Kapitel 11

Question 1

A large family of membrane transport proteins that use the energy of ATP hydrolysis to transfer peptides or small molecules across membranes. (Figure 11–16)

Answer 1

ABC transporters

Question 2

Membrane protein that responds to binding of acetylcholine (ACh). The nicotinic AChR is a transmitter-gated ion channel that opens in response to ACh. The muscarinic AChR is not an ion channel - but a G-protein-coupled cell-surface receptor.

Answer 2

acetylcholine receptor (AChR)

Question 3

Rapid - transient - self-propagating electrical excitation in the plasma membrane of a cell such as a neuron or muscle cell. Action potentials - or nerve impulses - make possible long-distance signaling in the nervous system. (Figure 11–31)

Answer 3

action potential

Question 4

Movement of a molecule across a membrane or other barrier driven by energy other than that stored in the electrochemical or concentration gradient of the transported molecule.

Answer 4

active transport

Question 5

Glutamate-gated ion channel in the mammalian central nervous system that carries most of the depolarizing current responsible for excitatory postsynaptic potentials.

Answer 5

AMPA receptor

Question 6

Carrier protein that transports two different ions or small molecules across a membrane in opposite directions - either simultaneously or in sequence. (Figure 11–8)

Answer 6

antiporter

Question 7

Channel protein embedded in the plasma membrane that greatly increases the cell’s permeability to water - allowing transport of water - but not ions - at a high rate across the membrane.

Answer 7

aquaporin (water channel)

Question 8

Long nerve cell projection that can rapidly conduct nerve impulses over long distances so as to deliver signals to other cells.

Answer 8

axon

Question 9

Transport protein in the membrane of sarcoplasmic reticulum of muscle cells (and elsewhere). Pumps Ca2+ out of the cytoplasm into the sarcoplasmic reticulum using the energy of ATP hydrolysis.

Answer 9

Ca2+ pump (calcium pump - Ca2+ ATPase)

Question 10

Opens in response to the raised concentration of Ca2+ in nerve cells that occurs in response to an action potential. Increased K+ permeability makes the membrane harder to depolarize - increasing the delay between action potentials and decreasing the response of the cell to constant - prolonged stimulation (adaptation).

Answer 10

Ca2+-activated K+ channel

Question 11

Transmembrane protein complex that allows inorganic ions or other small molecules to diffuse passively across the lipid bilayer. (Figure 11–3)

Answer 11

channel (membrane channel)

Question 12

Photosensitive protein forming a cation channel across the membrane that opens in response to light.

Answer 12

channelrhodopsin

Question 13

Neuronal voltage-gated K+ channel that opens following membrane depolarization but during the falling phase of an action potential due to slower activation kinetics than Na+ channels; opening permits K+ efflux - driving the membrane potential back toward its original negative value - ready to transmit a second impulse.

Answer 13

delayed K+ channel

Question 14

Extension of a nerve cell - often elaborately branched - that receives stimuli from other nerve cells.

Answer 14

dendrite

Question 15

Deviation in the electric potential across the plasma membrane towards a positive value. A depolarized cell has a potential that is positive outside and negative inside.

Answer 15

depolarization

Question 16

Combined influence of a difference in the concentration of an ion on two sides of a membrane and the electrical charge difference across the membrane (membrane potential). Ions or charged molecules can move passively only down their electrochemical gradient.

Answer 16

electrochemical gradient

Question 17

Neurotransmitter that opens cation channels in the postsynaptic membrane - causing an influx of Na+ - and in many cases Ca2+ - that depolarizes the postsynaptic membrane toward the threshold potential for firing an action potential.

Answer 17

excitatory neurotransmitter

Question 18

A supporting non-neural cell of the nervous system. Includes oligodendrocytes and astrocytes in the vertebrate central nervous system and Schwann cells in the peripheral nervous system.

Answer 18

glial cell

Question 19

Neurotransmitter that opens transmitter-gated Cl– or K+ channels in the postsynaptic membrane of a nerve or muscle cell and thus tends to inhibit the generation of an action potential.

