Cell Transport
Section 7.3
Passive Transport - Diffusion
• The movement or
materials across the cell
membrane without
using cellular energy is
called Passive Transport
• Examples:
1) Diffusion
2) Facilitated Diffusion
3) Osmosis
Diffusion
• Diffusion- Process by which particles move an
area of high concentration to an area of lower
concentration.
• Depends on random particle movements.
Facilitated Diffusion
• A process in which molecules that cannot directly
diffuse across the membrane pass through special
protein channels.
Osmosis
Osmosis- Diffusion of water through a selectively
permeable membrane.
Aquaporins- Water channel proteins that allow water to
pass through them.
How Does Osmosis Work?
Active Transport
• Movement of materials
against a concentration
difference.
• Requires energy!
• Transport proteins (protein
pumps)are found in the
membrane carry out small
molecules or ions across the
cellular membrane.
Molecular Transport
• Small molecules and ions
are carried across
membranes by proteins
in the membrane that
act like pumps.
• Many cells use protein
pumps to move calcium,
potassium, and sodium
ions across cell
membranes.
Bulk Transport
• Larger molecules and clumps of material can also be
actively transported across the cell.
• It can take several forms, depending on the size and
shape of material moving in or out of the cell.
• Bulk transport takes on the forms of two different
process:
1) Endocytosis
-Phagocytosis
-Pinocytosis
2) Exocytosis
1)
2)
Endocytosis: Process of taking
material into the cell by means of
infoldings (or pockets) of the cell
membrane
-Phagocytosis: A type of
endocytosis. Extensions of
cytoplasm surround a particle and
package it within a food vacuole.
-Pinocytosis: Cells take up liquid from
the surrounding environment.
Tiny pockets form along the cell
membrane, fill with liquid, and
pinch off to form vacuoles within
the cell
Exocytosis: The membrane of
the vacuole surrounding
the material fuses with the
cell membrane; forcing contents
out of the cell.