Transcript Active Transport, Exocytosis and Endocytosis

Active Transport,
Exocytosis and
Endocytosis
Chapter 3, Section 5
Of your textbook
Active Transport
Moves substances AGAINST their
concentration gradient

From areas of low concentration to areas of
high concentration
Active Transport Needs Energy
Active transport
is an “uphill”
process (low 
hi) – the opposite
of passive
transport
Therefore, active
transport requires
energy from ATP
Active Transport & Membrane Proteins
Active transport uses
transport proteins, often
called pumps, to move
substances across the
membrane

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These membrane
proteins are integral
proteins – they extend all
the way through the
membrane
They use ATP to pump
molecules / ions against
their concentration
gradients
Transport Proteins
Most transport proteins change shape
when they bond with the target molecule(s).
Some bond to only one type of molecule (=
uniport) and move that molecule in one
direction (animation)
Proton Pump
The proton pump
is an example of a
uniport transport
protein.
This pump is found
in the membranes
of certain
organelles.
It moves protons
(H+) into the
organelle.
Transport Proteins
Others bond to two
types of molecules


May move the
molecules in the
same direction (=
symport)
May move the
molecules in
opposite
directions (=
antiport)
Symport animation
Antiport animation
Sodium-Potassium Pump
click on title for animation
An example of an antiport transport protein.
Moves three sodium ions (Na+) out of the cell for
every two potassium ions (K+) it moves in
Important for re-establishing “normal” conditions
after a nerve impulse / action potential
Endocytosis
click on title for animation on Endo/Exocytosis
A method for bringing large
molecules into a cell
Molecules are engulfed by the
cell membrane.

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A pocket is made around the
substance to be taken in
The pocket breaks off inside the
cell and forms a vesicle
The vesicle fuses with a lysosome
or other organelle
Requires energy from ATP
Phagocytosis
click on title for animation
Type of endocytosis
The cell membrane engulfs larger, solid
particles

Literally means “cell eating”
Example: Amoeba
take in / engulf
their food through
phagocytosis.
Phagocytosis
In the human immune system, some white
blood cells (called macrophages) engulf
and destroy foreign material, such as
bacteria, through phagocytosis
Pinocytosis
Type of endocytosis
The cell takes in fluid (which may also
contain some dissolved substances)

Literally means “cell-drinking”
Example:
Fluid may
cross the
membrane
of a blood
vessel
through
pinocytosis.
Exocytosis
The opposite of endocytosis
Substances are released by
a cell through a vesicle that
carries the unwanted
substance and fuses with
the membrane
Once it fuses with the
membrane, the vesicle
releases the substance
outside the cell
Exocytosis
Neurotransmitters –
chemical signals in your
nervous system - are
released from nerve cell
to nerve cell in this
manner
When the Golgi
apparatus modifies
proteins and sends them
out of the cell, it uses
exocytosis.