Warm-Up 1 Is the plasma membrane symmetrical? Why or why not? What types of substances cross the membrane the fastest? Why? Explain the concept of water potential. (Hint: Refer to Lab 1)

Warm-Up 2 What are glycoproteins and glycolipids and what is their function? How do hydrophilic substances cross the cell membrane? Why does water move through the bi-layer quickly?

Warm-Up 3 Side A in a U tube has 5M sucrose and 3 M glucose. Side B has 2 M sucrose and 1 M glucose. The membrane is permeable to glucose and water only. What happens to each side?

Warm-Up 4 Side A in a U tube has 3 M sucrose and 1 M glucose. Side B has 1 M sucrose and 3 M glucose. The membrane is permeable to glucose and water only. What happens to each side?

Cell Transport NOTES Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes.

Passive Transport NO ENERGY needed! Diffusion down concentration gradient (high  low concentration) Eg. hydrocarbons, CO2, O2, H2O

Osmosis: diffusion of H2O

Importance: IMPORT of RESOURCES (nutrients, O2, H2O, etc.) EXPORT of WASTES (CO2, etc.)

External environments can be hypotonic, isotonic or hypertonic to internal environments of cell.

Osmoregulation Control solute & water balance Contractile vacuole: “bilge pump” forces out fresh water as it enters by osmosis Eg. paramecium caudatum – freshwater protist

Facilitated Diffusion 4/15/2017 Facilitated Diffusion Transport proteins (channel or carrier proteins) help hydrophilic or charged substance cross (1) Provide hydrophilic channel or (2) loosely bind/carry molecule across Eg. ions, polar molecules (glucose)

Glucose Transport Protein (carrier protein)

Active Transport Where free energy is used by proteins embedded in membrane to MOVE molecules and / or ions to maintain homeostasis Requires ENERGY (ATP) Proteins transport substances against concentration gradient (low  high conc.) Eg. Na+K+ pumps, proton pumps, endocytosis, exocytosis

Electrogenic Pumps: generate voltage across membrane Na+/K+ Pump Proton Pump Pump Na+ out, K+ into cell Nerve transmission Push protons (H+) across membrane Eg. mitochondria (ATP production)

Eg. sucrose-H+ cotransporter (sugar-loading in plants) Cotransport: membrane protein enables “downhill” diffusion of one solute to drive “uphill” transport of other Eg. sucrose-H+ cotransporter (sugar-loading in plants)

Passive vs. Active Transport Little or no Energy High  low concentrations DOWN the concentration gradient eg. diffusion, osmosis, facilitated diffusion (w/transport protein) Requires Energy (ATP) Low  high concentrations AGAINST the concentration gradient eg. pumps, exo/endocytosis

Bulk Transport Transport of proteins, polysaccharides, large molecules, etc. from the external environment to the internal (and vice versa) Endocytosis: take in macromolecules, form new vesicles Exocytosis: vesicles fuse with cell membrane, expel contents

Endocytosis Cell takes in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane

Types: Phagocytosis: “cellular eating” - solids Pinocytosis: “cellular drinking” - fluids Receptor-Mediated Endocytosis: Ligands bind to specific receptors on cell surface

Exocytosis Internal vesicles fuse with the plasma membrane to secrete large macromolecules out of the cell.

Internal Membranes Eukaryotic cells maintain internal membranes that partition the cell into specialized regions

Functions: Minimize competing interactions Increased surface area where reactions can occur Isolate specific enzymatic reactions Organelles with internal membranes: Endoplasmic Reticulum Mitochondria Chloroplasts Golgi Nuclear Envelope

Archaea and Bacteria Lack internal membranes Have a cell wall