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

Step 1 : Understanding the Question:
The question asks to identify correct statements about the composition, structure, and specialized features of the eukaryotic cell membrane (plasma membrane). This involves understanding the fluid mosaic model, the nature of phospholipids, and cell-type specific structures.
Step 2 : Key Formulas and Approach:
The approach involves checking each statement against the Fluid Mosaic Model of Singer and Nicolson:
1. Biochemical composition of specialized cells (RBCs).
2. Standard phospholipid bilayer organization.
3. Differentiating prokaryotic structures (Mesosomes) from eukaryotic ones.
4. The amphipathic nature of the lipid bilayer.
5. Identifying cell surface coatings and their typical host cells.
Step 3 : Detailed Explanation:

Statement A: Detailed biochemical studies of the human erythrocyte (RBC) membrane have demonstrated that it is composed of approximately 52% protein and 40% lipid. While these percentages vary by cell type, this is a standard benchmark for RBCs. Thus, this statement is correct.

Statement B: The fundamental structural unit of the cell membrane is the phospholipid bilayer. These lipids are arranged such that they form a continuous stable framework for the membrane proteins. This statement is correct.

Statement C: Mesosomes are indeed specialized extensions of the plasma membrane into the cell, but they are a hallmark feature of prokaryotic (bacterial) cells. Eukaryotic cells do not possess mesosomes. Thus, this statement is incorrect.

Statement D: Phospholipids are amphipathic, containing both polar and non-polar regions. The polar "heads" face the outer aqueous environment, while the hydrophobic tails face each other in the membrane's interior. This arrangement ensures the tails are protected from the water. This statement is correct.

Statement E: While a glycocalyx is found on many animal cells, it is primarily emphasized in biological texts as the outermost component of the bacterial cell envelope. Given the strict definitions in standard curricula, it is usually not grouped with core "eukaryotic" membrane facts.

Step 4 : Final Answer:
Statements A, B, and D are standard and correct descriptions of the eukaryotic cell membrane. Thus, the correct combination of statements is found in option (D).