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