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ACTIVE TRANSPORT
This lesson meets the following DoE Specific Curriculum Outcome for Biology 11: 314-1, 314-3, 314-8
ACTIVE TRANSPORT
• Active transport is the
movement of particles
across the cell membrane
against the concentration
gradient with the use of
cellular energy and it
includes endocytosis
and exocytosis.
ACTIVE TRANSPORT
• In active transport, cellular energy is used to
change the shape of a carrier protein so that
required particles move from an area of low
concentration to an area of high concentration.
• Unlike diffusion, particles go against the
concentration gradient.
• It is analogous to rowing a boat upstream
against the current (concentration gradient).
ACTIVE TRANSPORT
• Active transport plays a very important role in
homeostasis. Many molecules needed by the
cell cannot enter the cell through passive
transport because they are too large.
• The cell must use energy to move these
molecules across the plasma membrane.
• There are two types of active transport;
endocytosis and exocytosis.
ENDOCYTOSIS
• Endocytosis is the process used to ingest
materials and bring them inside the cell.
• Due to the fluidity of the plasma membrane it is
able to fold around materials in the external
environment and bring them inside within a
small pouch called a vesicle.
• Once inside the cell these vesicles often fuse
with a lysosome that contains the digestive
enzymes needed to break down the ingested
molecules.
ENDOCYTOSIS
• There are three types of endocytosis:
1. Phagocytosis
2. Pinocytosis
3. Receptor-aided endocytosis
PINOCYTOSIS
• Pinocytosis involves
liquid droplets being
engulfed by the cell.
– The transport of solutes
or fluids.
– Ingesting liquid droplets.
• For example, the cells in
your small intestine
engulf fat droplets by
pinocytosis.
PHAGOCYTOSIS
• Phagocytosis involves
solid particles being
engulfed by the cell.
• The transport of large
particles, whole cells,
or solids.
• Common in unicellular
organisms.
• For example, your white
blood cells engulf foreign
microbes that invade your
blood stream by
phagocytosis.
RECEPTOR-AIDED ENDOCYTOSIS
• Protein receptors (in membrane) hook up with
a specific molecule.
• Indentation in membrane forms and pinches
off inside cell.
EXOCYTOSIS
• A reverse process of endocytosis to get rid of
wastes (indigestible substances) or secrete
hormones.
• The substance is enclosed in a vesicle
(surrounded by a membrane)
• Fuses with cell membrane
• The fused membranes open to let material
outside cell.
EXOCYTOSIS
• Exocytosis is the process used by cells to move
large molecules to the external environment.
• These molecules are often waste products.
• Some molecules released by exocytosis are
products that have been made by that cell and
they are needed elsewhere in the organism. For
example, our nerve cells produce transmitter
chemicals that leave the cells by exocytosis.
EXOCYTOSIS