Describe the role that cell membranes play as a highly selective barrier. How are cell membranes involved in active and passive transport? Explain how the cell membrane’s structure relates to its function.

Active transport is the movement of molecules across a cell membrane in the direction against their concentration gradient, going from a low concentration to a high concentration. ... Active transport uses cellular energy, unlike passive transport, which does not use cellular energy.

Passive Transport - Taking the Easy Road

While active transport requires energy and work, passive transport does not. There are several different types of this easy movement of molecules. ... You may also see proteins in the cell membrane that act as channels to help the movement along.

Active transport usually happens across the cell membrane. There are thousands of proteins embedded in the cell's lipid bilayer. Those proteins do much of the work in active transport. ... Only when they cross the bilayer are they able to move molecules and ions in and out of the cell.

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is this for the e2020 class

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