Answer:
The two main reasons are nonpolar core of the bilayer and the active transport.
Explanation:
The membrane is structured to have two outer layers that are polar and an inner layer that is nonpolar.
If a membrane protein is exposed to the solvent, i<em>t will also have a polar side. It would be very difficult for the polar face of the membrane to move through the nonpolar core of the bilayer.</em> Therefore, this model is not feasible.
One major form of transport, active transport, moves solutes up the concentration gradient. <em>The binding of a solute and then release on another side of the membrane would only work for facilitated diffusion because it would cause a net movement of solutes down the concentration gradient.</em> It is unclear how energy could be expended to drive this process in the transverse carrier model.<em> Therefore, the transverse carrier model does not explain active transport.</em>
<span>Only one sperm normally fuses
with an egg because if more than one sperm fuses, through a process
called polyspermy, development of the zygote usually stops.
</span>
<span>Fertilization of one egg by
two sperm is possible, but the resulting zygote is almost never viable
because such a zygote would have three sets of chromosomes instead of
the normal two. This condition, called triploidy, is usually
incompatible with life. Those rare triploid infants that do survive to
term have severe and multiple birth defects and rarely live more than a
few days. </span>
The American public owns all federal public lands, including National Parks, National Forests, Wilderness areas, wild and scenic rivers, and wildlife preserves. Every American has a personal stake and a guaranteed say in how these places are cared for.
I also do Acellus :)
Well its easy the Bt gene is inserted into one plant cell by using a bacterial plasma.
