The phrase “too large or too charged” is a helpful way to remember what kinds of molecules need to cross the cell membrane via an intermembrane protein, rather than by crossing directly through the phospholipid bilayer. Describe why some molecules can pass directly through the phospholipid bilayer, while those that are too large or too charged need to pass through a membrane protein.

Due to their hole size.

Explanation:

Some molecules can pass directly through the phospholipid bilayer because of their small size which can easily pass through the small holes of phospholipid bilayer, while those that are too large or too charged need to pass through a membrane protein because membrane protein has a large holes through which large molecules can easily pass through the semi-permeable membrane of the cell by active or passive transport.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.