Biomedical Engineering Reference
In-Depth Information
Diffusion
V
max
Carrier-Mediated Transport
0
0
Substrate
FIGURE 8.20
Comparison of the effect of the amount of substrate and the rate of diffusion and carrier-
mediated transport.
carrier complex on the inside of the membrane. As shown in Figure 8.21, the substrate first
moves to the binding site on the outside of the membrane and binds with the carrier to form
the carrier-substrate complex,
P
o
(left). Next, the carrier-substrate complex moves from the
outside to the inside of the membrane, given by the carrier-substrate complex
P
i
(right). It is
not known how the carrier-substrate complex moves through the membrane, but we are
fairly certain it happens.
The last step is when the carrier-substrate complex,
P
i
, dissociates into the substrate,
S
i
, and carrier, C
i
:
We have assumed that the reaction rates are the same for creation
and the dissociation of the complex,
. In addition, we assume that the reaction of
FIGURE 8.21
Carrier-mediated transport, with the carrier within the membrane. On the left side is the binding
of the carrier with the substrate. On the right side is the substrate released from the binding site into the cell.
