core physiology

Question 1

what is the composition of the cell membrane?

Answer 1

Lipids - 42%
Proteins - 55%
Carbohydrates - 3%

Question 2

what are the three types of transporter proteins?

Answer 2

Carriers, Pumps and Channels

Question 3

which transporter requires ATP?

Answer 3

Pump

Question 4

name the two methods of measuring membrane potential?

Answer 4

patch clamp and glass electrode

Question 5

how would you go about using the glass electrode technique?

Answer 5

impale cell so the tip (filled with KCl) sits in the IC compartment - measure potential with respect to referee electrode

Question 6

which technique would have the most specificity

Answer 6

small electrode as much smaller with very sharp tip and insoluble thin wire

Question 7

what is the distribution of sodium

Answer 7

EC - 150 IC - 15

Question 8

what is the distribution of potassium

Answer 8

EC - 5 IC - 150

Question 9

what is the distribution of large organic anions

Answer 9

EC - 0 IC - 65

Question 10

describe the key features of Na/KATPase

Answer 10

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

Question 11

what does electrogenic mean

Answer 11

produces a change in electrical potential of cell - change in voltage plus a change in permeability of membrane

Question 12

what do K+ channels contribute to membrane potential

Answer 12

-ve charge created when K+ moves
creates driving force for K+ to move into cell
equal - opposite movement of K+ means equilibrium

Question 13

what do Na+ channels contribute

Answer 13

same as K+ - maintain equilibrium

Question 14

what does the Nernst equation calculate

Answer 14

equilibrium potential of the cell

Question 15

what is the predictive potential of Na and K

Answer 15

Na - +61.5mV K - -90.8mV

Question 16

why are the predictive values not = -70mV

Answer 16

because there must be some leakage going on meaning Na can get into the cell and K can leave

Question 17

what does the Goldman equation calculate

Answer 17

equilibrium potential of cell with more than one ion

Question 18

what is the relationship between pH and [H+]

Answer 18

increase pH doubles/halves [H+]

Question 19

how do we measure IC pH

Answer 19

using 2 microelectrodes - change in voltage = change in pH

Question 20

what are the electrodes calibrated with

Answer 20

pH standards

Question 21

what are the ideal cells for microelectrodes and why

Answer 21

nerves, muscles, Xenopus oocytes because they are large cells

Question 22

what could you use to calculate pH of small cells i.e. epithelia

Answer 22

fluorescent indicators

Question 23

how?

Answer 23

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

Question 24

what are the three factors in controlling IC pH

Answer 24

buffers
acid loading
acid extrusion

Question 25

what do buffers do

Answer 25

moderate effects of acid/alkali load by consuming/releasing protons DO NOT PREVENT CHANGE pH!!!!

Question 26

what do buffers rely on

Answer 26

COOH group and NH2 group

Question 27

what exchanger is used for acid extrusion and hoe does it act

Answer 27

Na/H exchanger protein - exchanges one Na into cell for one H out

Question 28

what does it rely on

Answer 28

Na gradient set up by Na/K pump

Question 29

does high pH inhibit or activate exchanger

Answer 29

high pH inhibits - low pH activates

Question 30

what happens when allosteric modification occurs

Answer 30

a unused proton binds the the allosteric site increasing activity

Question 31

what is NHE1

Answer 31

housekeeping function with a primary role of regulating pH

Question 32

what inhibits NHE1

Answer 32

low conc of amiloride plus its analogue EIPA

Question 33

where is NHE1 found

Answer 33

basolateral membrane of epithelial cells

Question 34

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

Answer 34

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

Question 35

is it inhibited by high or low pH

Answer 35

inhibited at low pH and activated at high`

Question 36

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

Answer 36

the anion exchanger family (AE) - 4 subtypes

Question 37

what are they all inhibited by

Answer 37

DIDS

Question 38

do these exchangers rely on Na gradient

Answer 38

no they are independent of Na conc

Question 39

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

Answer 39

RBCs but also in kidneys - hamburger shift/chloride shift

Question 40

when is there no net proton flux

Answer 40

Je = Jl

Question 41

why is important to control IC Na+ - epithelial cells

Answer 41

creates gradients that allow uptake of other molecules

Question 42

excitable cells?

Answer 42

need high chemical gradient to create action potentials

Question 43

what is Na/K pump inhibited by

Answer 43

glucosides such as ouabain and digoxin

Question 44

what does Na/K pump do

Answer 44

maintains low IC Na snd high IC K

Question 45

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

Answer 45

electrogenic | accumulation of K inside cell -MAJOR FACTOR

Question 46

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

Answer 46

requires ALOT of energy

Question 47

what are normal compositions of Ca

Answer 47

EC - 1mM IC - 100nM

Question 48

why is Ca regulation important

Answer 48

important secondary messenger in important signalling pathways

Question 49

what are the two mechanisms in keeping low IC Ca

Answer 49

Na/Ca exchanger | Ca ATPase

Question 50

describe Na/Ca exchanger

Answer 50

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

Question 51

what family is Na/Ca exchanger

Answer 51

SLC8 family in mammals 3 forms exist

Question 52

what family is Ca ATPase

Answer 52

P-type ATPase family

Question 53

describe each type of Ca pump

Answer 53

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

Question 54

what are the 4 mechanisms of Ca signalling

Answer 54

VOCC ROCC MACC SOCC

Question 55

VOCC

Answer 55

voltage operated calcium channel found in excitable cells activated by depolarisation

Question 56

ROCC

Answer 56

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

Question 57

MACC

Answer 57

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

Question 58

SOCC

Answer 58

store operated calcium channel | activated following depletion in Ca stores

Question 59

what are the two store pathways

Answer 59

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