Diffusion, Osmosis, and Active Transport

• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
• Diffusion is a passive process - it doesn't require energy.
• Diffusion happens in liquids and gases.
• The bigger the difference in concentration, the faster the diffusion rate.
• Only very small molecules can difffuse through cell membranes. Things like glucose, amino acids, water and oxygen. Big molecules like starch and protein can't fit through the membrane.
• Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
• Tissue fluid surrounds the cells in the body - it's squeezed out of the blood capillaries to supply the cells with everything they need.
• Tissue fluid basically consists of water, oxygen, glucose, and other substances dissolved in it.
• Active transport is the movement of particles against a concentration gradient (from an area of lower concentration to an area of higher concentration) using energy released during respiration.
• Four factors that affect the movement of substances:

  1. Surface area to volume ratio.
  2. Distance.
  3. Temperature.
  4. Concentration gradient.
• The rate of diffusion, osmosis, and active transport is higher in cells with a larger surface area to volume ratio.