Flashcards in core physiology Deck (59)
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1
what is the composition of the cell membrane?
Lipids - 42%
Proteins - 55%
Carbohydrates - 3%
2
what are the three types of transporter proteins?
Carriers, Pumps and Channels
3
which transporter requires ATP?
Pump
4
name the two methods of measuring membrane potential?
patch clamp and glass electrode
5
how would you go about using the glass electrode technique?
impale cell so the tip (filled with KCl) sits in the IC compartment - measure potential with respect to referee electrode
6
which technique would have the most specificity
small electrode as much smaller with very sharp tip and insoluble thin wire
7
what is the distribution of sodium
EC - 150 IC - 15
8
what is the distribution of potassium
EC - 5 IC - 150
9
what is the distribution of large organic anions
EC - 0 IC - 65
10
describe the key features of Na/KATPase
contributes 20% directly
electrogenic - 3 Na out, 2 K in - therefore lose 1 positive charge each time
indirect IC Na and K maintained
if blocked - instantly wipes out membrane potential
11
what does electrogenic mean
produces a change in electrical potential of cell - change in voltage plus a change in permeability of membrane
12
what do K+ channels contribute to membrane potential
-ve charge created when K+ moves
creates driving force for K+ to move into cell
equal - opposite movement of K+ means equilibrium
13
what do Na+ channels contribute
same as K+ - maintain equilibrium
14
what does the Nernst equation calculate
equilibrium potential of the cell
15
what is the predictive potential of Na and K
Na - +61.5mV K - -90.8mV
16
why are the predictive values not = -70mV
because there must be some leakage going on meaning Na can get into the cell and K can leave
17
what does the Goldman equation calculate
equilibrium potential of cell with more than one ion
18
what is the relationship between pH and [H+]
increase pH doubles/halves [H+]
19
how do we measure IC pH
using 2 microelectrodes - change in voltage = change in pH
20
what are the electrodes calibrated with
pH standards
21
what are the ideal cells for microelectrodes and why
nerves, muscles, Xenopus oocytes because they are large cells
22
what could you use to calculate pH of small cells i.e. epithelia
fluorescent indicators
23
how?
load cells with inactive form (so it can pass through the membrane)
inside cell it is converted to active form
excites a light with specific wavelength - amount at 2nd wavelength is measures
fluorescence = IC pH
indicator is calibrated inside cell and membrane is permeabilised and pH of bath solution is changed
24
what are the three factors in controlling IC pH
buffers
acid loading
acid extrusion
25
what do buffers do
moderate effects of acid/alkali load by consuming/releasing protons
DO NOT PREVENT CHANGE pH!!!!
26
what do buffers rely on
COOH group and NH2 group
27
what exchanger is used for acid extrusion and hoe does it act
Na/H exchanger protein - exchanges one Na into cell for one H out
28
what does it rely on
Na gradient set up by Na/K pump
29
does high pH inhibit or activate exchanger
high pH inhibits - low pH activates
30
