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Question 18M.2.HL.TZ1.6b

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Date May 2018 Marks available [Maximum mark: 4] Reference code 18M.2.HL.TZ1.6b
Level HL Paper 2 Time zone TZ1
Command term Outline Question number b Adapted from N/A
b.
[Maximum mark: 4]
18M.2.HL.TZ1.6b
(b)

Outline how neurons generate a resting potential.

[4]

Markscheme

a. sodium-potassium pump 

b. sodium /Na+ out and potassium /K+ in 
OR
sodium/Na+ concentration higher outside and potassium/K+ higher inside 

c. three Na+ pumped for every two K+ (hence negative inside) 
OR
inside of axon holds negative ions/Cl- ions/negatively charged proteins/organic anions (hence negative inside) 

d. by active transport / using ATP 

e. inside (of axon/neuron) is negative in comparison to outside 
OR
electrochemical concentration/charge difference (across the membrane) is the resting potential 

f. resting potential is –70 mV

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