Biology, Eighth Edition (Raven)

Chapter 5: Membranes

Receptors Linked to a Channel Protein

Why are channels through membranes so important for nerve and muscle function? Both nerves and muscles rely on the rapid transmission of information and of signals for movement. The diffusion of chemical signals over any significant distance would be too slow to cause muscle contractions quickly enough to deal with the challenges of moving a large body in a complex environment. Electrical signals travel much more rapidly and the direction of the signal can be more easily controlled. The mechanism for generating and controlling electrical signals is the movement of charged material (ions) across cellular membranes in a limited area. The control of ion movement requires gated channels through the membrane that are specific for certain ions and either open or close (depending on the ion) in response to a change in electrical charge.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

When the acetylcholine receptor sites are not occupied...
A)a ligand is formed.
B)the sodium channels open.
C)the sodium channels remain closed.
D)sodium ions diffuse through and enter the cell.
E)sodium ions diffuse through and leave the cell.
2.

When the acetylcholine binds to the receptor sites...
A)a ligand is formed.
B)the sodium channels open.
C)the sodium channels remain closed.
D)sodium ions diffuse through and enter the cell.
E)sodium ions diffuse through and leave the cell.
3.

Which causes...
A)a ligand to be formed.
B)the sodium channels to open.
C)the sodium channels close.
D)sodium ions to diffuse through and enter the cell.
E)sodium ions to diffuse through and leave the cell.
4.

The sodium channels in the cell membrane have receptor sites for acetylcholine.
A)True
B)False
5.

This channel is formed by a channel protein.
A)True
B)False
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