Plant Cell Walls

Questions and Answers

Lignin

Middle lamella (correct)

Primary wall

Secondary wall

Cellulose, hemicellulose, and pectic compounds (correct)

Only lignin

Mineral salts and silica

Lignin and cellulose

It is laid down outside the primary wall.

It is less rigid than the primary wall.

It contains large amounts of lignin. (correct)

It is only composed of pectic compounds.

To maintain the shape and form of the cell Signup and view all the answers

Primary wall Signup and view all the answers

5-10 µm Signup and view all the answers

Study Notes

The cell wall has three fundamental parts: middle lamella, primary wall, and secondary wall.

The primary wall is the first wall formed in a developing cell.
It has a thickness of around 1-3 µm.
The primary wall is more or less elastic and extendable, crystalline, and optically active.
It is composed of cellulose, pectic compounds (mainly polysaccharides), and hemicellulose.

The secondary wall follows the primary wall in development.
It is laid down inside the primary wall.
The secondary wall has a thickness of around 5-10 µm.
It is more or less rigid, crystalline, and strongly optically active.
It is mainly composed of lignin, cellulose, non-cellulosic polysaccharides, hemicelluloses, and mineral salts of Ca, Mg, K, and some silica.

The main role of the cell wall is to form a framework for the cell and prevent over-expansion.
Cellulose fibers, structural proteins, and other polysaccharides help maintain the shape and form of the cell.