Cell Transport Semipermeable membrane – small, lipid-soluble particles can pass, but large, charged particles cannot Diffusion – net movement of particles from high to low concentration Concentration gradient – the difference in concentration between one area and another

Cell Membrane

Diffusion

Osmosis Diffusion of water through aquaporins Moves from high water potential to low water potential. Hypertonic solution – higher solute concentration Hypotonic solution – lower solute conc. Isotonic soln. – solute conc. Equal on both sides and equilibrium.

Osmosis

Facilitated Diffusion Passive transport – no Energy required Moves down concentration gradient Moves through a carrier or channel protein Ex. Glucose Lipid-insoluble substances

Facilitated Diffusion

Active Transport Not passive Goes up or against the concentration gradient (needs energy) Na+ out/K+ in Involves specific carrier proteins Important in muscle contractions, nerve impulses – maintains resting potential Ex. Plant roots, ion pumps

Active Transport – Sodium/Potassium Pump

Endocytosis Enodcytosis – cell taking materials in Pinocytosis – cell drinking Phagocytosis – cell eating

Endocytosis

Receptor-mediated endocytosis

Exocytosis Releasing molecules into the extracellular matrix Bulk flow – passage of substances through vessels or xylem/phloem

Exocytosis

Cell Junctions Plasmodesmata – tunnels between plant cells Junctions in animal cells – tight, anchoring, communicating

Tight, Anchoring and Communicating Junctions