UNIT 1 EXTRACELLULAR SIGNALLING Flashcards
What are the two principal forms of communication in multicellular organisms?
Hormonal and nervous.
WHat happens with extracellilar signalling molecules?
one cell releases a chemical signal that another cell recieves and responds to.
Define extracellular signalling molecules.
Signalling molecules that originate from outside the target cell.
What are hormones and how do they travel around the organism?
Extracellular signalling molecule secreted by one tissue into the blood, circulates in the blood stream.
What are the two types of hormones? Give some examples.
Hydrophillic (peptide hormones: insulin, ADH, growth hormone)
Hydrophobic (steroid hormones:testosterone)
What are the extracellular signalling molecules released during nervous communication called? Are they hydrophobic or hydrophillic?
Neurotransmitters. Hydrophillic.
What is the main difference between neurotransmitter and hormones?
Neurotransmitters are much more specific due to the intimate association between signalling and target cell.
How does an extracellular signalling molecule cause an effect?
By binding to its specific target RECEPTOR molecule.
What is the receptor molecule for hydrophillic signalling molecules found?
On the membrane. They are integral proteins.
Where is the receptor for hydrophobic signalling molecules?
Within the cytoplasm or the nucleus of the target cell. (They are lipid soluble so can pass through the cell membrane).
What is the target cell for a steroid hormone?
gene-regulatory protein which changes conformation. This leads it to binding directly to the DNA and regulating the transcription of specific genes.
What is the name of the process that allows hydrophilic signalling molecules to pass signals to other cells?
Signal transduction.
What does signal transduction involve?
A hydrophilic signalling molecule bind to a transmembrane protein and causes in it to alter in some way. The change in the protein causes a change in the cells behaviour (eg may release a secondary messenger molecule into cytoplasm which activates proteins by phosphorylation) .
How can hormones be highly specific?
Only target cells have the required receptor protein on their membrane.
Give two examples of neurotransmitters.
Acetylcholine and noradrenalin. Hydrophillic peptides.
