III. Cellular Transport

A. Structure of Plasma Membrane Described as a Fluid Mosaic Many different pieces moving around Parts Phospholipids Two part molecules Polar phosphate head Nonpolar Lipid Tails Form a double layer Non-polar parts stay together

Selectively permeable Hydrophobic (water fearing) molecules pass through Hydrophilic (water loving) molecules bounce off Divides Extracellular fluid from Cytosol

Cholesterol Proteins are Stabilizes the membrane Anchors Name tags Transporters

B. Types of cellular transport Passive transport Requires no energy Two Types Diffusion Osmosis Active transport Requires energy Many types Exocytosis Endocytosis Pumps

C. Diffusion Movement of molecules from an area of high concentration to an area of lower concentration. Why do the molecules move Others bump into them Animation

D. Osmosis Occurs through a barrier Is the diffusion of water Water moves towards area of high solute concentration Solute = What is dissolved Solvent = what its dissolved in

4. Effects of osmosis Tonicity referrers to the solute (salt) Iso- = Same salt Hyper- = Higher salt Hypo- = Lower salt Maintaining tonicity is part of homeostasis Hypotonic Hypertonic Isotonic Lysis Crenated No change

ACTIVE TRANSPORT

E. Exocytosis Movement of objects out of the cell Vesicle binds to the membrane

F. Endocytosis Movement of large objects Cytoskeleton changes membrane shape into a pseudopod (false foot) Vesicle forms around object Object is imported

White blood cell eating a bacterium

G. Receptor Mediated Endocytosis Picky eating Desired object binds to receptors Like a key fits in a lock Vesicle forms when receptors are full

H. Protein Pumps ATP (energy) is used to power the pump Works against diffusion Very important for homeostasis