1. The fluid mosaic model of plasma membrane given by Singer and Nicolson is applicable to
(1) only prokaryotic membrane
(2) only eukaryotic membrane
(3) Both prokaryotic and eukaryotic membranes
(4) only to organelle membranes

What is the Fluid Mosaic Model?

The fluid mosaic model of the plasma membrane was proposed by Singer and Nicolson in 1972. It describes the structure of cell membranes as a mosaic of protein molecules floating in a fluid lipid bilayer. This dynamic model revolutionized our understanding of membrane biology.

Key Features of the Model:

• The membrane is semi-permeable.
• Lipids form a bilayer where proteins are embedded.
• Both lipids and proteins can move laterally, making the membrane fluid.
• Integral and peripheral proteins play roles in transport, communication, and structural support.

Applicability of the Fluid Mosaic Model

The big question is: To which types of membranes does this model apply?

Let’s break down the options:

(1) Only Prokaryotic Membranes – ❌ Incorrect

Prokaryotes do have plasma membranes, but the model was not made to exclude eukaryotes.

(2) Only Eukaryotic Membranes – ❌ Incorrect

Eukaryotic membranes do follow the model, but so do prokaryotic ones.

(3) Both Prokaryotic and Eukaryotic Membranes – ✅ Correct

The fluid mosaic model applies to both prokaryotic and eukaryotic plasma membranes. Despite structural differences in complexity, the basic concept of a fluid bilayer with embedded proteins is universal.

(4) Only to Organelle Membranes – ❌ Incorrect

While organelle membranes (like the ER or mitochondria) in eukaryotes also follow this model, it is not limited to them.

Final Answer:

✔️ Option (3) Both prokaryotic and eukaryotic membranes is correct.

Key Takeaways

• The fluid mosaic model is a universal concept in cell biology.
• It is applicable to all biological membranes, including those of prokaryotic and eukaryotic cells.
• It helps explain functions like transport, signaling, and cell integrity.