|Cell wall |Class 11th |Chapter |Cell structure and function |

Описание: In biology, the cell wall is a rigid, protective outer layer that surrounds the cell membrane of plant cells, fungi, and some bacteria. Here's an explanation suitable for a Class 11 level:

Composition: The cell wall is primarily composed of cellulose, a complex carbohydrate made up of glucose molecules. In addition to cellulose, it may also contain other substances like hemicellulose, lignin, and pectin, which provide structural support and help in various cell functions.

Functions:

Structural Support: The main function of the cell wall is to provide rigidity and support to the cell. It gives plant cells their shape and prevents them from bursting due to the internal pressure created by the osmotic movement of water.
Protection: The cell wall acts as a barrier that protects the cell from external mechanical damage and pathogens, such as bacteria and fungi.
Regulation of Water Uptake: The cell wall controls the passage of water and solutes into and out of the cell. This selective permeability is crucial for maintaining turgor pressure and preventing wilting.
Types of Cell Walls:

Primary Cell Wall: This is the flexible, thin layer formed during cell growth. It allows the cell to expand and elongate.
Secondary Cell Wall: Some plant cells, like those in wood, develop a secondary cell wall that is thicker and more rigid. It's responsible for the strength of plant structures.
Middle Lamella: This is a layer rich in pectin that holds adjacent plant cells together.
Differences from Animal Cells: Animal cells lack cell walls. Instead, they have a flexible cell membrane that provides shape and structure.

In summary, the cell wall is a crucial feature in plant cells that provides support, protection, and regulation of water movement. It's a distinctive feature that sets plant cells apart from animal cells.