Download File - Life Science | Mrs. Smith

The Gatekeeper of the Cell
The Cell Membrane
 Cell Membranes surround all cells
 The cell membrane acts as a gate keeper:
 Let some things in & keep some things out
Selective Permeability
 Selectively permeable- some substances can pass
through the membrane while others cannot.
 Permeable- can pass through
 Impermeable- can NOT pass through
1.
2.
3.
Osmosis
Diffusion
Active Transport
Cell Transport
Transport
Passive
Transport=
No energy
Diffusion
Active
Transport =
needs energy
Osmosis
Review
 How would you describe the cell membrane?
a. Rigid
b. Tough
c. Selectively Permeable
d. Impermeable
Passive vs. Active Transport
 The main difference :
 Passive Transport does NOT require energy
 Active Transport does us ENERGY
Passive Transport: Diffusion
 Diffusion: a type of passive transport where molecules
move from high concentration to low concentration.
Diffusion
 Things that move through cell by diffusion:
 food molecules
 oxygen
 water
Passive Transport: Osmosis
 Osmosis: the process that water moves across a cell
membrane high concentration to low concentration.
 Osmosis is the diffusion of water molecules!
Review
 When water moves from high to low concentration it
is known as:
a. Diffusion
b. Magic
c. Osmosis
d. Active Transport
Passive Transport Video
Cell Equilibrium
 Cells always want to maintain balance!
 Sometimes this is bad for the cell
 EX: Blood Cells
Active Transport
 Uses Energy!!!
 Moves molecules in the opposite direction
 Like going uphill
 Examples:
 Transport Proteins
 Engulfing
Transport Proteins
 Proteins in cell membrane “pick up” molecules and
take them inside the cells using energy.
Engulfing
 The cell membrane will surround the molecule and
“swallow” it forming a vacuole.
Review
 What is the difference between active and passive
transport?
a. Active transport requires energy
b. Passive transport requires energy
c. Neither require energy
d. Active transport involves osmosis
Active Transport Video