Diffusion

• Diffusion: The net movement of particles from an area of high concentration to an area of low concentration.
• Osmosis: The diffusion of water molecules across a partially permeable membrane, which can be affected by the solute concentration on either side of the membrane.
• Diffusion: To spread something out
• Higher concentration in particles: all bunched up
• Lower concentration in particles: more space between them
• Partially permeable membranes allow some substances through but not others
• Diffusion is a passive process, where particles move down from an area of high concentration to an area of low concentration.
• Passive process : A process that does not require energy input from the surroundings.
• Osmosis is a special case of diffusion : the net movement of water molecules
• active transport is the movement of molecules from a low concentration to a high concentration across a cell membrane against a concentration gradient
• Active transport : An area of lower concentration to an area of higher concentration
• Active transport requires enegry from the cell
• Active transport requires energy from cellular respiration
• larger organisms have less surface area compared to their volume
• Specialised Exchange Surfaces features: Large surface area, Surfaces are very thin, Surfaces are permeable, Good supply of blood (internal medium) and good supply of extrernal medium
• exchange surface: A part of an organism over which substances are exchanged with the environment