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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really dont know just need some points

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.