Chapter 12

Question 1

two main classes of membrane transport proteins

Answer 1

channels and transporters

Question 2

order of diffusion rate, highest to lowest

Answer 2

small nonpolar molecules
small uncharged polar molecules
larger uncharged polar molecules
ions
nucleic acids

Question 3

membrane protein that undergoes a series of conformational changes to transfer small hydrophilic solutes; have a specific binding site - very selective

Answer 3

transporter

Question 4

membrane protein that acts as a hydrophilic pore through which specific ions or polar inorganic molecules diffuse; select by size and charge

Answer 4

channel

Question 5

Which has a higher rate of diffusion: transporters or channels?

Answer 5

Channels; transporters undergo many conformations to transport one solute while channels allow bulk flow when in open conformation

Question 6

Channels and transporters are part of facilitated diffusion, which means what?

Answer 6

They do not require energy (passive transport), the concentration gradient is the driving factor (high to low)

Question 7

simple diffusion

Answer 7

a type of passive transport: movement of solutes across the membrane driven by concentration, no membrane proteins required

Question 8

active transport

Answer 8

move solutes against concentration gradient; requires energy

Question 9

osmosis

Answer 9

facilitated diffusion: the movement of water down its concentration gradient through aquaporins

Question 10

aquaporins

Answer 10

channels that form pores and allow selective passage of water

Question 11

hypertonic solution

Answer 11

solution has higher solutes than the cell; water flows out of cell

Question 11

hypotonic solution

Answer 11

solution has lower concentration that the cell; water flows into cell

Question 12

glucose transporter

Answer 12

passive transport of glucose into cells from bloodstream; uniport

Question 13

pumps

Answer 13

transporters that require energy for active transport

Question 14

membrane potential

Answer 14

uneven distribution of positive and negative charges across the membrane
-20 to -200mV in cells; -60/-70mV in neurons

Question 15

what are the most plentiful ions on each side of the membrane

Answer 15

Na+ most plentiful outside
K+ most abundant inside

Question 16

electrochemical gradient

Answer 16

driving force that moves electrically charged molecules across membrane; can work with or against concentration gradient

Question 17

types of pumps

Answer 17

gradient driven pump
ATP driven pump
light driven pump

Question 18

gradient driven pump

Answer 18

couples the movement of one solute up gradient to another solute down conc. gradient (symport or antiport)

Question 19

ATP driven pump

Answer 19

couples the movement of one solute up the conc gradient to ATP hydrolysis

Question 20

light driven pump

Answer 20

couples the movement of solute up gradient to light energy (photon)

Question 21

Ca+2 pump

Answer 21

ATPase that returns Ca2+ to sarcoplasmic reticulum in skeletal muscle cells

Question 22

Na+/K+ Pump

Answer 22

ATPase that moves 3 Na+ out of cell and 2 K+ into cell, both against electrochemical gradient
important for maintaining membrane potential

Question 23

symport

Answer 23

gradient driven pump that moves both solutes in the same direction

Question 23

antiport

Answer 23

gradient driven pump that moves solutes in opposite directions

Question 24

Glucose/Na+ symport

Answer 24

uses Na+ gradient to pump glucose into gut epithelial cells

Question 25

glucose transporters function in gut epithelial cells

Answer 25

apical surface: glucose actively transported into cell by glucose/Na+ symport causes high conc of glucose in cell basal/lateral surfaces: glucose uniports passively release glucose into other tissues

Question 26

H+ Pump/ ATPase

Answer 26

creates H+ electrochemical gradient which drives active transport of other solutes found in lysosomes to create acidic internal environment

Question 27

Ion channels

Answer 27

Selectivity filter: depends on diameter and shape of ion channel and charge of amino acids that line it Gated: switch between open and closed conformations based on stimuli

Question 28

Large channels between neighboring cells allow ions and small molecules to move directly from the cytoplasm of one cell into the cytoplasm of neighbor

Answer 28

gap junctions, porins, aquaporins

Question 29

types of gated ion channels

Answer 29

voltage gated ligand gated (extracellular and intracellular) mechanically gated

Question 30

Process of hearing by mechanically gated ion channels

Answer 30

sound vibrations tilt and stretch stereocilia, pulling open ion channels allowing positive ions into stereocilia, and activating hair cells which stimulate auditory nerves to convey signal to brain

Question 31

K+ leak channels

Answer 31

major player in generating resting membrane potential, allows K+ from inside cell to flow out through passive transport, giving inside of cell an even more negative charge

Question 32

patch clamp recording purpose

Answer 32

used to observe the activity of single ion channel

Question 33

patch clamp recording procedure

Answer 33

tight electrical seal formed around one ion channel by a microelectrode patch of membrane detached from cell able to record electrical current passing through membrane channels

Question 34

synapse

Answer 34

site of contact/proximity between two communicating cells

Question 35

synaptic cleft

Answer 35

small space between presynaptic and postsynaptic cells

Question 36

neurotransmitters

Answer 36

chemical signals that bypass the synaptic cleft to transfer and action potential from one cell to the next acetylcholine, epinephrine(adrenaline), glycine, etc

Question 37

patch clamp recording appearance when acetylcholine (aCh) is bound

Answer 37

some peaks indicate periods of open and closed states, not open constantly

Question 38

appearance of patch clamp recording when a signal is not bound

Answer 38

flat line, doesn't open at all

Question 39

patch clamp recording: frequency and amplitude meaning

Answer 39

frequency: stimulus strength (more peaks = higher neurotransmitter concentration) amplitude: number of channels open at the same time

Question 40

Action potential first step

Answer 40

neurotransmitter binds to ligand-gated Na+ channels at the dendrites, allowing Na+ to trickle into cell certain threshold must be reached to start an action potential

Question 41

if large depolarization stimulus reaches the threshold . . .

Answer 41

voltage-gated Na+ channels open and further depolarize the membrane--amplification

Question 42

depolarization during an action potential continues until what

Answer 42

the membrane potential is +40mV, when the electrochemical gradient for Na+ is 0 and the Na+ channels become inactivated

Question 43

primary force of repolarization

Answer 43

voltage gated K+ channel which remains open and K+ flows out of cell

Question 44

inactivation of Na+ channel prevents what

Answer 44

another action potential in that patch of membrane; backward flow of action potential; continuous response to the action potential

Question 45

hyperpolarization

Answer 45

slow closing of K+ channels causes the inside of the cell to become more negative than resting potential, making it harder to depolarize again

Question 46

period when Na+ channel is inactivated

Answer 46

refractory period

Question 47

when the action potential reaches the nerve terminal, it . . .

Answer 47

opens voltage gated Ca2+ channels, allowing Ca2+ to flow into cell

Question 48

influx of Ca2+ at nerve terminal . . .

Answer 48

triggers the fusion of vesicles and release of neurotransmitters into the synapse

Question 49

how are neurotransmitters removed from the synaptic cleft

Answer 49

enzymatic degradation or transporters moving them back into the presynaptic cell

Question 50

acetylcholine receptor

Answer 50

transmitter-gated ion channel in PM of muscle cells, binding of aCh causes side chains to move apart and Na+ can flow through the membrane causing muscle contraction

Question 51

excitatory synapse

Answer 51

excitatory neurotransmitter (acetylcholine) binds, causes depolarization and increases likelihood of action potential

Question 52

inhibitory synapse

Answer 52

inhibitory neurotransmitter (glycine) binds, causing influx of negatively charged Cl- and decreases likelihood of action potential