Cell Transport Cell Membrane Controls what materials enter

Cell Transport

Cell Membrane �Controls what materials enter or leave the cell �Also called the phospholipid bilayer �Heads are hydrophilic(“water loving”) � They attract water �Tails are hydrophobic (“water fearing”) � They repel water �Have protein channels to allow larger substances to enter/leave the cell

Cell Membrane

Diffusion �Particles in a solution move along the concentration gradient �Concentration gradient – particles of a solution move from areas of high concentration to low concentration �Uses NO ENERGY!

Osmosis �The diffusion of water across a semipermeable membrane �Goes from high concentration to low concentration �The plasma (cell) membrane undergoes osmosis creating equilibrium in the cell �Equilibrium is reached when both sides of the cell membrane are equal

3 Types of Osmotic Solutions �Isotonic: Equal movement of water molecules across a selectively permeable membrane, no net change in the cell

3 Types of Osmotic Solutions �Hypotonic: Water enters the cell across a selectively permeable membrane to dilute the concentration of macromolecules inside the cell. �Causes the cell to swell

3 Types of Osmotic Solutions �Hypertonic: movement of water out of the cell through the selectively permeable membrane �causes the cell to shrink

Active Transport �Active transport: movement of materials through a membrane from low concentration to high concentration �Going against the concentration gradient �Requires ENERGY!