Question

The boundary of the onion cell is the _______ covered by another thick covering called the cell wall.
A. Cell membrane
B. Cytoplasm
C. Nucleus
D. All of the above

Answer 1

Hint: The epidermal cells of onion are plant cells. Every plant cell has a cell wall. The cell membrane, cytoplasm, and a nucleus present at the periphery of the cytoplasm covered with its own membrane. Onion cells just like all plant cells have a large vacuole.

Complete answer: In every plant cell, the cell membrane is covered by the cell wall which is a rigid wall containing polysaccharides, cellulose, and other proteins. The cell membrane is the selectively permeable membrane whereas the cell wall allows the permeation of almost all the substances. The cytoplasm is a semi-liquid material enclosed by a cell membrane. Organelles like mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, ribosomes, vacuoles, and nucleus are present in the cytoplasm. They have their own membranes making a distinct difference in the content of the cytoplasm and the organelles. The nucleus, also called the controller of the cell, has the genetic material of the cell residing on the periphery of the cytoplasm in the plant cell. The nucleus has a double membrane that protects the DNA and allows the transfer of protein across the cytoplasm and nucleus for the transcription and replication of DNA.
Hence, the correct answer is option (A).

Note: Cell wall is present only in plant cells and not in animal cells and it is the most significant difference between plant cells and the animal cell. Vacuoles are also present in the plant cell in larger sizes unlike in animal cells.