Diffusion Is The Passive Movement Of Particles
- Diffusion is the passive movement of particles in liquids and gases due to their continuous random motion.
- Molecules naturally spread from an area of higher concentration to an area of lower concentration, creating a net movement down the concentration gradient.
- Living organisms do not require energy for diffusion, it is entirely passive.
How Does Simple Diffusion Work?
Definition
Simple diffusion
Simple diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration, down their concentration gradient, without requiring energy (ATP).
- Simple diffusion occurs when particles pass through the phospholipid bilayer of membranes.
- This process is limited to molecules that can permeate the bilayer, such as:
- Non-polar molecules (e.g., oxygen and carbon dioxide), which diffuse easily through the membrane.
- Small polar molecules (e.g., urea and ethanol), which diffuse more slowly.
- Simple diffusion is most effective over short distances, such as across the thin membranes of alveoli or capillaries.
- For larger distances, transport systems like the circulatory system are required.
Role of the Phospholipid Bilayer
- The center of the membrane is hydrophobic, making it challenging for ions and molecules with positive or negative charges to pass through.
- Polar molecules with partial charges diffuse at lower rates, as they are repelled by the hydrophobic core.
If oxygen concentration inside a cell decreases due to aerobic respiration, the higher concentration of oxygen outside the cell drives oxygen to diffuse through the membrane into the cell.
Key Features of Simple Diffusion
- No Energy Required: Diffusion is a passive process, it does not rely on cellular energy (ATP).
