CELL TRANSPORT
How molecules get in and out of cells
We will investigate &
explain the transport of
molecules.
I will be able to explain
the direction molecules
will move in and out of a
cell.
Based on the lab, answer the following
question in CER paragraph format:
Which picture shows Elodea in distilled
water versus Elodea in salt water?
saltwater
solution
We need to move molecules because…
• People need nutrients
• Cells also need
nutrients
• People need to get rid
of waste
• Cells also need to get
rid of waste
What part of the
cell regulates the
entry and exit of
molecules?
The Cell Membrane is made of…
• Proteins and Lipids and some Carbohydrates
https://www.youtube.com/watch?v=LKN5sq5dtW4
The Cell Membrane is Semi-Permeable
• Semi-Permeable means
that only certain sized
molecules can pass
through the cell
membrane
• Think of the cell
membrane as a chain
link fence!
The cell membrane maintains
homeostasis…
• By allowing proper nutrients
into the cell
• By getting rid of wastes from
within the cell
• Membranes also allow cells to
communicate with other cells
& the outside world. This
allows the cells to respond to
their environment & each
other!
Quick Review
• What protective barrier of cells controls the
entry and exit of molecules? What is this
barrier made of?
• The cell membrane is semi-permeable.
Explain what this means.
• How does the cell membrane maintain
homeostasis?
Two Types of Transport
• Cells move substances through the cell
membrane by a process called transport.
1. Passive Transport
Energy
• For small, uncharged molecules
2. Active Transport
• For large molecules
Energy
Diffusion is Passive Transport
• Requires no energy
from the cell
Energy
• Molecules move from
high → low
concentration
• Molecules move with
the concentration
gradient
High
Concentration
Low
Concentration
Examples of Diffusion
• Dye added to liquid
• Odors
In both cases, molecules move from
areas of high concentration to
low concentration
until a balance is reached!
We call this balance on both sides
EQUILIBRIUM!
How does diffusion happen in a cell?
How does diffusion happen in a cell?
Osmosis is the diffusion of water
Cell Membrane
Osmosis is the diffusion of water
Cell Membrane
Water has to be able to move…
• We are over 75% water
• Water is an important solvent in our body
(water dissolves a lot of stuff in our body)
• If our cells are in an environment that robs
them of water, we dehydrate! YIKES!
• Can you die from drinking too much water?
Effects of Passive Transport
80% H2O
80% H2O
80% H2O
100% Distilled Water
80% Water
20% Dissolved
Substances
70% Water
30% Dissolved
Substances
Which way did the water move?
80% H2O
70% Water
30% Dissolved
Substances
Why did the cell get so
small?
Which way did the water move?
80% H2O
80% Water
20% Dissolved
Substances
Why did the cell stay
the same size?
Which way did the water move?
80% H2O
100% Distilled Water
Why did the cell get so
big?
Real life example with red blood cells
A change in cell
shape is a change in
cell function!
Facilitated Diffusion
I’m a
Channel, I
can help!
Channel and carrier proteins help substances
(glucose) pass through the cell membrane. Still
passive transport - no energy required.
Facilitated Diffusion
I’m a
Channel, I
can help!
Channel and carrier proteins help substances
(glucose) pass through the cell membrane. Still
passive transport - no energy required.
Quick Review
• What are the two types of transport and
which one requires the input of ATP energy?
• How is osmosis and facilitated diffusion
different from each other?
• How are hypotonic and hypertonic solutions
different from each other?
Active Transport
• Requires energy from
the cell
Energy
• Molecules move from
low → high
concentration
• Molecules move
against the
concentration gradient
High
Concentration
Low
Concentration
Endocytosis
• Cells take in large particles changing the shape
of the cell membrane.
– Phagocytosis (cell eating)
– Pinocytosis (cell drinking)
Exocytosis
• How the cell gets rid of waste
Quick Review
• What type of transport requires energy and
moves molecules from low to high
concentration?
• What process allows cells to get rid of large
particles like waste?
• What process allows cells to get take in large
molecules?
SUMMARY
Compare Passive Transport to
Active Transport
• ENERGY OR NO ENERGY
• LOW TO HIGH OR HIGH TO LOW
• WITH OR AGAINST CONCENTRATION GRADIENT
http://www.youtube.com/watch?v=wO1yq6YTJDI