Origin of Eukaryotes

Cytoplasm (inside of cell) Membrane Structure ● The plasma membrane separates the living cell from its nonliving surroundings. (a) Phospholipid bilayer of membrane (b) Fluid mosaic model of Outside of cell Hydrophilic head Hydrophobic tail region of protein regions of Phospholipid bilayer Proteins Cytoplasm (inside of cell)

Membrane Structure

Membrane Structure Phospholipids are amphipathic molecules ● Phospholipid structure Phospholipids are amphipathic molecules

Membrane Structure

Membrane Structure Membrane Models: 1935 Today *Membranes are fluid

Membrane Structure Membranes are fluid

Membrane Structure ● Some functions of membrane proteins Fibers of extracellular matrix Cytoskeleton Cytoplasm Attachment to cytoskeleton and a b Cell signaling c d Enzymatic activity Transport e Intercellular joining f Cell-cell recognition ● Cell surface – Extracellular Matrix

Membrane Structure

Membrane Transport

Membrane Transport Diffusion – a process in which molecules move from an area of high concentration to an area of low concentration Molecules of dye Membrane (a) Passive transport of one type of molecule Net diffusion Equilibrium 11

Membrane Transport Animal cell H2O H2O H2O H2O Normal Lysing Shriveled Plasma membrane Plant cell H2O H2O H2O H2O Flaccid (wilts) Turgid Shriveled (a) Isotonic solution (b) Hypotonic solution (c) Hypertonic solution

Membrane Transport Facilitated diffusion

Membrane Transport Active transport requires energy to move molecules across a membrane. Lower solute concentration Solute ATP Higher solute concentration 14

Membrane Transport *Active transport Example: sodium-potassium pump

Membrane Transport *Voltage *Membrane potential *Some ion pumps generate voltage across membranes Electrogenic pump:

Membrane Transport *Each cell membrane has characteristic set of carrier proteins

Facilitated diffusion Osmosis Higher solute concentration MEMBRANE TRANSPORT Passive Transport (requires no energy) Active Transport (requires energy) Diffusion Facilitated diffusion Osmosis Higher solute concentration Higher water concentration (lower solute concentration) Higher solute concentration Solute Solute Solute Water Solute ATP Lower solute concentration Lower water concentration (higher solute concentration) Lower solute concentration

Traffic of Large Molecules Exocytosis is the secretion of large molecules within vesicles. Outside of cell Plasma membrane Cytoplasm 19

Traffic of Large Molecules Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane. 20

Transport of large molecules Exocytosis Types of endocytosis found in animal cells: Endocytosis *Phagocytosis *Pinocytosis *Receptor-mediated endocytosis