CBG 30

Question 1

Inward current?

Answer 1

becomes more +: more + in or - ions out

Question 2

what is outward current?

Answer 2

less positive: more - in or + ions out

Question 3

What is the inside membrane resting potential?

Answer 3

-70mV

Question 4

what are the equilibrium potentials of NA+,K+ and Cl-?

Answer 4

+40

• 100
• 60

Question 5

what is reversal potential teh same as?

Answer 5

equilibrium potential

Question 6

define depolarisation,repolarisation and hyperpolarisation?

Answer 6

Depolarisation-the membrane potential becomes less negative, occurs when sodium channels open and Na+ ions enter the cell.

reploarisation-return of membrane towards resting potential of cell. Na channels close .In addition, additional potassium channels open allowing K+ ions to exit the cell.

hyperpolarisation- overshoot and membrane become more -ve.The additional K channels stay open even when the membrane potential reaches the resting level. So, the potential goes even more negative than resting

Question 7

what is the rearranged Nernst equation? (logged)

Answer 7

E=0.058/z log [X]1/[X}2

Question 8

why does internal calcium levels have to be kept low?

Answer 8

interfer with signalling otherwise

Question 9

what is electric charge (Q) measured in?

Answer 9

C coulombs

Question 10

What is voltage and what is it measured in?

Answer 10

electromotive force EMV /electric potential between 2 points expressed in V ie resting potential

Question 11

What does ohms law state?

Answer 11

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

Question 12

what is the flow of charge ?what direction is flow?

Answer 12

Current (I) measured in amperes A. flow is direction positive charge moves

Question 13

what is resistence, what is it measured in and what is a biological example?

Answer 13

property that hinders flow of current and measured in ohms.

plasma membrane with ion channels closed (high resistance) and when open (low resistance)

Question 14

what is the difference between capacitance and conductance?

Answer 14

conductance (G) is the recipricol of resistence and is measured in siemens (s)

capacitance is the property of a non conductor to store electric charge. measured in farads. ie plasma membrane stores electricsal charge because of all the charged proteins and potential difference between outside and inside.

Question 15

I

Answer 15

current

Question 16

ohms

Answer 16

measurement of resistance

Question 17

G

Answer 17

conductance measured in siemens S

Question 18

S

Answer 18

measure of conductance

Question 19

C

Answer 19

capacitance (farads)

Question 20

farads

Answer 20

measurement of capacitance

Question 21

V=IR

Answer 21

ohms law

Question 22

V or E

Answer 22

voltage measured in V

Question 23

Q

Answer 23

electric charge measured in C coulombs

Question 24

farads

Answer 24

measurement of capacitance

Question 25

usually ratio of Na/K+ pumped in /out?

Answer 25

3 Na+ out

2 K+ in

Question 26

why does the membrane have a capacitance?

Answer 26

lipid core is an insulator and it can store charge.

Question 27

what i the ion channel in the circuit analogy?

Answer 27

a resistor

Question 28

what does the membranes ionic conductance depend on?

Answer 28

presence of open ion channels

Question 29

T or F there is lots of membrane negativity in the neighbourhood of the membrane?

Answer 29

false. there is mostly electrical neutrality in the neighborhood of the membrane.

Question 30

why is there mostly electrical neutrality in membrane neighborhood?

Answer 30

cell membrane separates charges with cations and anions forming a diffuse layer on opposite sides of the mebrane. charges are held in a narrow thin region due to electrostatic interactions but the bulk solution on either membrane side is electronically neutral.

Question 31

uniporter

Answer 31

transports single ion in one direction

Question 32

symporter

Answer 32

transports 2 ions in the same directioj

Question 33

antiporter

Answer 33

transports 2 ions in opposite directions

Question 34

what is an example of an antiporter?

Answer 34

Na+/ca2+ which uses force of Na+ flowing in cell to transport Cl AGAINST conc gradient OUT of the cell (ca interferes with signalling)

Question 35

what are said to be rheogenic and why?

Answer 35

ionic pumps that produce a net charge.

they produce a transmembrane electric current

Question 36

what is said to be electrogenic?

Answer 36

the pump if its current produces a large effcect on the voltage across the membrane

Question 37

cardiac glycoside ouabain?

Answer 37

a drug that blocks NA+/K+ ATPase by competing for K+ binding site. (inhibits active transport)

Question 38

what blocks NA+/K+ ATPase by competing for K+ binding site?

Answer 38

cardiac glycoside oubain

Question 39

what does the ATPase in the na/k pump have wrt aa types?

Answer 39

501 LYSINE

369 ASPARTATE

Question 40

where does the enmergy for active transport come from?

Answer 40

hyrolysis of ATP by ATPases present in the membrane

Question 41

what is the Na+/k+ radient the pump has to work against?

Answer 41

10:1 gradient

Question 42

what does cyanide do?

Answer 42

prevents production of ATP–> brings active transport to a halt

Question 43

does NA+/K+ ATPase transport Li+?

Answer 43

no,active transport systems exhibit a high degree of selectivity (despite Li+ having similar characteristics of Na+)

Question 44

Briefly describe the basic action of the 3Na+/2K+ ATPase pump?

Answer 44

1) transporter binds 3Na+ from cytosol
2) phosphorylation by ATP favours conformational change allowing Na+ to be released
3) Na+ is released and K+ binds
4) dephosphorylation favours original conformation
5) K+ is released to cytosol and cycle can repeat