Biology, Eighth Edition (Raven)

Chapter 46: The Endocrine System

Intracellular Receptor Model

How does the structure of a signal molecule determine its function? Signal molecules can interact with either intracellular or extracellular receptors. For a signal molecule to bind with an intracellular receptor it must be able to pass through the cellular membrane. Generally signal molecules that enter the cell are nonpolar and fat soluble. These signal molecules can pass through the lipid bilayer of the cell membrane. Signals that bind with extracellular receptors are proteins or other types of molecules that cannot readily pass through the membrane.

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


Lipid soluble hormones...
A)require a membrane receptor protein to enter the cell.
B)diffuse through the cell membrane.
C)enter the cell through active transport.
D)work as ligands on the surface of the cell membrane.
E)require specific gates to pass through the cell membrane.

Once inside of the cell, these lipid soluble hormones...
A)bind with a DNA molecule.
B)bind with a specific receptor molecule inside the nucleus.
C)bind with a mRNA molecule.
D)bind with a specific receptor molecule inside the cytoplasm.
E)bind with a ribosome.

As a result...
A)the DNA-hormone complex produces mRNA molecules.
B)the receptor-hormone complex binds with a mRNA molecule to produce a DNA molecule.
C)the hormone-mRNA complex enters the cytoplasm and produces proteins.
D)the receptor-hormone complex binds with a DNA molecule to produce a mRNA molecule.
E)the hormone-ribosome complex produce proteins.

The ultimate result of lipid-soluble hormones on cells is the production of proteins.

The mRNA molecule moves from the cytoplasm to the nucleus and binds to a ribosome where it directs the synthesis of specific proteins.
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