Download Moving Materials in and out of cells

TEACHER MASTER
Cells and Systems - Science 8
Moving Materials in and out of Cells
Learning Outcomes Addressed
B2. relate the main features and properties of cells to their function
- relate the concepts of osmosis and diffusion to transport of materials across cell membranes
 Recommended time required for this activity: 15 minutes
 Special Notes: This is a general introduction of diffusion and
osmosis. The Nelson science probe has an excellent description
of these processes in more detail.
 Suggested corresponding review questions from Nelson Science
Probe 8 (if applicable):
o 1.7 #1-8 pg 24
o 1.8 #1-6 pg 28
 Suggested corresponding Inquiry Investigations from Nelson
Science Probe:
o 1.9 Observing Diffusion and Osmosis pg 29
o 1.10 How does the Concentration of a Solution affect
Osmosis pg 32
Notes and Activities – Science 8
TEACHER MASTER
Cells and Systems - Science 8
Moving Materials in and out of Cells
Cells and all of their organelles need NUTRIENTS and
WATER to function and make energy SO there must be
a way of getting these into the cell. Cells also must be
able to get rid of WASTES.
The outer layer of plant cells is the CELL WALL and
the outer layer of animal cells is the CELL
MEMBRANE. All materials entering and leaving the cell
must pass through this. The cell wall just has openings
in it which most materials can pass through.
The CELL MEMBRANE is what actually acts as the
“GATEKEEPER” of the cell and controls what enters
and leaves the cell.
CELL MEMBRANES
- are made up of proteins and fatty acids
- are selectively permeable (some materials are
allowed to move through and some are not)
example: the small molecules can pass through the membrane but the large
molecules cannot and thus stay on one side.
Notes and Activities – Science 8
TEACHER MASTER
Cells and Systems - Science 8
How do these molecules move?
1. DIFFUSION
The movement of materials from an area of high
concentration (lots of molecules)
to an area of low concentration (less molecules)
When a cell needs certain nutrients there is less of the
material inside the cell than there is outside the cell.
Therefore, the nutrients will move inside the cell
automatically because of the concentration difference.
A real life example of diffusion:
- spraying air freshener in a corner of a room…
2. OSMOSIS
Cells are made up of 99.9% WATER and this is very
important in the functioning of cells.
Osmosis is just a fancy word for the DIFFUSION OF
WATER. It is the process by which cells take in water
or lose water and it helps them maintain proper
balance.
Notes and Activities – Science 8
TEACHER MASTER
Cells and Systems - Science 8
WHAT HAPPENS WHEN A MOLECULE IS TOO BIG
TO FIT THROUGH THE OPENINGS IN THE CELL
MEMBRANE BUT NEEDS TO GET INTO THE CELL?
They would need to use a method called ACTIVE
TRANSPORT. In this method special carrier proteins in
the cell membrane shuttle these molecules across.
Many vitamins and minerals must use this method of
entering the cell as they are very large molecules.
Notes and Activities – Science 8