Answer 19

inhibitory neurotransmitter

Question 20

Specialized membrane region at the base of a nerve axon (adjacent to the cell body) that is rich in voltage-gated Na+ channels plus other classes of ion channels that all contribute to the encoding of membrane depolarization into action potential frequency.

Answer 20

initial segment

Question 21

Transmembrane protein complex that forms a water-filled channel across the lipid bilayer through which specific inorganic ions can diffuse down their electrochemical gradients. (Figure 11–22)

Answer 21

ion channel

Question 22

K+-transporting ion channel in the plasma membrane of animal cells that remains open even in a “resting” cell.

Answer 22

K+ leak channel

Question 23

A long-lasting (hours or more) decrease in the sensitivity of certain synapses in the brain triggered by NMDA receptor activation. As the opposing process to long-term potentiation - it is thought to be involved in learning and memory.

Answer 23

long-term depression (LTD)

Question 24

Long-lasting increase (days to weeks) in the sensitivity of certain synapses in the brain - induced by a short burst of repetitive firing in the presynaptic neurons. (Figure 11–44)

Answer 24

long-term potentiation (LTP)

Question 25

Transmembrane ion channels that open in response to a mechanical stress on the lipid bilayer in which they are embedded.

Answer 25

mechanosensitive channels

Question 26

Voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other. A typical membrane potential for an animal cell plasma membrane is –60 mV (inside negative relative to the surrounding fluid). (Figure 11–23)

Answer 26

membrane potential

Question 27

Membrane protein that mediates the passage of ions or molecules across a membrane. The two main classes are transporters (also called carriers or permeases) and channels. (Figure 11–4)

Answer 27

membrane transport protein

Question 28

Neurotransmitter receptors that regulate ion channels indirectly through the activation of second-messenger molecules.

Answer 28

metabotropic receptors

Question 29

Type of ABC transporter protein that can pump hydrophobic drugs (such as some anticancer drugs) out of the cytoplasm of eukaryotic cells.

Answer 29

multidrug resistance (MDR) protein

Question 30

Insulating layer of specialized cell membrane wrapped around vertebrate axons. Produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system. (Figure 11–33)

Answer 30

myelin sheath

Question 31

Transmembrane carrier protein found in the plasma membrane of most animal cells that pumps Na+ out of and K+ into the cell - using energy derived from ATP hydrolysis. (Figure 11–15)

Answer 31

Na+-K+ pump (Na+-K+ ATPase)

Question 32

Equation that computes relates the electrical potential (voltage) generated by differences in ion concentrations across a membrane.

Answer 32

Nernst equation

Question 33

Specialized chemical synapse between an axon terminal of a motor neuron and a skeletal muscle cell. (Figures 11–37 and 11–39)

Answer 33

neuromuscular junction

Question 34

Impulse-conducting cell of the nervous system - with extensive processes specialized to receive - conduct - and transmit signals. (Figures 11–28 and 21–66)

Answer 34

neuron (nerve cell)

Question 35

Small signal molecule secreted by the presynaptic nerve cell at a chemical synapse to relay the signal to the postsynaptic cell. Examples include acetylcholine - glutamate - GABA - glycine - and many neuropeptides.

Answer 35

neurotransmitter

Question 36

Subclass of glutamate-gated ion channel in the mammalian central nervous system critical for long-term potentiation and long-term depression. NMDA-receptor channels are doubly gated - opening only when glutamate is bound to the receptor and - simultaneously - the membrane is strongly depolarized.

Answer 36

NMDA receptor

Question 37

Glial cell in the vertebrate central nervous system that forms a myelin sheath around axons. Compare Schwann cell.

