Cell Membrane and Transport
Cells are the basis of life
• What do they need to survive?
• How do they get the things they need?
Why is this important?
Homeostasis
• The ability of an organism to maintain a
steady, stable internal environment even
when the outside environment is changing
• What do living things regulate?
Cell Membrane
• What does it do?
• What is its structure like?
Cell Membrane
• What is its structure like?
– Phospholipids in a bilayer
– Proteins
– Other stuff
What do membranes do?
• Membranes help transport materials in and
out of the cell
• Selectively permeable
– Only specific things can pass
What do membranes do?
• 3 types of transport
– Passive transport
– Active transport
– Bulk transport
Passive transport
• Does not require energy
• Molecules move from areas of high
concentration to areas of low concentration
Passive Transport – Diffusion
• Some molecules can pass through the
membrane without any assistance
• Like what?
Passive Transport – Facilitated
Diffusion
• Some molecules can cross the membrane with
help from proteins
• Like what?
Passive Transport - Osmosis
• The movement of
water across the
membrane
• Water moves
through special
protein channels
– Aquaporins
Osmosis
• Water moves from high concentration to low
concentration
• The amount of stuff dissolved in the water
determines how the water will move
– Solutions
• Solvent
• Solute
Osmosis
• Osmosis can make cells shrivel or swell based
on the concentration of material around a cell
How does this affect me?
• The cells of living things are surrounded by
water
Active Transport
• Requires energy – ATP
• Moves molecules from areas of low
concentration to areas of high concentration
• Proteins are used to help move the molecules
Bulk Transport
• The cell uses the membrane as a carrier to
move large amounts of materials in or out of
the cell
Exocytosis
• Vesicles made of membrane are used to
transport materials out of the cell
Endocytosis
• Pinocytosis
– Brings fluid and dissolved solutes into the cell
– The cell membrane forms a pocket filled with fluid
Endocytosis
• Phagocytosis
– Brings large particles into the cell
– The cell membrane stretches out to surround a
large object
–