Question

What is the outer covering of typical plant cell? (a) Cell wall externally (b) Plasma membrane externally (c) Cell wall internally (d) Cell wall externally, plasma membrane internally

Short answer

The correct answer is (d) Cell wall externally, plasma membrane internally.

Step-by-step solution

Understanding Plant Cell Structure

A typical plant cell is formed by several parts. The external part is usually called the cell wall, which is a rigid layer giving protection and support to the plant cells. This cell wall is absent in animal cells. Inside the cell wall, there is the plasma membrane, which is responsible for controlling the entry and exit of substances.

Selecting the Correct Answer

Looking at the given options, it is clear that option (d) Cell wall externally, plasma membrane internally correctly defines the outer covering of a typical plant cell.

Key concepts

Cell Wall

Every typical plant cell has a robust outer structure known as the cell wall. This cell wall is primarily composed of cellulose, a carbohydrate which provides durability and strength.
Its main role includes:

• Providing structural support and protection.
• Maintaining the shape of the cell.
• Facilitating communication between cells through small openings called plasmodesmata.

The cell wall is crucial in preventing the cell from bursting in hypotonic environments where water may influx rapidly. Without this layer, plant cells would be vulnerable to damage from external forces and water pressure.

Plasma Membrane

Just beneath the cell wall lies the plasma membrane, a semi-permeable layer critical for cell function. It is composed of a phospholipid bilayer with embedded proteins.
The plasma membrane's primary functions include:

• Regulating the movement of substances in and out of the cell, maintaining homeostasis.
• Serving as the site for cell signaling and communication.
• Allowing cell recognition and interaction through receptor proteins.

While the cell wall provides the form, the plasma membrane ensures that the cell maintains its internal conditions, making it a versatile and essential part of the cell’s covering.

Plant Cell Covering

The plant cell covering consists of two crucial layers: the outer cell wall and the inner plasma membrane. These layers work together to protect the cell and manage the exchange of materials.

Arrangement of Plant Cell Cover

The cell wall is the first barrier and is external, offering both protection and support. Internally, the plasma membrane is delicate and acts as a selective barrier.

Functional Significance

• The cell wall acts like a fortress, providing rigidity and protection.
• The plasma membrane, on the other hand, functions like a gatekeeper, selectively permitting substances to pass in or out.

The combination of these coverings ensures that the plant cell remains healthy, functional, and effectively interacts with its environment.