Transcript Crossing the Plasma Membrane

Pretest
• What is the job of the plasma membrane?
• What is semi-permeable?
• What is the difference between active transport
and passive transport?
• What is osmosis?
• What will happen to a cell when placed in a
hypertonic solution? Hypotonic solution?
• What are examples of each?
The plasma membrane maintains
homeostasis for the cell
It is selectively permeable:
It controls what goes into
and out of the cell
Two forms of transport across
the membrane:
Passive Transport
Active Transport
No energy needed
• ENERGY used
• WITH the gradient
(high to low)
• AGAINST the
gradient
• Examples:
• Examples:
– Diffusion
– Osmosis
– Endocytosis
– Exocytosis
Plasma Membrane Structure
Two key components of the membrane:
phospholipids
proteins
Crossing the Plasma Membrane:
Passive Transport
Energy?
Direction?
Examples?
Passive Transport: Diffusion
• The phospholipids line up to
form a double membrane
• Small, uncharged particles
are able to pass right
between the phospholipids
• This is called simple diffusion
Passive Transport: Diffusion
• There are also proteins embedded
between the phospholipids.
• These proteins function as gates,
allowing larger or charged
molecules to get in/out of the cell
• Only molecules which are
“recognized” are allowed thru these
proteins
• This is facilitated diffusion
Passive transport: Diffusion
Concentration gradient:
Higher
Concentration
Lower
Concentration
Molecules collide – pass thru membrane
Passive Transport: Osmosis
• The movement of water
• Water moves TOWARDS the molecules
• Think of it as “water wants to dissolve stuff”
• Which way will water move in each case?
Passive Transport: Osmosis
HYPERtonic
ISOtonic
HYPOtonic
The effect of osmosis on animal
cells
Cytolysis
What do plant cells have
outside of the cell membrane
that animal cells do not have?
What difference will this make
with osmosis?
Effect of osmosis on plant cells
Flaccid -
Turgid
due to
plasmolysis - cell shrinks from cell wall
Passive transport: osmosis
Osmosis
Which way will
water
move?
Hypertonic or Hypotonic?
Active Transport:
Which direction?
Energy Used?
Examples?
Crossing the Plasma
Membrane
Active transport
AGAINST the
gradient
requires
energy
Figure 3.8
Active Transport
• Endocytosis
– Pino– Phago-
• Exocytosis
Ion pumps: Thru a protein, but using energy
Figure 3.9
Crossing the Plasma Membrane
Passive Transport
Active Transport
Crossing the Plasma Membrane
Passive Transport
Active Transport
• No energy needed
• ENERGY used
• WITH the gradient
• AGAINST the gradient
• Diffusion
• Can be through a protein
• Osmosis
• Endocytosis
• Exocytosis
Post test
• What is the job of the plasma membrane?
• What is semi-permeable?
• What is the difference between active transport
and passive transport?
• What is osmosis?
• What will happen to a cell when placed in a
hypertonic solution? Hypotonic solution?
• What are examples of each?