What is a comet and where do comets come from?

Explanation:

1. a comet is an icy small solar system body that when passing close to the Sun warms and begins to release gas has a process called outgassing. this produces a visible atmosphere, and sometimes also a tail.

2. comets have two sources. long period comets originate from the Oort cloud. short period comets originate from the Kuiper belt

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.