Question

Select the correct statements regarding cell membrane in eukaryotic cell.
A. Membrane of human RBCs has approximately 52% protein.
B. Major phospholipids are arranged in a bilayer.
C. Extensions of the plasma membrane into the cell form mesosomes.
D. Tails towards the inner part of lipids are hydrophobic and thus protected from aqueous medium.
E. Glycocalyx is present on the outer surface of the plasma membrane.
Choose the correct answer from the options given below :

• A. C, D and E only
• B. B, C and E only
• C. A, C and E only
• D. A, B and D only

Hint:

Logic Tip: Mesosomes are the "mitochondria equivalents" for bacteria. If you remember that mesosomes equal prokaryotes, you immediately know Statement C is false. This eliminates options 1, 2, and 3 instantly!

Answer 1

The Correct Option is D

Concept:
The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character. Understanding the specific composition and features of the eukaryotic cell membrane is essential to evaluate the statements.
Step 1:
Chemical studies on the erythrocyte (red blood cell) membrane show that it contains approximately 52% protein and 40% lipids. This detailed biochemical analysis supports the fluid mosaic model. Statement A is correct.
Step 2:
The basic structural framework of the plasma membrane is the lipid bilayer. The major lipids are phospholipids that are arranged in a bilayer structure. Statement B is correct.
Step 3:
Mesosomes are formed by the extension of the plasma membrane into the cell. However, mesosomes are a characteristic feature of prokaryotic cells (like bacteria), where they aid in respiration, secretion, and increasing surface area. They are absent in eukaryotic cells. Statement C is incorrect.
Step 4:
In the lipid bilayer, the phospholipids are arranged with their polar (hydrophilic) heads facing outwards towards the aqueous environments (extracellular fluid and cytoplasm), while their non-polar (hydrophobic) tails, composed of saturated hydrocarbons, face the inner part of the membrane. This arrangement protects the hydrophobic tails from the aqueous medium. Statement D is correct.
Step 5:
The glycocalyx is an outermost layer consisting of glycoproteins and glycolipids. While it is present on the outer surface of the plasma membrane in some eukaryotic cells (like animal cells), it is primarily defined as the outermost envelope layer in bacterial (prokaryotic) cells, lying outside the cell wall. The statement as written is generally used to describe the bacterial envelope in NCERT texts. Because the question specifically asks about the eukaryotic cell membrane, and statements A, B, and D are unequivocally correct standard textbook facts for eukaryotes, we must rely on the provided options. Let's look at the options.
Step 6:
Statements A, B, and D are definitively correct descriptions of the eukaryotic cell membrane as per standard biology curricula. Option (4) includes exactly these three statements.