Transcript Chapter 3 Cell Processes

Chapter 3
Cell Processes
Ch. 3-2
Moving Cellular
Materials
Structure of the Cell
Membrane
3
Cell Membrane
The cell membrane is made
of 2 layers of phospholipids
called the lipid bilayer.
Close that window!!!
 There are many reasons we open and shut the
windows in our house.
 Do you want to let all of the bugs and leaves in?
 A window screen provides the protection to keep
unwanted things outside, but it also allows some
things to pass into and out of the room like air,
unpleasant odors, or smoke.
 How does the cell membrane carry out similar
functions to that of a window screen?
The cell membrane
 A cell membrane, like a screen, will let some
things through more easily than others.
 Ex: Air gets through a screen, but insects are
kept out.
 A cell’s membrane is “selectively permeable”. In
other words it allows some things to enter or
leave the cell while keeping other things outside
or inside of the cell.
Solubility
 Materials that
are soluble in
lipids can pass
through the cell
membrane
easily.
7
What determines how particles move in
and out of the cell?
 Which way particles
move depends on the
 a) size of the molecule
or particle,
 B) the path taken
through the
membrane,
c) whether or not
energy is used.
Semipermeable Membrane
Small molecules move through easily.
e.g. O2, CO2, H2O (oxygen, carbon dioxide,
water)
9
Semipermeable Membrane
Molecules larger than water, (such as proteins), do
not move through the membrane on their own.
10
Types of Transport Across
Cell Membranes
11
Moving things “without energy”
 The movement of substances through the
cell membrane “without using energy” is
called passive transport.
 The cell membrane can move things into
and out of the cell without using energy
either by:
 Simple diffusion
 Osmosis
 Facilitated diffusion
Diffusion
Simple Diffusion
 Doesn’t require energy
 Moves from high to low
concentration
 Example: Oxygen or
water diffusing into a cell
and carbon dioxide diffusing
out.
13
Simple Diffusion
 In other words
 Molecules move
from crowded
to
less crowded
areas of
concentration.
 This can occur in
solids, liquids, and
gases.
14
Diffusion “in action”…..
 You might smell perfume when you sit near or walk
past someone wearing it. This is because the
perfume molecules are randomly moving throughout
the air .
 The molecules are going from an area that is
crowded (such as inside the bottle) to a less crowded
area (such as the air itself).
 There’s more space for the molecules to spread out
and move in the air.
 Diffusion stops once there is an equal number of
molecules in both areas.
 The molecules are in equilibrium.
DIFFUSION
Diffusion is a
PASSIVE process
which means no
energy is used to
make the molecules
move, they have a
natural KINETIC
ENERGY
16
Diffusion of Liquids
17
Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient
(HIGH to LOW)
Let’s Take a Look!
 Animation of How Diffusion Works
Osmosis
Diffusion across a membrane
 Diffusion of “water”
across a membrane
 Moves from HIGH
water potential (low
solute) to LOW water
potential (high solute)
 Concentration = the
amount of a substance
in a given volume.
semi-permeable membrane
20
Diffusion of H2O Across A
Membrane
High H2O potential
Low solute concentration
Low H2O potential
High solute concentration
21
Click on Picture for Animation
Practice: Sample 1
10% NaCl
90% H2O
ENVIRONMENT
CELL
20% NaCl
80% H2O
What is the direction of water movement?
23
Practice: sample 2
15% NaCl
85% H2O
ENVIRONMENT
CELL
5% NaCl
95% H2O
What is the direction of water movement?
24
Practice 3….
10% NaCl
90% H2O
ENVIRONMENT
CELL
10% NaCl
90% H2O
NO NET
MOVEMENT
What is the direction of water movement?
The cell is at _______________.
equilibrium
25
Practice 4
40% NaCl
60% H2O
ENVIRONMENT
CELL
20% NaCl
80% H2O
What is the direction of salt (NaCl) movement?
Practice 5
20% NaCl
80% H2O
ENVIRONMENT
CELL
90% NaCl
10% H2O
What is the direction of salt (NaCl) movement?
Wrapping it up...
 1. What is the “fuel” for all cells? ________
 2. Diffusion is the movement of particles from
________ areas of concentration to areas
of __________ concentration.
 3. Osmosis is a specialized type of diffusion
that involves the movement of
___________.
Bellwork questions…..
