Sheets composed of two layers of amphipathic molecules arranged with the hydrophilic groups on the surface and the hydrophobic groups buried in the center that form in water are called A) micelles. B) liposomes. C) vacuoles. D) bilayer membranes. E) none of the above

D) bilayer membranes

Explanation:

Two lipidic bilayers compose the cell membrane. There are also proteins and glucans incrusted in between. Lipids are amphipathic molecules with hydrophilic heads -negatively charged phosphate group- and hydrophobic tails. Lipids are arranged with their hydrophilic polar heads facing the exterior and the interior of the cells, while their hydrophobic tails are against each other, constituting the internal part of the membrane. Membranes are fluid, which means that the composing molecules can move through them.

Lipids can easily change places with other neighboring lipids by lateral diffusion in the same layer. This is passive diffusion, which means that it does not need energy to happen.

Lipids can also diffuse transversally to the other layer but not as easily as lateral diffusion. Jumps between monolayers are infrequent as the lipidic polar heads meet the fatty acid barrier.

There are also other lipidic movements as rotational diffusion that imply the rotation of the molecule.  

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation: