The main difference between human cheek cells and onion peel cells is

The correct option is: Presence of cell wall in onion peel cells.

To understand why this is the main difference, let us compare the biological structure of human cheek cells and onion peel cells:

1. Human Cheek Cells (Animal Cells):
Human cheek cells are animal cells. Animal cells are characterized by the absence of a rigid outer cell wall. Instead, their outermost boundary is the flexible, selectively permeable plasma membrane. They contain other eukaryotic organelles such as the nucleus, cytoplasm, mitochondria, and endoplasmic reticulum.

2. Onion Peel Cells (Plant Cells):
Onion peel cells are plant cells. Unlike animal cells, plant cells possess a rigid, supportive outer layer surrounding the plasma membrane, known as the cell wall. The cell wall is composed primarily of cellulose and provides structural support, protection, and shape to the plant cell. Like animal cells, they also contain a plasma membrane, cytoplasm, nucleus, mitochondria, and endoplasmic reticulum.

Comparing the Options:
• Presence of cell wall in onion peel cells: This is correct. Plant cells (onion peel) have a cell wall, while animal cells (human cheek) do not.
• Presence of mitochondria in onion peel cells: Both human cheek cells and onion peel cells contain mitochondria for cellular respiration, so this is not a distinguishing difference.
• Absence of endoplasmic reticulum in cheek cells: Both cell types are eukaryotic and contain endoplasmic reticulum.
• Absence of the plasma membrane in cheek cells: Both cell types possess a plasma membrane.

Therefore, the fundamental structural difference between the two is the presence of a cell wall in the onion peel cells.