Communication and Hydrophobic Signals Flashcards
Multicellular organisms signal between cells using extracellular signalling molecules
In a multicellular organism, different cell types may show a tissue-specific response to the same signal.
Why cells need to communicate
Without communication, the integration and coordination of cellular activities would be impossible.
Receptor molecules
Receptor molecules of target cells are proteins with a binding site for a specific signal molecule.
Binding changes the conformation of the receptor, which initiates a response within the cell
Location of receptor proteins
Hydrophobic signalling molecules can pass through membranes, so their receptor molecules are within the cytoplasm or nucleus of the target cell.
Hydrophobic signalling molecules cannot pass though membranes so require integral cell-surface receptor proteins.
Hydrophobic signalling molecules
Hydrophobic signalling molecules can diffuse directly through the phospholipid bilayers of membranes, and so bind to intracellular receptors.
The receptors for hydrophobic signalling molecules are transcription factors.
(Transcription factors are proteins that when bound to DNA can either stimulate or inhibit initiation of transcription)
Transcription factors
Transcription factors are proteins that when bound to DNA can either stimulate or inhibit initiation of transcription
Transcription factors
Transcription factors are proteins that when bound to DNA can either stimulate or inhibit initiation of transcription
Examples of hydrophobic signalling molecules
The steroid hormones, oestrogen and testosterone are examples of hydrophobic signalling molecules.
Hormone-receptor complex
One the hormone signal has bound to the receptor, the hormone-receptor complex is formed.
The hormone-receptor complex moves to the nucleus where it binds to specific sites on DNA and affects gene expression
The hormone-receptor complex binds to specific DNA sequences called hormone-response elements (HRES)
Hormone-receptor complex
One the hormone signal has bound to the receptor, the hormone-receptor complex is formed.
The hormone-receptor complex moves to the nucleus where it binds to specific sites on DNA and affects gene expression
The hormone-receptor complex binds to specific DNA sequences called hormone-response elements (HRES)
Hormone-response elements
HRES
The hormone-receptor complex binds to specific DNA sequences called hormone-response elements (HRES)
Binding at these sites influences the rate of transcription with each steroid hormone affecting the gene expression of many different genes.
