Summarize how small, nonpolar molecules enter and leave the cell (and why).

Small, nonpolar molecules (ex: oxygen and carbon dioxide) can pass through the lipid bilayer and do so by squeezing through the phospholipid bilayers. They don't need proteins for transport and can diffuse across quickly.

Explanation:

The channel proteins act like doors through the cell membrane.

They allow large polar molecules to move in and out of the cell.

The process is called passive diffusion or passive transport, because it does not need energy.

Sometimes the protein changes shape to help the polar molecules move through the channel.

It often uses a gated pore mechanism, in which the channel is never completely open.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.