jakokenno

Jako kenno is a Finnish term that translates to "onion cell" or "onion skin cell." In biology, it refers to the epidermal cells found in the outer layer of an onion bulb. These cells are commonly used in introductory biology and microscopy lessons due to their large size, ease of peeling, and distinct cell wall.

When observed under a microscope, a typical onion epidermal cell exhibits several key features. It is generally rectangular or polygonal in shape. The most prominent structure is the thick cell wall, which provides structural support and protection to the cell. Inside the cell wall is the cell membrane, a thin layer that regulates the passage of substances into and out of the cell. The cytoplasm fills the cell, containing various organelles. A large, central vacuole is a characteristic feature, occupying a significant portion of the cell's volume and storing water, nutrients, and waste products. The nucleus, which contains the cell's genetic material, is often visible as a smaller, denser organelle, typically pushed to the periphery by the large vacuole.

The simple structure and visibility of these organelles make onion epidermal cells an excellent model for teaching fundamental concepts of plant cell biology, including cell structure, the function of organelles, and the differences between plant and animal cells. Their accessibility and robustness allow students to practice techniques such as preparing wet mounts and using a microscope effectively.