CBG30 Flashcards by Hazel Cooley

What are the internal and external concentrations of the main electrolytes in a typical muscle tissues?

electrolyte interior exterior (mM)
Na+ 10 120
K+ 140 2.5
Ca2+ 10^-3 2
Cl- 3-4 120
A- 140
A- molar equivalent of negative charges carried by other molecules

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what is the inside resting potential?

-70mV as permeable to both K+ and Na+

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What is the inward current?

becomes more positive, movement of positive ions

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What is the outward current?

becomes more negative, movement of negative ions

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What are the equilibrium potentials fro NA+, K+ and Cl-

Na+ +40
K+ -100
Cl- -60

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Define depolarise

more positive

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define hyperpolarise

more negative

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What is synaptic current carried by at the vertebrate neuromuscular junction?

Na+ and K+
currents at different potentials
channel is equally permeable to both so size of 1K and 1Na depend upon the driving force for each ion.

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What happens at E rev net current?

E- rev = reversal potentail = equilibirum potential = resting potential
E rev net current = 0

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What happens when Vm= ENa

+40
inward current
k leaves the cell

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What happens when ENa > Vm > Erev

+40 > Vm >-70

more K+ leave than Na+ enter

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What happens when Vm = Erev

-70
equilbirum
more Na+ entering than K+ leaving

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What happens when Erev>Vm>Ek

-70> Vm > -100

more Na+ entering than K+ leaving

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What happens at Vm=Ek

-100

Na+ enters the cell

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What is the Nernst equation?

E=Rt/zF ln [X1]/[X2]
E= potential difference between the 2 compartments in voltz
R= Gas Constant
= 8.314 J deg-1 mol-1
T= absolute temperature
[X]1 and [X]2 are molar concentrations in compartment 1 and 2 respectively
z= charge on ion
F= faradays constant

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What is the reversal potential?

equilbrium potetnial/ resting potential

What is Q

electrical charge of an ion

measured in coloumbs

What is V/E

electromotive force EMF or electrical potential

measured in volts

What is I

current
flow of charge
measured in amperes
ussually measured in direction of the positive ion

What is R

resistance
hinders how current can be measured
in ohms

What is G

conductance
recipricol of resistance
(1/R)
measured in siemans (S)

What is C

capacitance
property of non confuctor to store electric charge
measured in farads
eg. plasma membrane stores charge due to potential difference between in and out

what is ohms law?

current is proportional to voltage and inversely proportional to resistance
V= IR

What can passive electircal properties of a cell membrane be represented by?

a simple electrical circuit
has capacitance as lipid core is an insulator
conductance depends on the presence of open ion channel - ion channels - resistor

What does the cell membrane act as?

capacitor can separate charges cations and anions form a diffuse layer on opposite sides of the membrane = electrostatic interaction holds charge in narrow region immediately adjacent to the 2 surfaces of cell membrane- apart from these excess cations/anions either side of membrane conforms to neutrality.

What can flow of electrons be compared to?

flow of water in a pipe | resistance analagous to restriction in pipe

What is a uniporter?

transport single ion in a single direction

what is a symporter

transport to ions in same direction

what is an antipoter

exchange 2 ions in opposite directions eg. Na+/Ca+ uses force of Na+ flowing in cell to transport Ca2+ against electrochemical gradient oout of cell - Ca2+ Ca2+ = signalling molecule= low levels

Describe the sodium potassium pump

major expenditure in cell - metabolic requirement when open to inside of the cel= 3 binding sites for Na+ binding causes conformational change in proteins via phosphorylation of ATP pore region now open to exterior - conformation allows relase of Na+ opens up binding site for 2K+ dephosphorylation favours original conformation of ATPase K+ is released into cytosol repeat``

What do active transport systems exhibit a high degree of? example

selectivity | eg. Li+ has similar ion character to Na+ but not transported by i

What inhibits ATP production?

cyanide

what are ionic pumps that produce a net charge said to be?

rheogenic because they produce a transmembrane electirc current

when is an ionic pump said to be electrogenic?

qhwn a current produces a measurable effect of voltage across membrane

What can active transport be selectively inhibited by? | example

drugs | eg. cardiac glycoside ouabain blocks Na+K+ ATPase by competeing for K+ binding site.

What kind of kinetics does ATPase display?

michealas menton and competitive inhibnition by analog molecules