The Question is from neet-botany , and it was created by the author B VENKAT

Question

Which type of molecule can easily pass through the cell membrane without assistance?

B VENKAT · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Cell membrane permeability and transport
 **Related Topics**: Lipid bilayer structure, passive transport, diffusion
 **Prerequisites**: Understanding of hydrophobic and hydrophilic interactions, molecular size.
## SOLUTION PATHWAY
**Given Information**:
  The question asks about molecules that can pass through the cell membrane without assistance (i.e., passively).
  The options provide different types of molecules based on size and polarity.
**Method & Steps**:
 1. Analyze the cell membrane structure: The cell membrane is primarily composed of a phospholipid bilayer. The phospholipid tails are hydrophobic (water-fearing) and are oriented towards the interior of the membrane, while the phosphate heads are hydrophilic (water-loving) and face the aqueous environments inside and outside the cell.
  Reasoning:  This hydrophobic core restricts the passage of polar molecules and ions.
  Formula/Rule: None directly applicable, but understanding of hydrophobic and hydrophilic interactions is crucial.
 2. Consider the properties of the molecules in the options:
  Working: 
        * Large, polar molecules: These are hindered by both size and their interaction with the hydrophobic core.
        * Ions: Charged particles, ions are repelled by the hydrophobic core and require channels or transporters.
        * Small, nonpolar molecules: These can easily dissolve in the hydrophobic core and pass through the membrane by simple diffusion.
        * Proteins: Large molecules that require specific transport mechanisms.
  Key Point: Small size and nonpolar nature allow molecules to easily traverse the hydrophobic core of the membrane.
 3. Determine the molecule that can pass through easily:
  Result: Small, nonpolar molecules can easily pass through the cell membrane without assistance.
  Verification: This aligns with the understanding of passive transport mechanisms and the properties of the cell membrane.
 ## OPTION ANALYSIS
A :x: Large, polar molecules are too large and interact strongly with water, preventing easy passage across the hydrophobic core.
B :x: Ions are charged and are repelled by the hydrophobic interior of the membrane, requiring facilitated transport.
C ✓: Small, nonpolar molecules can easily diffuse across the membrane due to their ability to dissolve in the hydrophobic lipid bilayer.
D :x: Proteins are large and complex molecules requiring specific transport mechanisms to cross the cell membrane. 
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing polar and nonpolar molecules: Understanding the difference between hydrophilic and hydrophobic interactions is crucial.
  2.Overlooking the role of size:  Even small polar molecules may have difficulty crossing the membrane.
 **Quick Tips**:
  1.Remember that “like dissolves like”: Nonpolar molecules can easily pass through the nonpolar region of the membrane.
  2.Think about the properties of oil (nonpolar) and water (polar) to help visualize the interactions.

B VENKAT · Answer

Large, polar molecules

B VENKAT · Answer

Ions

B VENKAT · Answer

The correct Option is "Small, nonpolar molecules"

B VENKAT · Answer

Proteins

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