2.4 Movement of Substances

Diffusion - Passive transport, no energy high to low concentration gradient

• size, shape , charge, chemical composition determine movement of substance across membrane

• concentration grad, temp, size, medium, sa distance, pressure all impact diffusion

Facilitated diffusion - Passive transport, no energy high to low concentration gradient, allows quicker movement of substances with the help of a channel/ carrier protein

Osmosis - diffusion of water across semi permeable membrane, low solute to high solute concentration, High to low for molecules concentration gradient,

Hypotonic - hypotonic tonic solution is any external solution that has a low solute concentration and high water concentration compared to outside the cell . In hypotonic solutions, there is a net movement of water from the solution into the cell. gains water, can burst in animals and cell wall stop it from bursting in plants, swells, turgid.

Isotonic - concentration inside the cell is equal to outside the cell , flaccid, equilibrium

Hypertonic - A hypertonic solution has a higher solute concentration compared to the intracellular solute concentration, movement of water out the cell , shrinks.

Active transport - against the concentration gradients, low to high, energy ATP needed, carrier protein binds to substance, ATP binds to binding site ( protein changes shape, substance moves across membrane) proteins reverts to original shape.

SA to V ratio - Larger the surface area of a cell membrane the more efficient the exchange of materials

Bulk transport - used when molecules or substance are too large for membrane

endocytosis - bulk transport into cell

exocytosis - bulk transport out of cell

phagocytosis - solid particles

pinocytosis - liquids

rector mediated endocytosis - specific particles recognised by receptors