Download Chapter 1, Lesson 4 - Mahtomedi Middle School

The Cell in Its Environment – pg. 28
How Do Materials Move Into and Out of Cells?
Lab Activity (with your pod):

1. Fill beaker ½ way with cold water. Place the beaker

2. Add one drop of food coloring to the water.

3. Observe for a few minutes and write down changes

4. Bring materials back & wait to discuss with class
on the desk and allow it to sit until there is no
movement in the water.
you notice on p. 28 in the margin.
Words you may have used to describe:
• Starts as a glob of color in the middle
• Color spreads out slowly
• After a while, the color became more equal throughout
Oxygen
 Water
 Food Particles (salts & sugars)
 Carbon dioxide
 Waste materials

**Highlight/underline those!



Structure: Double layer of lipid molecules
lined up side by side
Selectively permeable: some substance can
cross the membrane while others cannot
Substances can move in & out of a cell by
passive transport or
active transport
Check out 3 of the 5 molecules that all
living things have!!!
• Carbohydrates
• Lipids
• Proteins
In what way is the cell membrane like
a gatekeeper?
Answer: It is in charge of
controlling who comes in
or out of the cell!

Passive Transport: the movement
of dissolved materials across a cell
membrane without using the cell’s
energy
 Fun example: riding a bike down a hill
 Molecules
 They
are always moving!
bump into each other
 Over
time, as molecules continue colliding
and moving apart, they become less
concentrated (crowded)
 Eventually,
the molecules spread evenly
throughout the space
Ouch! That
kinda hurt!

The process where molecules move from an
area of higher concentration to an area of
lower concentration.
Figure 2…take a look at this
Diffusion
A drop of food coloring in a plate of gelatin gradually
spreads as molecules of the dye diffuse. How would the
third plate look if diffusion continues?
Figure 2…take a look at this
Diffusion
A drop of food coloring in a plate of gelatin gradually
spreads as molecules of the dye diffuse. How would the
third plate look if diffusion continues?
You should
have a
picture of
dye spread
in a wider
circle

Link to eyeball science:
◦ http://kitchenpantryscientist.com/edible-eyeballs-a-diffusionexperiment-for-halloween/
Think about this…
Here is a little water critter – a Paramecium (found
in pond water)
nucleus
Contractile
vacuole
Think about this…
All living things need oxygen – a Paramecium
doesn’t have lungs to breathe in oxygen so it gets it
from the water.
Think about this…
What is water made of?
Hydrogen and Oxygen!!!
Think about this…
So, how does the oxygen get INTO the
Paramecium’s body?
DIFFUSION
Think about this…
Diffusion is one form of passive
transport because the
concentration of oxygen is higher
outside the paramecium than it is
inside of it. So…oxygen moves
easily into the cell
Make a quick sketch of this in the margin on
page 30.
 The
diffusion of water molecules
across a selectively permeable membrane
◦ Cells cannot function properly without water
◦ Form of passive transport

Read 2nd paragraph & Figure 3, Effects of
Osmosis…let’s do that


The top picture
shows a healthy
plant cell – water
moving in and out
through the cell
membrane.
The 2nd picture
shows how the cell
membrane has
pulled away from
the cell because too
much water is lost.

Can this happen to us too? YEP – think
about being stranded on a desert island –
no fresh water.

https://www.youtube.com/watch?v=z7Rv_7k
WfBc

Leech or Slug murder
◦ Salt on a leech or slug
will kill it because their
skin has no protective
barrier to it. Water
leaves their cells to
balance out the salt.

Diffusion and Osmosis
◦ Diffusion – molecules going from crowded to less crowded
places
 Energy not needed
 Does not involve water
◦ Osmosis – Diffusion of water
 Water molecules going from crowded to less crowded places

What does passive transport mean again?
◦ Movement of molecules across a membrane without
needing energy

Movement of materials across a cell membrane
using cellular energy
◦ Molecules move from areas of lower concentration to
higher concentration
◦ Proteins move these molecules across the cell
membrane – (see figure 4)
◦ Substances that do this include calcium, potassium,
and sodium
Crossing the Cell Membrane - figure 4 (pg. 32)
Crossing the
Cell Membrane
Molecules move into
and out of
a cell by means of
passive or active
transport. Complete
the boxes, and
describe where the
concentration of each
substance is high or
low.
Crossing the Cell Membrane - figure 4 (pg. 32)
Passive
Crossing the
Cell Membrane
Molecules move into
and out of
a cell by means of
passive or active
transport. Complete
the boxes, and
describe where the
concentration of each
substance is high or
low.
Osmosis
Diffusion
Active
 Use
diffusion to tell what happens
when you drop a sugar cube into
water.
 Sugar dissolves; molecules collide
moving from high concentration to
low concentration
 Draw
an arrow to show the overall
direction water will travel as a result
of osmosis. (The yellow line is the cell membrane)
 Active
transport depends on
to move molecules across the cell
membrane.
Proteins
 How
does active transport differ from
passive transport?
 Active transport uses cell energy in
moving materials into or out of cells;
passive transport does not.
 Now
I know that the key function of the
cell membrane is to…
 Regulate the materials that move
into and out of cells