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Transport in Cells
Transport involves the absorption and circulation of materials
throughout an organism.
Absorption – the process whereby the end products of digestion, as well
as other dissolved solids and gases, enter the fluids and the cells of an
organism through the cell membrane (plasma membrane). This is the
beginning part of transport.
Cell Membrane – selectively regulates the entry and exit of materials for
the cell. This helps maintain homeostasis.
In 1972, S.J. Singer came up the first model of a cell membrane.
called the Fluid-Mosaic Model.
Mrs. Degl
It is
It has a phospholipid bilayer in which large proteins are imbedded,
and floating around.
Many small particles, such as amino acids and monosaccharides can
diffuse (pass) through the membrane, while larger molecules such as
proteins and starches cannot diffuse unless they are digested.
The plasma membrane had both passive and active transport.
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Passive Transport
This is movement of materials throughout the plasma membrane
without the use of any cellular energy. Materials are transported
because of the kinetic energy (motion) of the particles that are being
transported. In other words, the cell does not help in diffusion,
materials are already moving as they pass into/out of the cell
membrane.
Diffusion is a form of passive transport.
Diffusion is the process in which the net movement of ions
or materials moves from an area of higher concentration to
lower concentration.
The diffusion of water through a membrane is called osmosis.
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Active Transport
Active Transport is the process in which cellular energy is used to
move particles through a membrane. In this type of transport the
movement goes from an area of lower concentration to an area of
higher concentration. This is the opposite of passive transport.
Carrier membranes embedded in the cell
membrane aid in active transport.
Pinocytosis and Phagocytosis are two types
of active transport.
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Pinocytosis (cell drinking)
This is the process
whereby vacuoles,
formed at the cells
surface, bring in large
dissolved molecules.
These dissolved
molecules are then
broken down by cellular
digestion.
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Phagocytosis (cell eating)
This the process
in which a cell
engulfs
undissolved large
particles by
growing around
them and
enclosing them in
a vacuole.
Mrs. Degl