Chapter 12

Question 1

action potential

Answer 1

Traveling wave of electrical excitation caused by rapid,
transient, self-propagating depolarization of the plasma
membrane in a neuron or other excitable cell; also called
a nerve impulse.

Question 2

active transport

Answer 2

The movement of a solute across a membrane against its
electrochemical gradient; requires an input of energy, such
as that provided by ATP hydrolysis.

Question 3

antiport

Answer 3

Type of coupled transporter that transfers two different
ions or small molecules across a membrane in opposite
directions, either simultaneously or in sequence.

Question 4

axon

Answer 4

Long, thin extension that conducts electrical signals away

from a nerve cell body toward remote target cells.

Question 5

Ca2+ pump (or Ca2+ ATPase

Answer 5

An active transporter that uses energy supplied by ATP

hydrolysis to actively expel Ca2+ from the cell cytosol.

Question 6

channel

Answer 6

A protein that forms a hydrophilic pore
across a membrane, through which
selected small molecules or ions can
passively diffuse.

Question 7

dendrite

Answer 7

Short, branching structure that extends from the surface of

a nerve cell and receives signals from other neurons.

Question 8

depolarization

Answer 8

A shift in the membrane potential, making it less negative

on the inside of the cell.

Question 9

electrochemical gradient

Answer 9

Driving force that determines which way an ion will move
across a membrane; consists of the combined influence
of the ion’s concentration gradient and the membrane
potential.

Question 10

gradient-driven pump

Answer 10

A protein that uses energy stored in the electrochemical
gradient of ions to actively transport a solute across a
membrane.

Question 11

H+ pump (or H+ ATPase

Answer 11

A protein or protein complex that uses energy supplied by
ATP hydrolysis, an ion gradient, or light to actively move
protons across a membrane.

Question 12

ion channel

Answer 12

Transmembrane protein that forms a pore across the lipid
bilayer through which specific inorganic ions can diffuse
down their electrochemical gradients.

Question 13

K+ leak channel

Answer 13

Ion channel permeable to K+ that randomly flickers between
an open and closed state; largely responsible for the resting
membrane potential in animal cells.

Question 14

ligand-gated channel

Answer 14

An ion channel that is stimulated to open by the binding of

a small molecule such as a neurotransmitter.

Question 15

mechanically-gated channel

Answer 15

An ion channel that allows the passage of select ions across
a membrane in response to a physical perturbation.

Question 16

membrane potential

Answer 16

Voltage difference across a membrane due to a slight
excess of positive ions on one side and of negative ions on
the other.

Question 17

membrane transport protein

Answer 17

Transporter found in the plasma membrane of most animal
cells that actively pumps Na+ out of the cell and K+ in using
the energy derived from ATP hydrolysis

Question 18

Na+ pump (or Na+-K+ ATPase

Answer 18

Transporter found in the plasma membrane of most animal
cells that actively pumps Na+ out of the cell and K+ in using
the energy derived from ATP hydrolysis

Question 19

Nernst equation

Answer 19

An equation that relates the concentrations of an inorganic
ion on the two sides of a permeable membrane to the
membrane potential at which there would be no net
movement of the ion across the membrane

Question 20

nerve terminal

Answer 20

Small signaling molecule secreted by a nerve cell at a
synapse to transmit information to a postsynaptic cell.
Examples include acetylcholine, glutamate, GABA, and
glycine.

Question 21

neuron

Answer 21

Small signaling molecule secreted by a nerve cell at a
synapse to transmit information to a postsynaptic cell.
Examples include acetylcholine, glutamate, GABA, and
glycine.

Question 22

neurotransmitter

Answer 22

Small signaling molecule secreted by a nerve cell at a
synapse to transmit information to a postsynaptic cell.
Examples include acetylcholine, glutamate, GABA, and
glycine.

Question 23

osmosis

Answer 23

Passive movement of water across a cell membrane from
a region where the concentration of water is high (because
the concentration of solutes is low) to a region where the
concentration of water is low (and the concentration of
solutes is high).

Question 24

passive transport

Answer 24

The spontaneous movement of a solute down its
concentration gradient across a cell membrane via a
membrane transport protein, such as a channel or a
transporter.

Question 25

patch-clamp recording

Answer 25

Technique used to monitor the activity of ion channels in a
membrane; involves the formation of a tight seal between
the tip of a glass electrode and a small region of cell
membrane, and manipulation of the membrane potential
by varying the concentrations of ions in the electrode

Question 26

pump

Answer 26

Transporter that uses a source of energy, such as ATP
hydrolysis or sunlight, to actively move a solute across a
membrane against its electrochemical gradient.

Question 27

resting membrane potential

Answer 27

Voltage difference across the plasma membrane when a

cell is not stimulated

Question 28

symport

Answer 28

A transporter that transfers two different solutes across a

cell membrane in the same direction.

Question 29

synapse

Answer 29

Specialized junction where a nerve cell
communicates with another cell (such as
a nerve cell, muscle cell, or gland cell),
usually via a neurotransmitter secreted by
the nerve cell

Question 30

synaptic vesicle

Answer 30

Small membrane-enclosed sac filled with neurotransmitter

that releases its contents by exocytosis at a synapse.

Question 31

transmitter-gated ion channel

Answer 31

Transmembrane receptor protein or protein complex that
opens in response to the binding of a neurotransmitter,
allowing the passage of a specific inorganic ion; its
activation can trigger an action potential in a postsynaptic
cell.

Question 32

transporter

Answer 32

Membrane transport protein that moves a solute across a
cell membrane by undergoing a series of conformational
changes.

Question 33

voltage-gated channel

Answer 33

Channel protein that permits the passage of selected ions,
such as Na+, across a membrane in response to changes
in the membrane potential. Found primarily in electrically
excitable cells such as nerve and muscle cells.

Question 34

voltage-gated Na+ channel

Answer 34

Protein in the plasma membrane of electrically excitable
cells that opens in response to membrane depolarization,
allowing Na+ to enter the cell. It is responsible for action
potentials in these cells