Fluid Mosaic Model & Cell Functions — NEET Biology
📚 Practice ConceptThe fluid nature of the membrane is also important from the point of view of functions like cell growth, formation of intercellular junctions, secretion, endocytosis, cell division etc.
Which of the following statements regarding the plasma membrane and associated processes are correct? S1: The fluid nature of the plasma membrane allows for lateral movement of proteins within the lipid bilayer, contributing to its functionality in endocytosis. S2: In prokaryotic cells, the absence of a flexible plasma membrane, coupled with a rigid cell wall, prevents the process of endocytosis. S3: The plasma membrane of human erythrocytes comprises approximately 52% protein and 40% lipid. S4: Active transport across the plasma membrane involves the movement of molecules along their concentration gradient and does not require ATP utilization. S5: Peripheral proteins are embedded partially or totally in the lipid bilayer, whereas integral proteins lie on the surface of the membrane.
View solution & NCERT explanation
Correct answer: B — S1 and S3 are correct
NCERT core concept: The fluid mosaic model of the plasma membrane and its functions, distinguishing eukaryotic and prokaryotic cell structures. S1: Correct. According to the fluid mosaic model (Singer and Nicolson, 1972), the quasi-fluid nature of lipids enables lateral movement of proteins. This fluidity is important for functions like endocytosis (NCERT page 94). S2: Incorrect. The plasma membrane of prokaryotic cells is structurally similar to that of eukaryotes (NCERT page 90), implying flexibility. However, the rigid cell wall surrounding the plasma membrane in most prokaryotes (except mycoplasma) prevents the cell from performing bulk transport like endocytosis. The statement incorrectly attributes the lack of endocytosis to the "absence of a flexible plasma membrane" itself. S3: Correct. Biochemical investigations revealed that the cell membrane of human erythrocytes has approximately 52% protein and 40% lipids (NCERT page 93). S4: Incorrect. Active transport is an energy-dependent process that moves molecules against their concentration gradient (from lower to higher concentration), utilizing ATP (NCERT page 94). The statement describes passive transport regarding concentration gradient and incorrectly states no ATP is required. S5: Incorrect. Peripheral proteins lie on the surface of the membrane, while integral proteins are partially or totally buried in the membrane (NCERT page 93). The statement swaps the definitions. Therefore, S1 and S3 are correct, while S2, S4, and S5 are incorrect. Recap: The fluid mosaic model explains the structure and various transport functions of the plasma membrane, which differ between prokaryotes and eukaryotes due to structural variations like the cell wall.
What does NCERT say about fluid nature membrane also?
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.