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CBG > CBG30 > Flashcards

CBG30 Flashcards

1
Q

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

A

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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2
Q

what is the inside resting potential?

A

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

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3
Q

What is the inward current?

A

becomes more positive, movement of positive ions

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4
Q

What is the outward current?

A

becomes more negative, movement of negative ions

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5
Q

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

A

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

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6
Q

Define depolarise

A

more positive

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7
Q

define hyperpolarise

A

more negative

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8
Q

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

A

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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9
Q

What happens at E rev net current?

A

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

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10
Q

What happens when Vm= ENa

A

+40
inward current
k leaves the cell

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11
Q

What happens when ENa > Vm > Erev

A

+40 > Vm >-70

more K+ leave than Na+ enter

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12
Q

What happens when Vm = Erev

A

-70
equilbirum
more Na+ entering than K+ leaving

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13
Q

What happens when Erev>Vm>Ek

A

-70> Vm > -100

more Na+ entering than K+ leaving

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14
Q

What happens at Vm=Ek

A

-100

Na+ enters the cell

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15
Q

What is the Nernst equation?

A 
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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16
Q

What is the reversal potential?

A

equilbrium potetnial/ resting potential

17
Q

What is Q

A

electrical charge of an ion

measured in coloumbs

18
Q

What is V/E

A

electromotive force EMF or electrical potential

measured in volts

19
Q

What is I

A

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

20
Q

What is R

A

resistance
hinders how current can be measured
in ohms

21
Q

What is G

A

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

22
Q

What is C

A

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

23
Q

what is ohms law?

A

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

24
Q

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

A

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

25
Q

What does the cell membrane act as?

A

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.

26
Q

What can flow of electrons be compared to?

A

flow of water in a pipe

resistance analagous to restriction in pipe

27
Q

What is a uniporter?

A

transport single ion in a single direction

28
Q

what is a symporter

A

transport to ions in same direction

29
Q

what is an antipoter

A

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

30
Q

Describe the sodium potassium pump

A

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``

31
Q

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

A

selectivity

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

32
Q

What inhibits ATP production?

A

cyanide

33
Q

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

A

rheogenic because they produce a transmembrane electirc current

34
Q

when is an ionic pump said to be electrogenic?

A

qhwn a current produces a measurable effect of voltage across membrane

35
Q

What can active transport be selectively inhibited by?

example

A

drugs

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

36
Q

What kind of kinetics does ATPase display?

A

michealas menton and competitive inhibnition by analog molecules

CBG (19 decks)

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