Question

Which is the outermost structure of cell wall?

• A. Primary wall
• B. Secondary wall
• C. Tertiary wall
• D. Middle lamella, if present.

Answer 1

The correct option is D Middle lamella, if present.

• The cell wall in plants and few algae consists of three important layers:
  

1) The primary cell wall is the outermost thin, flexible and extensible layer.

2) The secondary cell wall is a thick layer present inside the primary cell wall.

3) The middle lamella is a layer rich in pectins which form plasmodesmata connections between adjacent cell walls.

• This layer cements the cell walls of two adjacent plant cells.
• It is the first formed outermost layer (cell plate formed during cell division forms the middle lamella or lamellum).
  
• So, the correct answer is 'Middle lamella, if present'.