before
After
2. What is diffusion? The movement of molecules from areas of high conc. to areas of low conc. _______________
3. How do molecules get through the cell membrane? By cellular transport. Some diffuse through, some need protein
channels. ____________________________________________________________________________________
____________________________________________________________________________________________
4. What is osmosis? The diffusion of water across a semi-permeable membrane ____________________________
5. Which way would the water move in the following?
a. cucumber slice in salt water Out of the cucumber, into the salt water __________________________________
b. salt poured on a snail Out of the snail, into the salt ________________________________________________
c.
vegetables sprinkled with water Into the vegetables, out of the water __________________________________
6. Look at these diagrams of cells. They show osmosis of water molecules taking place. Shade in one arrow in each
diagram that correctly shows the overall direction in which water molecules will move.
= water
A
B
C
D
7. Circle the letter of the sentence that best explains what osmosis is.
A. Osmosis is the movement of water into or out of a cell from where it is in large amounts to small amounts.
B. Osmosis is the movement of water into or out of a cell from where it is in small amounts to large amounts.
C. Osmosis is the movement of water into or out of a cell if diffusion is present.
8. Water molecules will move into or out of a cell until the number of molecules in the cell is equal to the number on
the outside. How many water molecules will move in the direction of the shaded arrow in each of the following?
Cell A _8
Cell B _7_
Cell C _1_
Cell D _1__