Name _________________________________ Date ____________________ Period _________
Cell Membrane & Molecular Movement Worksheet
1. DIFFUSION is the movement of particles from areas of higher concentration to areas of lower
concentration. It is a natural, random process. This means that it does not require extra energy input. Use
arrows to show the flow of particles due to diffusion and explain why the molecules would move in that
direction.
2. Give an everyday example of diffusion in air and in water.
AIR:
WATER:
3. OSMOSIS is the diffusion of water across a membrane. The membrane acts like a filter that lets only the water
through. Water always goes from the area of higher water concentration to the area of lower water concentration.
(Use the bolded letters to label the diagram.)
Label the diagrams
membrane (M)
area of higher water concentration (HC)
area of lower water concentration (LC)
direction of osmotic flow (arrow)
equilibrium state (Eq)
4. Use arrows to indicate the direction of diffusion in each case:
A)
B)
5. For each of the “cells” below, calculate the amount of water both inside and outside the cell, then use an arrow
to indicate the net movement of WATER into or out of the cell. (Hint: The solute concentration is given. You need
to find the movement of the solvent.)
30% sugar
45% sugar
22% sugar
_______H2O
_______H2O
______H2O
20% sugar
________ H2O
8% sugar
_______ H2O
22% sugar
_______ H2O
6. What does diffusion and osmosis have to do with the cell membrane? Well, the cell membrane is selectively
permeable. That means that water and oxygen can move freely across the cell's membrane by diffusion but larger
molecules need help.
Consider these situations:
Carrot: 90% H2O
Celery: 95% H2O
Raisin: 15% H2O
Water: 99% H2O
Salt water: 75% H2O
Use your understanding of osmosis and diffusion to explain what will happen to the carrot,
celery and raisin in each of the solutions.
SALT WATER
FRESH WATER
7. The cell membrane is made of a ___________________ ______________________.
8. The cell membrane is ______________________ permeable. This means that ________________
________________________________________________________________________________.
9. Diffusion always causes particles to move from a region of _______________ concentration to a region of
______________ concentration.
10. What are some factors that can affect the rate of diffusion?