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BMS242- Physiology and Pharmacology > core physiology > Flashcards

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

what happens when allosteric modification occurs

a unused proton binds the the allosteric site increasing activity

31

what is NHE1

housekeeping function with a primary role of regulating pH

32

what inhibits NHE1

low conc of amiloride plus its analogue EIPA

33

where is NHE1 found

basolateral membrane of epithelial cells

34

what exchanger is involved in acid loading and what does it do

Cl/HCO3 exchanger - 1 Cl in and 1 HCO3 out

35

is it inhibited by high or low pH

inhibited at low pH and activated at high`

36

what family does this exchanger belong to and how many subtypes are there

the anion exchanger family (AE) - 4 subtypes

37

what are they all inhibited by

DIDS

38

do these exchangers rely on Na gradient

no they are independent of Na conc

39

where is AE1 predominantly found and what shift is it responsible for

RBCs but also in kidneys - hamburger shift/chloride shift

40

when is there no net proton flux

Je = Jl

41

why is important to control IC Na+ - epithelial cells

creates gradients that allow uptake of other molecules

42

excitable cells?

need high chemical gradient to create action potentials

43

what is Na/K pump inhibited by

glucosides such as ouabain and digoxin

44

what does Na/K pump do

maintains low IC Na snd high IC K

45

what are the two roles Na/K pump has in membrane potential

electrogenic
accumulation of K inside cell -MAJOR FACTOR

46

why is Na/K pump only found in physiologically significant pathways such as collecting duct and excitable cells

requires ALOT of energy

47

what are normal compositions of Ca

EC - 1mM IC - 100nM

48

why is Ca regulation important

important secondary messenger in important signalling pathways

49

what are the two mechanisms in keeping low IC Ca

Na/Ca exchanger
Ca ATPase

50

describe Na/Ca exchanger

usually exchanges EC Na for IC Ca
stoichiometry means effect of Na influx is magnified as 3Na:1Ca

51

what family is Na/Ca exchanger

SLC8 family in mammals 3 forms exist

52

what family is Ca ATPase

P-type ATPase family

53

describe each type of Ca pump

PMCA - plasma membrane Ca pump - Ca out of cell
SERC - smooth endoplasmic reticulum Ca pump - pumps Ca into organelles for storage
SPCA - Golgi Ca pump - also transports Mn

54

what are the 4 mechanisms of Ca signalling

VOCC
ROCC
MACC
SOCC

55

VOCC

voltage operated calcium channel
found in excitable cells
activated by depolarisation

56

ROCC

receptor operated calcium channel
found in secretory cells + synapses
activated by agonist binding e.g. NMDA

57

MACC

mechanically activated calcium channel
stretch activated
found in cells that respond to deformation

58

SOCC

store operated calcium channel
activated following depletion in Ca stores

59

what are the two store pathways

IP3 receptors activate channel - ubiquitous
ryanodine receptors - low conc activates channel - high inhibits - also activated by caffiene - usually only in excitable cells