The cell membrane is a highly selective barrier that controls the movement of substances in and out of the cell. in fact, polar molecules are unable to go across unless a. they are broken down into smaller pieces. b. they are enclosed in water-filled vesicles. c. they pass through channels in the cell membrane. d. they react with other substances to become nonpolar.

Which sequence correctly shows the path of carbon dioxide during repiration?

Which of the following is a difference between active transport and facilitated diffusion? view available hint(s)which of the following is a difference between active transport and facilitated diffusion? facilitated diffusion can move solutes against a concentration gradient, and active transport cannot.active transport involves transport proteins, and facilitated diffusion does not.facilitated diffusion involves transport proteins, and active transport does not.active transport requires the expenditure of cellular energy, and facilitated diffusion does not.

Plsss > .< compare and contrast the characteristics of flatworms rounds worms and earthworms