A) Depolarization C) Blood-brain barrier
B) Potassium spatial buffering D) Goldman equation
Ans: B
Difficulty: Moderate

12. Distinguish between the “head” and “tail” of phospholipids. Choose the correct option.
A) The phospholipids have a nonpolar “head” and polar “tail.”
B) The phospholipids “head” contains hydrophilic phosphate and “tail” contains a hydrophobic hydrocarbon.
C) The phospholipid “head” is hydrophobic and the hydrocarbon “tail” is hydrophilic.
D) The phospholipid “heads” face each other and “tails” face the watery extracellular and intracellular environments.
Ans: B
Difficulty: Easy

13. In which condition do astrocytes take up extracellular K+? Choose the correct option.
A) Rise in extracellular potassium concentrations
B) Fall in extracellular potassium concentrations
C) Potassium equilibrium potential
D) All of the above
Ans: A
Difficulty: Difficult

14. Which of the following factors determines the ion selectivity of specific ion channels? Choose the correct option.
A) Number of protein molecules assembling to form a pore
B) Number of ion channels in the membrane
C) Nature of the R groups lining the ion channel
D) Gating properties
Ans: C
Difficulty: Easy

15. Two types of cells have excitable membranes, neurons and muscle cells.
Ans: True
Difficulty: Easy

16. Protein shape influences protein function.
Ans: True
Difficulty: Easy

17. Peptide bonds are a single chain of amino acids.
Ans: False
Difficulty: Easy

18. The differences between amino acids result from the differences in the size and nature of the R groups.
Ans: True
Difficulty: Easy

19. The subunits of different potassium channels have common structural features that bestow selectivity for K+ ions. ______________ is one such structural feature.
Ans: Pore loop
Difficulty: Easy

20. All amino acids have a central _________ atom.
Ans: Alpha carbon
Difficulty: Easy

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