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Crossing the Cell Membrane
OsmosisActive Transport
Passive transport DiffusionEndo/Exo - Cytosis
Warm Up Questions:
1. All _______________ are composed of cells.
2. New cells are produced from _________________.
3. What is the main purpose of the cell membrane?
4. What are some examples of manmade membranes? (Try to think of at least two.)
Cell Membranes
Made up of a lipid bi-layer
Selectively Permeable: Not all particles can pass through the membrane without help from special membrane proteins
Active Transport
The process by which proteins on the cell membrane push particles from one side of the membrane to the other
Requires energy (ATP)
Occurs when particles are two large to diffuse through a membrane or;
Occurs when particles are moving against the forces of diffusion (Particles are moving from an area of low concentration to an area of high concentration)
Active Transport
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
A B
Na+
Na+
Na+
Na+
Active Transport
Active Transport
Passive Transport
Normal Diffusion that requires membrane proteins Channel ProteinsCarrier Proteins
EndocytosisEndocytosis is the process by which nutrients are
engulfed by the cell membrane
ExocytosisThe process by which a vesicle inside the cell
fuses with the cell membrane and expels its contents outside the cell