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.
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Facilitated Diffusion: Meaning and Definition
Meaning of Facilitated Diffusion
Facilitated diffusion is a passive transport process in which substances move across a cell membrane with the help of transport proteins. Unlike simple diffusion, it requires specific carrier or channel proteins to allow molecules to pass through the lipid bilayer of the membrane.
Definition of Facilitated Diffusion
Facilitated diffusion is the passive movement of molecules across a cell membrane via specific transport proteins, without the use of cellular energy (ATP), following the concentration gradient (from high to low concentration).
Key Features of Facilitated Diffusion:
Passive Transport → No ATP required.
Uses Transport Proteins → Carrier or channel proteins assist movement.
Moves Down the Concentration Gradient → From high to low concentration.
Specificity → Only certain molecules are transported.
Examples of Facilitated Diffusion:
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Glucose Transport → Glucose enters cells through GLUT (Glucose Transporter) proteins.
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Ion Channels → Sodium (Na⁺), Potassium (K⁺), and Calcium (Ca²⁺) move via ion channels.
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Aquaporins → Special channels for water molecules.
Difference Between Simple and Facilitated Diffusion
| Feature | Simple Diffusion | Facilitated Diffusion |
|---|---|---|
| Energy Required? | No | No |
| Transport Proteins? | No | Yes (Carrier/Channel Proteins) |
| Speed | Slow | Faster |
| Example | Oxygen, CO₂ | Glucose, Ions |
Conclusion
Facilitated diffusion is essential for transporting large, polar, or charged molecules that cannot pass through the cell membrane by simple diffusion. It plays a vital role in cellular homeostasis and nutrient absorption.
