Carrier-mediated transport uses transporter proteins to move ions or molecules across cell membranes. Uniporters move a single solute in one direction down its concentration gradient. Symporters move two different solutes in the same direction, with one solute moving down its gradient to power the other moving against its gradient. Antiporters move two different solutes in opposite directions, both against their concentration gradients. Glucose absorption in the small intestine uses a sodium-glucose symporter that utilizes the sodium gradient maintained by the sodium-potassium pump to transport glucose into intestinal cells against its concentration gradient.

1. By:
Marwa Nasraldeen Moh. Ali
Carrier
Mediated
Transportes

2. UNIPORTERS
Move single ion or molecule in
one direction across cell membrane
by binding to the molecule or ion and
undergoing conformational change .

3. SYMPORTERS
 Move two different ions or
molecules in the same direction
across cell membrane
simultaneously .
 One solute moves down its
concentration gradient ,and the
energy released used to move the
other solute against its
concentration gradient
 .

4. ANTIPORTERS
● Move two different molecules
or ions in opposite direction
across the membrane .
● They bind to one and
transport it across membrane
while simultaneously binding
to another and transporting it
in the opposite direction.
● Both solutes moved against
their concentration gradient .

5.  In the small intestine nutrients like glucose must first enter the intestinal
cells lining before enter the blood vessels .
Glucose is high conc. inside the cells than in the lumen of the gut ,so
transporting into the cell require energy .
Na conc. gradient is reversed ,much more sodium outside the cell than
inside , this allows glucose -Na pump Symporter to use energy stored in
the Na gradient to pump glucose into the cell
Once in the cell, glucose passes out of the cell down its conc. by passive
movment into the blood by Uniporters
The Na gradient driving the glucose Symporter is maintained by Na-K
pump which keeps the internal conc. of Na low and the external high
The Na-K pump hydrolyse ATP to release the energy to push Na and K
against their conc. gradient.
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