Chapter 7 notes Membrane Structure and Function

Concept 7.1 Most abundant lipids in membranes are ________________. - phospholipids are amphipathic (head is hydrophilic, tail is hydrophobic )

Concept 7.1 Hydrophilic head WATER Hydrophobic tail WATER

Concept 7.1 Phospholipids and proteins are arranged in the “___________________”: membrane is fluid w/ proteins embedded in or attached to the bilayer - disproved the Davson-Danielli “sandwich” model

Concept 7.1 Phospholipid bilayer Hydrophobic regions of protein Hydrophilic regions of protein

Concept 7.1 The membrane is fluid -membranes are not static sheets of molecules locked in place -the membrane is held together primarily by hydrophobic interactions

Concept 7.1 (a) Movement of phospholipids Lateral movement (  10 7 times per second) Flip-flop (  once per month)

Concept 7.1 (b) Membrane fluidity Fluid Unsaturated hydrocarbon tails with kinks Viscous Saturated hydro- carbon tails

Concept 7.1 Membranes are mosaics of structure and function - proteins are embedded in the fluid matrix; the lipid bilayer is the main fabric of the membrane, but proteins determine its specific fcn.

Concept 7.1 Fibers of extracellular matrix (ECM) Glyco- protein Microfilaments of cytoskeleton Cholesterol Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Carbohydrate

Concept 7.1 Two major types of membrane proteins: - _________________: penetrate the hydrophobic core of the bilayer; many are transmembrane proteins - ____________: appendages loosely bound to the surface of the membrane

Concept 7.1 N-terminus C-terminus  Helix CYTOPLASMIC SIDE EXTRACELLULAR SIDE

Concept 7.1 Membrane carbohydrates are important for cell-cell recognition - ____________ is the ability of a cell to distinguish one type of neighboring cell from another - membrane carbohydrates are usually oligosaccharides (can vary greatly)

Concept 7.1 (a) Transport (b) Enzymatic activity (c) Signal transduction ATP Enzymes Signal transduction Signaling molecule Receptor

Concept 7.1 (d) Cell-cell recognition Glyco- protein (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM)

Concept 7.2 Hydrophobic molecules can cross the bilayer with ease. However, ions and polar molecules cannot pass through because they are hydrophilic. - proteins play keys roles in regulating transportation.

Concept 7.2 ________________: allow hydrophilic molecules to enter and exit the cell. The _______________ of a membrane depends on the specific transport proteins built into the membrane.

Concept 7.3 Passive transport involves diffusion across a membrane. - ____________: the tendency for molecules of any substance to spread out into available space - any substance will move down a [gradient]. [high]  [low]

Concept 7.3 Molecules of dyeMembrane (cross section) WATER Net diffusion (a) Diffusion of one solute Equilibrium

Concept 7.3 (b) Diffusion of two solutes Net diffusion Equilibrium

Concept 7.3 ________________: diffusion of a substance across a biological membrane. (no energy is used) Osmosis is the passive transport of water - sln. w/ a higher [solute] = ___________ - sln. w/ a lower [solute] = ____________ - slns. w/ equal [solute] = ____________

Concept 7.3

Organisms without cell walls that live in hypertonic or hypotonic environments must have adaptations for _________________, the control of water balance

Concept 7.3 Organisms with cell walls - ________ (very firm) when placed in a hypotonic sln. - _______ (limp) if the sln. is isotonic - ____________ (shriveled) occurs when put in a hypertonic sln.

Concept 7.3 Hypotonic solution (a ) Animal cell (b ) Plant cell H2OH2O Lysed H2OH2O Turgid (normal) H2OH2O H2OH2O H2OH2O H2OH2O Normal Isotonic solution Flaccid H2OH2O H2OH2O Shriveled Plasmolyzed Hypertonic solution

Concept 7.3 ______________: passive transport of molecules through transport proteins - each protein is specific for the solute it transports

Concept 7.3 EXTRACELLULAR FLUID Channel protein (a) A channel protein Solute CYTOPLASM Solute Carrier protein (b) A carrier protein

Concept 7.4 __________________: movement of molecules across a membrane against the gradient (uses ATP) - sodium-potassium pump: movement of 3 Na + for every 2 K + ions

Concept EXTRACELLULAR FLUID [Na + ] high [K + ] low [Na + ] low [K + ] high Na + CYTOPLASM ATP ADP P Na + P 3 K+K+ K+K+ 6 K+K+ K+K+ 5 4 K+K+ K+K+ P P 1

Concept 7.4 Some ion pumps generate voltage across membranes - membrane potential: the voltage across a membrane - _________________: a transport protein that generates voltage across a membrane (ex. Sodium-potassium pump)

Concept 7.4 The main electrogenic pump for plants and fungi is a ______________ which transports H + ion out of the cell.

Concept 7.4 EXTRACELLULAR FLUID H+H+ H+H+ H+H+ H+H+ Proton pump H+H+ H+H+ + + H+H+ – – – – ATP CYTOPLASM –

Concept 7.4 In ___________, a ATP powered pump can drive the transport of other solutes. 1) active transport of a substance against a gradient 2) cotransport through a protein w/ 2 nd substance

Concept 7.4 Proton pump – – – – – – ATP H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Diffusion of H + Sucrose-H + cotransporter Sucrose

Concept 7.5 ______________: the secretion of macromolecules by the fusion of vesicles with the plasma membrane _______________: the cell takes in macromolecules by forming new vessicles - 3 types: phagocytosis, pinocytosis, and receptor-mediated endocytosis

PHAGOCYTOSIS CYTOPLASM EXTRACELLULAR FLUID Pseudopodium “Food” or other particle Food vacuole Food vacuole Bacterium An amoeba engulfing a bacterium via phagocytosis (TEM) Pseudopodium of amoeba 1 µm Concept 7.5