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
According to widely accepted ‘fluid mosaic model’ cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several respects. In this regard, which of the following statement is incorrect?
Proteins in cell membranes can travel within the lipid bilayer
Proteins can remain confined within certain domains of the membrane
Proteins can also undergo flip-flip movements in the lipid bilayer
Many proteins remain completely embedded within the lipid bilayer
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.
The fluidity of the cell membrane is influenced by several factors. Which of the following would DECREASE membrane fluidity?
Increased proportion of unsaturated fatty acids
Shorter fatty acid chain length
Increased cholesterol content at high temperatures
Decreased cholesterol content at low temperatures
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
Select the incorrect statement about plasma membrane
It is selectively permeable.
It is composed of a phospholipid bilayer.
It contains cholesterol in animal cells.
It is a static structure.
