Diffusion and Facilitated Diffusion
Diffusion is a fundamental process in biology, involving the movement of particles from areas of high concentration to low concentration. This page explores the key principles of diffusion and introduces the concept of facilitated diffusion.
Principles of Diffusion
Diffusion is characterized by the random motion of particles due to their kinetic energy. This process is passive, requiring no additional energy input. The cell surface membrane's partial permeability plays a crucial role in regulating diffusion.
Definition: Diffusion is the net movement of molecules or ions from a region of higher concentration to one of lower concentration until evenly distributed.
Substances that can diffuse through cell membranes include:
- Lipid-soluble molecules
- Non-polar molecules
- Small molecules like oxygen and carbon dioxide
Highlight: The rate of diffusion is influenced by several factors, including concentration gradient, temperature, surface area, molecule size, and diffusion distance.
Facilitated Diffusion
Facilitated diffusion allows water-soluble, charged ions, and polar molecules to cross the plasma membrane. This process is essential for substances that cannot pass through the hydrophobic fatty acid tails of the membrane.
Vocabulary: Facilitated diffusion utilizes protein channels and carrier proteins to transport molecules across the cell membrane.
Key characteristics of facilitated diffusion:
- It is a passive process
- Occurs down the concentration gradient
- Relies on the kinetic energy of molecules
- Takes place at specific points on the plasma membrane
Example: Glucose, a polar molecule, requires facilitated diffusion to enter cells efficiently.
