Biology, Eighth Edition (Raven)

Chapter 41: Sensory Systems in Plants

How Intracellular Receptors Regulate Gene Transcription

What is the difference between inhibitor and activator proteins? Gene transcription is controlled by multiple factors. Some proteins bind to DNA sequences and start the process of gene transcription. RNA synthesis can only occur when these activators are bound to specific DNA sequences. Inhibitors are other molecules that prevent transcription from occurring. Inhibitors bind to activator molecules and prevent them from binding to DNA. A molecular signal is necessary to remove the inhibitor molecule from the activator and allow transcription to proceed.

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


1.	Which of the following cell signaling molecules crosses the cell membrane the easiest?

		A)	molecules that are small and lipid-insoluble
		B)	molecules that are small and lipid-soluble
		C)	molecules that are small and water-soluble
		D)	molecules that are large and water-soluble
		E)	molecules that are large and lipid-insoluble

2.	Intracellular receptors usually contain binding sites for

		A)	signaling molecules only.
		B)	DNA only.
		C)	both DNA and signaling molecules.
		D)	either DNA or signaling molecules.
		E)	neither DNA nor signaling molecules.

3.	Intracellular receptors may be found

		A)	in the cytoplasm only.
		B)	in the nucleus only.
		C)	either in the cytoplasm or the nucleus.
		D)	either in the cytoplasm or on the cell membrane.
		E)	either in the nucleus or on the cell membrane.

4.	The response of the target cell to the signal is the same regardless of the type of signal.

		A)	True
		B)	False

5.	Intracellular receptors bind to specific nucleotide sequences.

		A)	True
		B)	False