Which of the following statements about the plasma membrane is INCORRECT?

Question

Examoogle · Accepted Answer

The correct answer is Option C: It is present only in animal cells. The plasma membrane, or cell membrane, is a universal feature of all living cells, serving as the boundary between the internal cytoplasm and the external environment. It is present in both animal and plant cells (as well as bacteria and fungi), making the claim that it is unique to animal cells incorrect.

Step-by-Step Solution & Concepts:
The plasma membrane, or cell membrane, is a universal feature of all living cells, serving as the boundary between the internal cytoplasm and the external environment. It is present in both animal and plant cells (as well as bacteria and fungi), making the claim that it is unique to animal cells incorrect.

Working Principle: The membrane functions based on the Fluid Mosaic Model, where a phospholipid bilayer ($	ext{hydrophilic heads}$ and $	ext{hydrophobic tails}$) is embedded with proteins. It maintains cellular homeostasis through selective permeability, allowing transport of substances via simple diffusion, facilitated diffusion, and active transport (requiring ATP).

Key Formulas: $\Delta G = RT \ln \left( \frac{C_2}{C_1} ight) + zF\Delta \Psi$ — Electrochemical potential gradient driving transport across the membrane

Key Points: The plasma membrane is composed primarily of phospholipids, proteins, and cholesterol.; It is selectively permeable, meaning it controls the movement of ions and organic molecules.; Plant cells possess a plasma membrane located beneath their rigid cell wall.; The fluid nature of the membrane allows for membrane trafficking and cell signaling.

Advantages: Maintains structural integrity; Regulates molecular traffic; Facilitates cell-to-cell communication

Disadvantages: Susceptible to disruption by certain lipophilic toxins or solvents

Applications: Drug delivery systems (liposomes); Osmotic regulation in biotechnology

Additional Info: The plasma membrane thickness is typically about 7–10 $nm$.. Option A is correct: The membrane is a lipid-protein mosaic.. Option B is correct: It acts as a selective filter.. Option D is correct: It encloses cell contents and provides a defined boundary shape.

Answer: C is correct — The plasma membrane is present in all living cells, including plant, animal, and bacterial cells.

Exam Tip: Always remember that while plant cells have a cell wall, they also have a plasma membrane situated just inside the wall; never confuse the two.

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Option A: It is composed of lipids and proteins

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Option B: It is selectively permeable

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Option D: It provides shape to the cell

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