Download Lesson 3.3 – Passive and Active Transport

• There are 2 main ways that cells transport
nutrients and wastes across the cell
membrane
1. Passive Transport: no energy is used
2. Active Transport: cellular energy is
required
Passive Transport
• There are 3 types of passive transport
1. Simple Diffusion
2. Facilitated Diffusion
3. Osmosis
Simple Diffusion
• The random movement and collision of
molecules in a solution or gas is referred to
as Brownian motion
• Diffusion: molecules move from an area of
high concentration to an area of low
concentration
Simple Diffusion
• This is used to transport small molecules (O2,
CO2, H2O) across the cell membrane, directly
through the lipid bilayer
– Ex. The exchange of O2 and CO2 between the
lungs and the blood vessels
• The amount of O2 in the lungs is HIGH so it moves
into the blood vessels to be carried to the body cells
• The amount of CO2 in the blood vessels is HIGH so it
moves into the lungs and we breathe it out
Facilitated Diffusion
• This is similar to simple diffusion except for
transport proteins (embedded in the cell
membrane) help move material from high
concentration to low concentration
• This type of diffusion is used to move
molecules that are too large to diffuse directly
across the lipid bilayer
– Ex. Glucose, amino acids, etc.
• Diffusion video
http://www.youtube.com/watch?v=VY0mZU
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Osmosis
• Is the diffusion of water (H2O) across the
selectively permeable cell membrane
• Our cells/tissues are surrounded by
environments that contain many different
solutes dissolved in the solvent H2O
– Solute: substance dissolved
in a liquid
– Solvent: liquid in which
substances are dissolved
Osmosis
• Water is small enough to freely cross the cell
membrane but proteins, carbohydrates, lipids
(and their building blocks) are too large to
cross it easily if at all
Osmosis
Osmosis
• Our body cells are surrounded by isotonic
tissue fluid, which has the same
concentration of solutes (sugars, salts,
proteins) as inside of the cell
– Therefore there is equal
movement of water into and
out of the cell or NO net
movement of water into or
out of the cell = equilibrium
Osmosis
• 2 life-threatening situations can occur for cell:
1. HYPOTONIC environment: occurs when there
is less solute, but more H2O outside the cell
than inside
 Water moves into the cell,
the cell enlarges and might
even burst
 Ex. Freshwater fish
constantly pump water out
at the kidneys
Osmosis
• 2 life-threatening situations can occur for cell:
1. HYPERTONIC environment: occurs when there
is more solute, but less H2O outside the cell
than inside
 Water moves out of the cell,
the cell shrinks and could
die
 Ex. Plants growing by salted
roadways get yellow and die
Osmosis video
http://www.youtube.com/watch?v=w3_8FSrq
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Activity and Homework
• Complete questions 7-10 from the Cell
Membrand and Transport PACKAGE
• Read page 50-53
• Answer questions #1, 2a, 3 on page 57