Download Cell Membrane

Living Environment
Cell Membrane
 Fluid Mosaic Model – It is made up of
a double layer of phospholipids
containing imbedded proteins.
 It controls what can enter and leave the
cell.
 It is a fluid structure…not rigid.
 It is a semipermeable or selective
membrane. Only certain molecules can
pass through. Usually smaller ones can
go through.
Structure of Cell Membrane
Movement Across the Cell Membrane
 1. Active Transport
 requires energy (ATP)
 movement of molecules from an area of
low concentration to high concentration
 Uses carrier proteins embedded in the
cell membrane
Active Transport
 Passive Transport / Diffusion
 Requires no energy
 Movement of molecules from an area of
high concentration to an area of low
concentration
 Establishes a dynamic equilibrium
Diffusion
Osmosis
 Osmosis is the diffusion of water.
 Water moves through gaps between
the phospholipids.
 Concentration of solutes (dissolved
particles) inside and outside of cells
affects osmosis.
Hypertonic Solution
 Concentration of solutes in the solution is greater than
inside the cell.
 Water moves out of cell; cell shrinks.
Isotonic Solution
 Concentration of solutes is the same in the solution
and inside the cell.
 No net movement of water.
Hypotonic Solution
 Concentration of solutes in the solution is less than
inside the cell.
 Water moves into the cell; cell swells.
Osmosis and Solute Concentration
Movement of Large Particles
 Endocytosis –
brings large
particles in by
forming a sac of
membrane
around them
Movement of Large Particles
 Exocytosis –
getting rid of
materials from a
sac at the cell’s
surface