18.10Suppose that for every Na+transported from the inside to the exterior one K+is transported
from the exterior to the interior. The voltage is 60 mV higher in the interior. The interior
concentrations are 100 mM for K+and 150 mM for Na+and the exterior concentrations
are 2 mM for K+and 1 mM for Na+. Calculate the molar free-energy difference for each
process and the net transport process.
18.11 What is the biological role of transporters?
18.12 What is the alternating-access model of transporters?
18.13 What is a proposed role for short αhelices in the Na+/H+antiporter function?
18.14 What factors are proposed to control water flow in aquaporin?
18.15 Discuss briefly the similarities and differences between voltage-gated channels and
nonvoltage-gated channels.
18.16 Compare and contrast voltage-gated potassium channels and the KcsA channel.
18.17 What is a ligand-gated channel?
18.18What structural changes are proposed to induce channel gating in mechanosensitive channels?
18.19 How do electrostatics contribute to the ion flow?
18.20 What is the role of the large cavity at the entrance for ions in the potassium channel?
18.21 Explain how ion channels distinguish between Na+and K+.
18.22 How can a FRET experiment be used to identify the voltage-induced structural changes
of a voltage-gated ion channel?
18.23 Summarize the known structural properties of the acetylcholine receptor.
singke
(singke)
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