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Active Transport
MOVING MOLECULES ACROSS THEIR CONCENTRATION GRADIENT
Active Transport
Moving molecules against their concentration gradient is known as Active Transport.
Energy is required because molecules are being pumped against their concentration
gradient
Proteins that work as pumps are called protein pumps.
These protein pumps are membrane bound receptors.
Moving Against the Concentration Gradient
The cell uses energy in the form of ATP to transport molecules across the membrane.
What is ATP?
Low
High
ATP- Adenosine Triphosphate
Breaking off one of the
three phosphates creates
energy to be used by the
cell.
ATP
ADP+ P + Energy
Sodium-Potassium Pump
 Antiporter- membrane transport
protein that simultaneously
transports two different molecules
across a membrane in opposite
directions.
 3 Na+ out of cell / 2 K+ into cell
 Major contributor for (-) resting
membrane potential
Requires Energy
Proton Pump
Uses ATP energy to
pump Hydrogen
molecules across the cell
membrane
Aids in membrane
potential being slightly (-)
Requires Energy
Endocytosis
A process by which cells ingest external fluid, macromolecules, and large
particles.
• Vesicles- membrane bound organelle
• Pinocytosis- involves transport of solutes or fluids.
• Phagocytosis- involves transport of large particles.
Requires
Energy
Exocytosis
A process that moves
intracellular vesicles outside the
cell.
• Proteins are made in
ribosomes, packaged in the
Golgi apparatus and then
transported to the cell surface
by vesicles.
Requires Energy
Homeostasis
The tendency of an organism or cell to maintain internal stability.
What does membrane transport have to do with homeostasis?
Negative Feedback
Release of an initial
hormone stimulates
release or production of
other hormones or
substances that inhibit
further release of the
initial hormone.
Most hormone systems
use negative feedback
Ex. Thermostat
Positive Feedback
Release of an initial hormone
stimulates release or
production of other hormones.