Answer 37

oligodendrocyte

Question 38

Use of genetically engineered channelrhodopsin and other light-responsive ion channels and transporters to modulate neuron function and hence analyze the neurons and circuits underlying complex functions - including behaviors in whole animals. (Figure 11–32)

Answer 38

optogenetics

Question 39

A class of ATP-driven pumps comprising structurally and functionally related multipass transmembrane proteins that phosphorylate themselves during the pumping cycle. The class includes many of the ion pumps responsible for setting up and maintaining gradients of Na+ - K+ - H+ - and Ca2+ across cell membranes. (Figure 11–12)

Answer 39

P-type pumps

Question 40

Transport of a solute across a membrane down its concentration gradient or its electrochemical gradient - using only the energy stored in the gradient. (Figure 11–4)

Answer 40

passive transport (facilitated diffusion)

Question 41

Electrophysiological technique in which a tiny electrode tip is sealed onto a patch of cell membrane - thereby making it possible to record the flow of current through individual ion channels in the patch. (Figure 11–34)

Answer 41

patch-clamp recording

Question 42

Neuronal voltage-gated K+ channel - open when the membrane is depolarized - with a specific voltage sensitivity and kinetics of inactivation that induce a reduced rate of action potential firing at levels of stimulation only just above the threshold required - thereby resulting in a firing rate proportional to the strength of the depolarizing stimulus.

Answer 42

rapidly inactivating K+ channel

Question 43

Electrical potential across the plasma membrane of a cell at rest - i.e. a cell that has not been stimulated to open additional ion channels than those that are normally open.

Answer 43

resting membrane potential

Question 44

Glial cell responsible for forming myelin sheaths in the peripheral nervous system. Compare oligodendrocyte. (Figure 11–33)

Answer 44

Schwann cell

Question 45

The part of an ion channel structure that determines which ions it can transport. (Figures 11–24 and 11–25)

Answer 45

selectivity filter

Question 46

Carrier protein that transports two types of solute across the membrane in the same direction. (Figure 11–8)

Answer 46

symporter

Question 47

Communicating cell–cell junction that allows signals to pass from a nerve cell to another cell. In a chemical synapse - the signal is carried by a diffusible neurotransmitter. (Figure 19–22) In an electrical synapse - a direct connection is made between the cytoplasms of the two cells via gap junctions. (Figure 11–34 and 19–23)

Answer 47

synapse

Question 48

Changes in the strength with which a chemical synapse transmits a signal. It is thought to be important in memory formation - where concentrations of postsynaptic AMPA receptor are modulated in response to a synapse’s activity.

Answer 48

synaptic plasticity

Question 49

Transport of solutes - such as nutrients - across an epithelium - by means of membrane transport proteins in the apical and basal faces of the epithelial cells. (Figure 11–11)

Answer 49

transcellular transport

Question 50

Ion channel found at chemical synapses in the postsynaptic plasma membranes of nerve and muscle cells. Opens only in response to the binding of a specific extracellular neurotransmitter. The resulting inflow of ions leads to the generation of a local electrical signal in the postsynaptic cell. (Figures 11–36 and 15–6)

Answer 50

transmitter-gated ion channel (ion-channel-coupled receptor - ionotropic receptor)

Question 51

Membrane transport protein that binds to a solute and transports it across the membrane by undergoing a series of conformational changes. Transporters can transport ions or molecules passively down an electrochemical gradient or can link the conformational changes to a source of metabolic energy such as ATP hydrolysis to drive active transport. Compare channel protein. (Figure 11–3)

Answer 51

transporter (carrier protein - permease)

Question 52

Carrier protein that transports a single solute from one side of the membrane to the other. (Figure 11–8)

Answer 52

uniporter

Question 53

Turbine-like protein machines constructed from multiple different subunits that use the energy of ATP hydrolysis to drive transport across a membrane. The V-type proton pump transfers H+ into organelles such as lysosomes to acidify their interior. (Figure 11–12)

Answer 53

V-type pumps

Question 54

Type of ion channel found in the membranes of electrically excitable cells (such as nerve - endocrine - egg - and muscle cells). Opens in response to a shift in membrane potential past a threshold value.

Answer 54

voltage-gated cation channel

Question 55

Ion channel in the membrane of nerve cells that opens in response to membrane depolarization - enabling K+ efflux and rapid restoration of the negative membrane potential.

Answer 55

voltage-gated K+ channel

Question 56

Ion channel in the membrane of nerve and skeletal muscle cells that opens in response to a stimulus causing sufficient depolarization - allowing Na+ to enter the cell down its electrochemical gradient

Answer 56

voltage-gated Na+ channe