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>
Answer:
The missing word is things.
However, the real question is how one material can serve so many purposes? That is what makes it possible for the spiders web to have a high "utility" value?
The answer is in how the spiders make the silk.
Explanation:
So it interesting to note that spiders do not make only one kind of silk. They vary depending on what purpose it's doing serve.
The most common type is Dragline Silk.
Dragline Silk: This contains spidroins. Spidroins fall under a category of a protein called scleroproteins. Because of its composition, a strand or fiber of Dragline has the same tensile strength as steel albeit more flexible. That is if one produced steel the diameter of a spider's silk, and compared both for strength, the silk will be stronger.
The spider produces Dragline silk in its silk glands where they are as viscous as a paste. From here is pulled out or extruded into lines of silk.
Other types of spider silk are:
- Capture-spiral silk. Also known as the Flagelliform, they are used for securing lines of the web. They are adhesive, very elastic, and possess high tensile strength.
- Tubiliform silk: They are also called Cylindriform. Its main use is for the protection of spider eggs. It is used to make a sac for which protects eggs. This type of silk is the toughest.
- Aciniform silk: For preserving fresh prey.
- Minor-ampullate silk: This type is used by spiders for creating temporary support while they are spinning a web. Etc.
Cheers
Sound would travel faster in a thick piece of metal since the molecules are closer together. However, since there are more molecules, it would be quieter on the other side than the hollow metal.
