A. What is meant by permeability? Permitting passage How about selective permeability? Permitting passage only to a selectively group

B. What element of the membrane makes cell signaling possible? proteins

C. What energy conversion elements are found in membranes? Electron transport and oxidative phosphorylation

A. How does the amphipathic property of fatty acids contribute to the bimolecular structure of membranes? Hydrophobic interaction among repelling ends forces FA to aggregate in bilayer with hydrophobic interior and hydrophilic exterior

B. How are proteins arranged in the lipid bilayer? On surface and embedded in membrane bilayer

C. What functions do proteins play in membranes? Transport, pumps, channels, receptors, enzymes and energy transduction

D. What type of interactions hold membranes together? Hydrophobic, hydrogen bonds, van der waals interactions Are covalent interactions required? no

E. What is meant by the asymmetric property of membranes? Inner and outer face are never the same Which side of this asymmetry has the carbohydrate attached to it? extracellular

F. What does fluidity refer to in membranes? How does flip-flop diffusion compare to lateral diffusion? Flip flop is very slow; lateral is fast

G. What does it mean when a membrane is electrically polarized? Overall net charge of the membrane being negative inside cell and positive outside

A. Which phospholipids are found in membranes? All the above Are any types of phospholipids not found in membranes? No, they just vary in amounts

B. How long are the fatty acids in membranes? 14 to 24 carbons

C. Are any membrane fatty acids saturated? Yes, can be saturated or unsaturated Is the cis or trans form favored in the unsaturated fatty acids? Cis

D. What type of composition favors the formation of bilayered structures as opposed to micelles? What are micelles, anyway? Phospholipids and glycolipids tend to form bilayer; FA tend to form micelle; micelles are spherical structure with hydrophobic core and hydrophilic shell

E. What is meant by self-assembly of membrane structure? no energy or catalyst required

A. What types of specialized functions do proteins contribute to membranes? Insulation of nerve fibers, energy transduction, hormone receptors, pumps and gates

B. Are pumps composed of protein, or lipid, or both? proteins

C. What is an integral membrane protein and how is it distinguished from a peripheral membrane protein? Integral proteins traverse the bilayer membrane; very difficult to remove from membrane; peripheral proteins are attached on surface and can be easily removed with change in pH or temperature

D. What is the feature of an integral protein that allow it to interact with the hydrophobic environment within the membrane? Has a lipophilic domain

E. What are extracellular and intracellular domains? Part of proteins extending beyond membrane to outside of cell or inside of cell

F. How are peripheral proteins attached to membranes? Electrostatic or hydrogen bonds

A. How does the permeability to small ions compare with the permeability of small hydrophobic molecules? Give some examples of each. Almost no ions are permeable except for urea, glycerol, and water; hydrophobic molecules are not permeable.

B. How does the size of polar molecules affect their ability to pass through membranes? Inversely proportional to size How easily does water get through? Freely

C. How does the cell solve the problem of getting the impermeable molecules in and out? Carrier proteins

A. Are they integral or peripheral proteins? integral

B. What's the difference between channel-forming proteins and carrier proteins? Carrier proteins participate in both active and passive diffusion; channel forming is only passive diffusion

C. What does 'thermodynamically downhill' mean? Moving from high concentration gradient to low concentration gradient

D. How does a carrier release a transported molecule on the other side of the membrane? Conformational change

A. What is a uniporter? One way, one molecule Can you give an example of a uniporter? Facilitated diffusion of glucose

B. What are the two types of cotransporters? Antiporter and symporter

C. What is an example of a symporter? Sodium-glucose transport How does that compare with the uniporter example you just looked up? This allows sodium to go in too

D. What is an example of an antiporter? Chloride exchange for bicarbonate in anion channels of RBCs

A. What type of concentration gradients are facilitated diffusion and active transport associated with? Facilitated diffusion from high to low; active diffusion is from low to high

B. What two features do all facilitated diffusion transport proteins have in common? Specificity and affinity for molecules and facilitate in thermodynamically favorable direction

C. Where does the energy to pump ions against a gradient come from? ATP coupling

D. What does the NaÉ - KÉ ATPase pump accomplish? Concentration gradient with negative interior and positive exterior

A. What is the resting membrane potential in mV and is the interior positive or negative across this potential? -60mV; interior is negative

B. How does a leak channel function in establishing the resting membrane potential? Opening of leak channels re-establishes resting membrane potential How much are ion concentrations fluctuating while the membrane pumps are at work? 3 positive molecules out for 2 positive molecules in

A. About how long does the sodium channel remain open? One millisecond How does this affect the membrane potential before the gate closes? Changes potential from -60mV to +30mV

B. What effect does the depolarization of one gated channel have on adjacent gated channels? Causes adjacent ones to open and depolarize

C. How is the resting potential reestablished? Brief opening of leak channels

D. What is meant by a ligand-gated sodium channel? Controlled by neurotransmitter What is an example of such a ligand? acetylcholine