A simple rule to remember is: salt sucks
Salt is a solute. When it is concentrated inside or
outside the cell, it will draw the water in its direction.
This is also why you get thirsty after eating something
salty!
30% salt
70% water
“container”
100% water
0% salt
“Flower”
The addition of salt
in the container
lowers the
concentration of
water.
The water
concentration is
higher in the cells
of the flower.
What happens when you put salt
on a snail?
 They will shrivel up!!!
 Why?
 The bodies of snails and slugs contain much water in
them. Due to the process of osmosis, in the scenario of
salt and snails, the snails act as the area with high water
concentration. On the other hand, the salt that you add to
the snails has a low water concentration.
 The snails really do not melt when we add salt. They dry
up because too much water in their bodies is sucked out
of them and into the salt. The poor snails shrivel up and
die as a result.
Bellwork
Draw the illustration…
25% NaCl
65% H2O
ENVIRONMENT
CELL
35% NaCl
35% H2O
What is the direction of water movement? Into the cell
What is the direction of the salt (NaCl)? Out of the cell
Explain your answer. Molecules move from areas of high
concentration to lower concentration
What do you think?
A fish that is accustomed to living in salt water is placed
in fresh water. What do you predict might happen to the
cells of the fish?
A. They might shrink up and cause the fish to die.
B. They would become healthier because the water is so
fresh.
C. They might burst and cause the fish to die.
What do you think?
A fish that is accustomed to living in salt water is placed
in fresh water. What do you predict might happen to the
cells of the fish?
A. They might shrink up and cause the fish to die.
B. They would become healthier because the water is so
fresh.
C. They might burst and cause the fish to die.
The process of osmosis would explain the net movement of
water into a cell if the percentage of
A.
B.
C.
D.
water was 90% inside the cell and 95% outside the cell
water was 95% inside the cell and 90% outside the cell
protein was 30% inside the cell and 35% outside the cell
water and protein was equal inside and outside the cell
The process of osmosis would explain the net movement of
water into a cell if the percentage of
A. water was 90% inside the cell and 95% outside
the cell
B. water was 95% inside the cell and 90% outside the cell
C. protein was 30% inside the cell and 35% outside the cell
D. water and protein was equal inside and outside the cell
Facilitated diffusion
(passive transport)
Doesn’t require energy
Uses transport proteins to
move material from high to
low concentration
Examples: Glucose or
amino acids (chain of
proteins) moving from
blood into a cell.
37
Facilitated Diffusion
Molecules will randomly move through the
pores of the cell membrane in protein
channels.
38
Facilitated Diffusion
 Some carrier proteins
do not extend through
the membrane.
 They bond and drag
molecules through the
lipid bilayer and
release them on the
opposite side.
39
Brainpop on “passive transport”
 passive transport
40
BellFUN
 **Fred pours the salty water from his ice cream
maker on the grass in his yard.
 What will happen to the grass and why?
 Finish your diffusion practice sheet so we
can go over it.
Active Transport
Requires energy (or
ATP)
Moves materials from
LOW to HIGH
concentration. It goes
AGAINST the
concentration gradient
42
Moving the “Big Stuff”
Large molecules move materials into the cell by
endocytosis.
43
Endocytosis
It takes in dissolved molecules as a vesicle.
.
This is sometimes called “Cell drinking”.
44
Moving the “Big Stuff”
Exocytosis
- moving
large
things out.
Large molecules are moved out of the cell by vesicles that
fuse with the cell membrane through exocytosis.
This is how many hormones are secreted and how nerve cells
communicate with one another.
Brainpop on active transport
 active transport
Assignment:
 Create your own illustrations of passive transport,
active transport, endocytosis, and exocytosis. Color
and label. Yes, you may use the book as a guide.
46
Bellwork
1. The
arrows in the diagram
represent the direction of movement
of a certain type of molecule
through the cell membrane of two
different cells. The dots represent the
relative concentrations of this
molecule. Which processes are
illustrated in the diagram?
Review
 Happy Science Day! Examine how the particles in
each example are moving and tell if the process is
osmosis, equilibrium, simple diffusion, facilitated
diffusion, or active transport.
1.
2.
48
Examine how the particles in each example are moving and
tell if the process is osmosis, equilibrium, simple diffusion,
facilitated diffusion, or active transport.
3.
4.
Examine how the particles in each example are moving and
tell if the process is osmosis, equilibrium, simple diffusion,
facilitated diffusion, or active transport.
5.