The Neuronal Membrane at Rest

Question 1

action potential

Answer 1

— spike, discharge, nerve impulse
— a brief fluctuation in membrane potential caused by the rapid opening and closing of voltage-gated ion channels
— “information is encoded in the pattern of electrical impulses”

Question 2

excitable membrane

Answer 2

— any membrane with the capability of generating axon potentials

Question 3

resting membrane potential

Answer 3

— the membrane potential (membrane voltage) maintained while a cell is not generating action potentials
— ≈ -65 mV

Question 4

polar covalent bond

Answer 4

— a covalent bond where electrons are unequally shared
— example: H20 provides more electrons to oxygen’s outermost shell, making it polar, and thus making it a solvent of ionic substances

Question 5

ion

Answer 5

— an atom or molecule with a net electrical charge due to difference in number of protons (atomic number) and electrons

Question 6

ionic bond

Answer 6

— complete transfer of valence electrons between atoms, resulting in two oppositely charged ions

Question 7

sphere of hydration

Answer 7

— “cloud” of water molecules surrounding ions in a solution, effectively insulating ions from one another

Question 8

cation v. anion

Answer 8

— cations have net positive charges: Na+ and K+ (monovalent cations), and Ca2+ (divalent cation)
— anions have net positiv charges: Cl- (monovalent anion)

Question 9

nonpolar covalent bond

Answer 9

— occurs when shared electrons are distributed evenly, giving a substance no net electrical charge

Question 10

lipids

Answer 10

— class of water-insoluble biological molecules important to the structure of cell membranes

Question 11

phospholipids

Answer 11

— lipids containing long nonpolar chains of carbon atoms bonded to hydrogen atoms, with a polar phosphate group

Question 12

phospholipid bilayer

Answer 12

— arrangement of phospholipid molecules forming the basic structure of the cell membrane

Question 13

R group

Answer 13

— substituent of amino acids determining the chemical relationships in which the amino acid can participate

Question 14

peptide bond

Answer 14

— covalent bond between the amino group (NH3+) of one amino acid to the carboxyl group (COO-) of another
— synthesizes one water molecule

Question 15

polypeptide

Answer 15

— a string of amino acids held together by peptide bonds

Question 16

protein structure I

Answer 16

— “primary”

— the sequence of amino acids in the polypeptide

Question 17

protein structure II

Answer 17

— “secondary”

— coiling of a polypeptide into an alpha helix (α-helix)

Question 18

protein structure III

Answer 18

— “tertiary”

— three-dimensional folding of a polypeptide

Question 19

protein structure IV

Answer 19

— “quaternary”

— different polypeptides bonded together to form a larger protein

Question 20

subunit

Answer 20

— each polypeptide contributing to the quaternary structure of a large protein
— subunit composition variations determine channel properties

Question 21

ion channels

Answer 21

— a membrane-spanning protein forming a pore and allowing the passage of ions from one side of the cellular membrane to the other
— typically requires 4-6 protein molecule subunits

Question 22

ion selectivity

Answer 22

— a property of most ion channels , specified by pore diameter and R group nature
— creates selective permeability towards specific ions

Question 23

gating

Answer 23

— property of ion channels where opening or closing occurs in response to specific signals, such as membrane voltage or neurotransmitter presence

Question 24

ion pumps

Answer 24

— enzymes using energy released from ATP breakdown to transport certain ions across the membrane

Question 25

diffusion

Answer 25

— temperature-dependent movement of molecules from high concentration to low concentration
— happens when membrane has channels permeable to the ion and if there is a concentration gradient across the membrane

Question 26

concentration gradient

Answer 26

— difference in concentration from one region to another

— ionic concentration gradients help determine membrane potential

Question 27

concentration

Answer 27

— expressed as molars (M), the number of molecules per liter of solution
— M = mol/L
— mM = 0.001 mol/L
— for example: [NaCl] = 1mM means “The concentration of the sodium chloride solution is 1 millimolar.”

Question 28

electrical current

Answer 28

— represented by the symbol I (from french: intensité de courant, meaning “current intensity”)
— the rate of movement of electrical charge
— measured in amperes (amp)
— quantity of current determined by electrical potential and electrical conductance

Question 29

electrical potential

Answer 29

— voltage (V) aka potential difference
— the force exerted on an electrically charged particle (ion)
— reflects difference in charge between anode (+) and cathode (-)
— higher voltage = larger electrical current

Question 30

electrical conductance

Answer 30

— symbol: g
— relative ability of an electrical charge to migrate from one point to another
— inverse of resistance (R)
— SI unit: siemens (S)

Question 31

electrical resistance

Answer 31

— symbol: R
— relative inability of an electrical charge to migrate from one point to another
— inverse of conductance (g)
— SI unit: ohms (Ω)

Question 32

Ohm’s law

Answer 32

— the relationship between electrical current (I), voltage (V), and conductance (g)
— I = gV
— since g = 1/R , Ohm’s law can be expressed another way:
— I = V/R or V = IR
— Ohm’s law shows that if either conductance or potential difference is zero, no electrical current will flow

Question 33

membrane potential

Answer 33

— Vm (subscripted m)

— the voltage across a cell membrane at any given moment, measured in mV

Question 34

microelectrode

Answer 34

— probe measuring electrical activity of cells

— filled with conductive salt solution and connected to voltmeter

Question 35

voltmeter

Answer 35

— measures potential difference/electrical potential/voltage between microelectrode tip (inside cell) and wire (outside cell)

Question 36

ionic equilibrium potential

Answer 36

— the electrical potential difference (voltage) exactly balancing an ionic concentration gradient

Question 37

capacitance

Answer 37

— the ability of the membrane to store electrical charge

Question 38

ionic driving force

Answer 38

—