How is a yeast cell different from an onion skin cell?
a. yeast lacks a cell membrane. an onion skin cell has a cell membrane.
b. yeast doesn't have a cell wall. the onion skin cell has a cell wall.
c. yeast has chloroplasts. the onion skin cell doesn't have chloroplasts.
d. yeast lacks a membrane-bound nucleus. the onion skin cell has one

Answer;

B. Yeast doesn't have a cell wall. The onion skin cell has a cell wall.

Explanation;

-An onion is a multicellular (consisting of many cells) plant organism.As in all plant cells, the cell of an onion peel consists of a cell wall, cell membrane, cytoplasm, nucleus and a large vacuole. The nucleus is present at the periphery of the cytoplasm.

-The vacuole is prominent and present at the center of the cell. It is surrounded by cytoplasm. The presence of a cell wall and a large vacuole are indicators that help identify plant cells, such as seen in the onion peel.

Like bacterial cells, yeast cells have cytoplasm and a membrane surrounded by a cell wall that lacks cellulose, like those of plants.  Yeast cells have a nucleus.They are smaller than animal and plant cells, but slightly larger than bacteria.  

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.