KA5 - Communication within Multicellular Organisms Flashcards
How do multicellular organisms achieve coordination?
Through extracellular signalling molecules, receptors and responses
What are receptor molecules of target cells?
Proteins with a binding site for a specific signal molecule
What does binding change?
The conformation of the receptor and this can alter the response of the cell
Different cell types produce specific signals which can…
Only be detected and responded to by cells with the specific receptor
In a multicellular organism, different cell types may show… ?
A tissue specific response to the same signal
What do hydrophobic signalling molecules include?
The thyroid hormone thyroxine and steroid hormones
What can hydrophobic signalling molecules influence?
Directly influence transcription of genes
Hydrophobic signalling molecules can diffuse through…?
Membranes so their receptor molecules can be within the nucleus
What are the receptor proteins for steroid hormones known as?
Transcription factors
Only once the hormone signal has bound to the receptor can… happen?
The transcription factor bind to gene regulatory sequences of DNA for transcription to occur
What do hydrophilic signalling molecules include?
Peptide hormones and neurotransmitters
What do hydrophilic signals require?
Receptor molecules to be at the membrane of the cell
When do transmembrane receptors change conformation? What happens?
When the ligand binds on the cell surface;
The signal molecule does not enter the cell but the signal is transduced across the membrane of the cell
What do transduced hydrophilic signals often involve?
Cascades of G-proteins or phosphorylation by kinase enzymes
How can the type 1 diabetes be caused?
By failure to produce insulin
How can type 2 diabetes be caused?
Loss of receptor function
What is type 2 diabetes generally associated with? How can this be helped?
Generally associated with obesity
Exercise also triggers recruitment of GLUT4 so can improve uptake if glucose to fat and muscle cells in subject with type 2
Binding of peptide hormone ADH to its receptor in collecting duct of kidney triggers…?
Recruitment of channel protein aquaporin 2 (AQP2)
What do aquaporins provide?
A highly efficient route for water to move across membranes
What does recruitment of AQP2 allow for?
Control of water balance in terrestrial vertebrates
What does failure to produce ADH or insensitivity of its receptor result it?
Diabetes insipidus
What does binding of the peptide hormone insulin to its receptor trigger?
Recruitment of GLUT4 glucose transporter to the cell membrane of fat and muscle cells
When do thyroid hormone receptor protein bind to DNA? What does it do?
In the absence of thyroxine and inhibits transcription of the gene for Na/KATPASE
When thyroxine binds to the receptor protein what happens?
Conformational change prevents protein binding to the DNA and transcription of the gene for Na/KATPase can begin raising metabolic rate
