A researcher is studying the transport of a novel molecule across a synthetic lipid bilayer. They observe that the molecule moves down its concentration gradient without the need for any membrane proteins or energy input. However, the rate of transport is significantly slower than predicted for simple diffusion. Which of the following BEST explains this observation?
The molecule is very large and its size restricts diffusion through the membrane.
The molecule is charged and is repelled by the hydrophobic core of the bilayer.
The molecule is polar and its passage is hindered by the hydrophobic core of the bilayer.
The molecule is binding to a specific receptor on the membrane surface, slowing its diffusion.
Related Questions
Certain integral membrane proteins facilitate the passage of water across the cell membrane. These proteins are known as aquaporins and are crucial for maintaining cellular water balance. Which of the following is NOT a characteristic of aquaporin-mediated water transport?
Passive transport of water
Saturable transport kinetics
Driven by osmotic gradients
High selectivity for water
The cell membrane maintains a distinct phospholipid composition between its inner and outer leaflets. Which of the following transport mechanisms is primarily responsible for establishing and maintaining this asymmetry?
Simple diffusion
Facilitated diffusion
Flippases
Ion channels
The process by which a cell engulfs large particles or even other cells is called:
Pinocytosis
Exocytosis
Osmosis
Phagocytosis
The fluid mosaic model describes the cell membrane as:
A rigid, static layer
A solid barrier
A dynamic structure with embedded proteins
A single layer of phospholipids
Keeping in view the ‘fluid mosaic model’ for the structure of cell membrane, which one of the following statement is correct with respect to the movement of lipids and proteins from one lipid monolayer to the other (described as flip-flop movement)?
Both lipids and proteins can flip-flop
While lipids can rarely flip-flop, proteins cannot
While proteins can flip-flop, lipids cannot
Neither lipids nor proteins can flip-flop
The thickness of unit membrane is
Choose the correct statements
I. Passive cells are larger in size
II. Larger cells have lower surface volume ratio
III. To remain active, larger cells are either cylindrical in shape or possess several extensions of the cell membrane, like microvilli
IV. Microvilli are found in all those cells, which are active in absorption
V. Microvilli (membrane infoldings) occurs in transfer cells found in plants in the region of absorption or secretion of nutrients
Option containing all correct statements is
I and IV
I, II, III and IV
I, III and II
I, II, III, IV and V
Cell membrane in animals is composed mainly of the molecules of?
Lipids
Proteins
1 and 2
Carbohydrates
Structural lipids of cell membrane are
Simple lipid
Chromolipids
Steroid
Phospholipids
Lipid rafts are specialized microdomains within the cell membrane. Which of the following statements about their composition and function is INCORRECT?
They are enriched in cholesterol and sphingolipids.
They are involved in signal transduction and membrane trafficking.
They exhibit reduced fluidity compared to the surrounding membrane.
They are primarily composed of unsaturated phospholipids and peripheral membrane proteins.
