IGCSE Biology 0610
3.1 Diffusion
- Diffusion is the net movement of particles from a region of their higher concentration to a region of their lower concentration (down a concentration gradient), as a result of their random movement
- The energy for diffusion comes from the kinetic energy of random movement of molecules and ions
- Some substances move into and out of cells by diffusion through the cell membrane
Importance of Diffusion of Gases & Solutes in Living Organisms
- Gas exchange for respiration
- Obtain requirements
- Get rid of waste materials
Factors that Affect Diffusion
- Surface area – Folded cell membrane = larger surface = allows more molecules to diffuse
- Temperature – Diffusion is faster at warmer temperatures
- Concentration gradient – Cells use substances that diffuse quickly so low concentration in cytoplasm keeps a steep concentration gradient
- Distance – Cell membranes are thin so molecules travel less distance