Diffusion in Biology | Biology for GCSE/IGCSE - Year 11 PDF Download

Diffusion in Biology

• Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration. Molecules move down a concentration gradient, as a result of their random movement.
• Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration.

• In living cells, the concept of movement along a concentration gradient remains consistent, but the presence of a cell membrane poses restrictions on the free movement of molecules.
• The cell membrane acts as a semi-permeable barrier, permitting some molecules to pass through easily while impeding others or blocking them entirely.
• The initial form of selection is typically determined by the size of the molecules.
• Diffusion aids living organisms in:
  • acquiring various necessities,
  • eliminating numerous waste substances, and
  • facilitating gas exchange required for respiration.

Examples of diffusion in living organisms 

• Familiarize yourself with instances of substances that organisms acquire through diffusion.
• Remember that plants continually need oxygen for respiration, along with carbon dioxide for photosynthesis under favorable conditions (such as adequate light and appropriate temperature).

Where does the energy for diffusion come from?

• All particles exhibit random movement continuously.
• This phenomenon is termed Brownian motion.
• The kinetic energy derived from this random movement of molecules and ions is the driving force behind diffusion.