Ch 12 - Transport Across Cell Membranes

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 transport 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 (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 receive 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 on 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 (H+ ATPase)

Answer 11

a protein or protein complex that uses energy supplied by ATP hydrolysis, an ion ingredient, 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

any transmembrane protein that provides a passageway for the movement of select substances across a cell membrane

Question 18

Na+ pump (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

structure at the end of an axon that signals to another neuron or target cell

Question 21

neuron

Answer 21

an electrically excitable cell that integrates and transmits information as part of the nervous system; a nerve cell

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

optogenetics

Answer 23

technique that uses light to control the activity of neurons into which light-gated ion channels have been artificially introduced

Question 24

osmosis

Answer 24

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 25

passive transport

Answer 25

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 26

patch-clamp recording

Answer 26

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 ion in the electrode

Question 27

pump

Answer 27

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 28

resting membrane potential

Answer 28

voltage difference across the plasma membrane when a cell is not stimulated

Question 29

symport

Answer 29

a transporter that transfer two different solutes across a cell membrane in the same direction

Question 30

synapse

Answer 30

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 31

synaptic vesicle

Answer 31

small membrane-enclosed sac filled with neurotransmitter that releases its contents by exocytosis at a synapse

Question 32

transmitter-gated ion channel

Answer 32

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 33

transporter

Answer 33

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

Question 34

voltage-gate channel

Answer 34

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 35

voltage-gated Na+ channel

Answer 35

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