2.4 : Cell Transport
At the end of the lesson, you should be able to :
Explain the various transport mechanisms
across the membrane :
Active transport
- Sodium-Potassium Pump
Endocytosis and Exocytosis
ACTIVE
TRANSPORT …
Require energy…
ACTIVE TRANSPORT…
The movement of a substance across a
cell membrane, with use of energy,
against its concentration
gradient, mediated by specific
transport protein.
ACTIVE TRANSPORT…
Sodium potassium pump
Translocates ions against concentration gradient.
Features :
Protein transportation
between two
conformation.
K+ binding site –
towards cell exterior
Na+ binding site –
towards cytoplasm
ACTIVE TRANSPORT…
Sodium potassium pump
Translocates ions against concentration gradient.
Features :
ATP phosphorylates
the transport protein
powers the
conformational from
Na+ receptive to K+
receptive.
ACTIVE TRANSPORT…
Sodium potassium pump
Binding sites in
the sodium
potassium pump
have high-affinity
to Sodium ions.
ACTIVE TRANSPORT…
Sodium potassium pump
Sodium ions in
cytoplasm bind to
the protein
stimulated
phosphorylation
by ATP.
ACTIVE TRANSPORT…
Sodium potassium pump
Phosphorylation of
ATP causes the
protein to changes it
conformation
ACTIVE TRANSPORT…
Sodium potassium pump
The present of
phosphate group
reduce the affinity of
protein binding sites
to Na+ and now the
proteins binding
sites has higher
affinity to potassium
ions.
Na+ dissociate to
extracellular matrix
and the extracellular
K+ bind to the
protein.
ACTIVE TRANSPORT…
Sodium potassium pump
K+ binding
triggers release
of phosphate
group.
ACTIVE TRANSPORT…
Sodium potassium pump
Loss of phosphate
group restores
protein original
conformation
[high affinity of Na+,
low affinity to K+,
face in cytoplasmic
site.]
ACTIVE TRANSPORT…
Sodium potassium pump
K+ is released into
cytoplasm and Na+
sites will bind with
the Na+
Sodium potassium pump
ACTIVE TRANSPORT…
Involves vesicle formation …
endocytosis
phagocytosis
pinocytosis
exocytosis
ACTIVE TRANSPORT…
Endocytosis
Plasma membrane
invate.
Form small
vesicle/food vacuole.
Phagocytosis –
engulfed large,solid
particle.
Pinocytosis – the
uptake of liquids by
cell.
ACTIVE TRANSPORT…
Phagocytosis
Engulfing cell
detects the
particles.
The particles
attached to the
membrane of
phagocytic cell.
Endocytosis
ACTIVE TRANSPORT… Endocytosis
Phagocytosis
The membrane of cell
invaginate and form
pseudopodia.
Pseudopodia surround
the particle.
Cell engulfing the
particle.
ACTIVE TRANSPORT… Endocytosis
Phagocytosis
Phagosome (food
vacuole) formed.
Phagosome pinched off
and move into the
cytoplasm.
ACTIVE TRANSPORT… Endocytosis
Phagocytosis
Phagosome fused with lysosome to digest the
food particle.
ACTIVE TRANSPORT… Endocytosis
Phagocytosis
• Products absorbed, vacuole disappeared
• Undigested content- egested through reverse prosess
(exocytosis)
ACTIVE TRANSPORT… Endocytosis
Pinocytosis
The cytoplasmic
membrane
invaginates and
pinches off placing
small droplets of
fluid in a pinocytic
vesicle.
ACTIVE TRANSPORT… Endocytosis
Pinocytosis
The liquid contents
of the vesicle is then
slowly transferred to
the cytosol.
Pinocytosis
Involves vesicle formation …
endocytosis
Phagocytosis
e.g. : engulfing
of bacteria by
the
macrophage
exocytosis
Pinocytosis
e.g. : taking of
dissolved solutes by
absorptive cells of
the kidney and
intestines
ACTIVE TRANSPORT…
Exocytosis
The vesicle
membrane
becomes
incorporated into
the cell surface
membrane.
ACTIVE TRANSPORT…
Exocytosis
The contents in the
vesicle are released
outside the cell.
ACTIVE TRANSPORT…
Exocytosis
E.g : The secretion
of enzymes from
pancreatic cells or
hormones from
endocrine glands.
End of Cell Transport