What is Facilitated Diffusion _ It’s Meaning and Definition Transport of substances across

What is Facilitated Diffusion _ It’s Meaning and Definition Transport of substances across.

 Facilitated Diffusion – Meaning & Definition

Facilitated diffusion is a type of passive transport where molecules move across a cell membrane with the help of specific transport proteins. This process does not require energy (ATP) and helps transport molecules that cannot pass through the lipid bilayer on their own.

 Definition of Facilitated Diffusion:

Facilitated diffusion is the process by which substances move across a biological membrane through specific carrier or channel proteins, following the concentration gradient (from higher concentration to lower concentration) without requiring energy.

 Characteristics of Facilitated Diffusion:

Passive Transport – No energy (ATP) is needed.
Uses Transport Proteins – Helps large, polar, or charged molecules cross the membrane.
Follows Concentration Gradient – Moves from high to low concentration.
Faster than Simple Diffusion – Due to the assistance of proteins.

 Types of Transport Proteins in Facilitated Diffusion:

Carrier Proteins – Bind to specific molecules, change shape, and transport them across.

• Example: Glucose transporter (GLUT) helps glucose enter cells.

Channel Proteins – Form pores or tunnels for molecules to pass through.

• Example: Ion channels (like sodium and potassium channels) help in nerve signaling.

 Examples of Facilitated Diffusion:

Glucose Transport – Glucose enters cells through GLUT transporters.
Ion Transport – Sodium (Na⁺), Potassium (K⁺), and Calcium (Ca²⁺) move through ion channels.
Oxygen & Carbon Dioxide Exchange – Some gases move through aquaporins (water channels).

 Difference Between Simple Diffusion & Facilitated Diffusion:

 Importance of Facilitated Diffusion in Cells:

Helps in nutrient absorption (e.g., glucose in the intestines).
Maintains ion balance (important for nerve signaling and muscle function).
Regulates water movement through aquaporins.

Would you like diagrams or detailed mechanisms for better understanding?

Here’s a clear and complete explanation of Facilitated Diffusion with meaning, definition, and examples — ideal for biology students or competitive exams like NEET, Class 11/12, or general science prep.

What is Facilitated Diffusion?

Definition:

Facilitated diffusion is the passive transport of substances across a cell membrane through specific transport proteins without the use of energy (ATP).

In Simple Words:

Facilitated diffusion is a way for substances like glucose or ions to enter or exit cells with the help of special proteins, even though they can’t pass through the membrane on their own — and it happens without energy use.

Key Features of Facilitated Diffusion:

Feature	Description
Type of Transport	Passive (no energy/ATP required)
Direction	High concentration → Low concentration
Requires Proteins?	Yes (channel or carrier proteins)
Active Transport?	No (opposite of active transport)
Against Gradient?	No (it follows the concentration gradient)

Examples:

1. Glucose transport into muscle cells via GLUT proteins
2. Ion movement (e.g., Cl⁻, Na⁺, K⁺) through ion channels
3. Amino acid uptake in intestinal cells

Types of Facilitating Proteins:

• Channel proteins: Form tunnels (e.g., ion channels)
• Carrier proteins: Change shape to carry molecules across

Difference: Simple vs Facilitated Diffusion

Feature	Simple Diffusion	Facilitated Diffusion
Requires proteins	No	Yes
Type of molecules	Small, non-polar	Large, polar or charged
Example	O₂, CO₂ gases	Glucose, Na⁺, Cl⁻

Summary:

Facilitated diffusion helps essential but large or charged molecules pass through the cell membrane easily and safely — using transport proteins, and without any energy cost to the cell.

Would you like:

• Diagram of facilitated diffusion
• Worksheet or MCQs for practice
• A comparison with active transport

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What is Facilitated Diffusion _ It’s Meaning and Definition Transport of substances across

Lecture 6