Lecture 2 Flashcards
What are the 3 points of cell signalling
To receive signal, to transduce the signal and to respond to the signal
What are the 6 steps of cell signalling
Synthesis of signalling molecule, release of signalling molecule, transport of signalling molecule to target cell, detection of the signal by target cell/reception, response by target cell and finally feedback to the original signalling cell
What are the 3 ways to guarantee specificity of signalling
Direct contact, selective receptor expression and degradation or uptake of signal molecule
What are the 4 modes of signalling
Juxtacrine, autocrine, paracrine and endocrine
Describe type 1 juxtacrine signalling
Direct cell to cell contact. Mediated by gap junctions which are composed of connexin proteins, this allows very rapid communication between cells, bi-directional transport of small molecules and ions and electrical and chemical coupling between cells.
Describe type 2 juxtacrine signalling
Involves a receptor. A signalling molecule is produced but not released as it is membrane bound and the receptor of the receiving cell is in direct contact with the signalling molecule. Used to deliver more complex information such as when in development. This signalling is referred to as the notch pathway
Describe autocrine signalling
Signalling between close proximity cells of the same type. Involves a release and reception of signal molecule and can be used to coordinate activity between groups of similar cells if cells are both signalling and receiving. Specificity is achieved by receptor specificity and rapid degradation of the signalling molecule
Describe paracrine signalling
Local signalling between 2 different cell types, requires release and reception of signalling molecule. Specificity is achieved by receptor specificity and rapid degradation of the signalling molecule
Neuronal signalling is what
An example of autocrine and/or paracrine signalling but the signalling molecules are neurotransmitters released from neurons and specialised highly localised synaptic sites. Rapid but short lasting in effect. Specificity is achieved by precise contacts and rapid removal of the neurotransmitter
Describe endocrine signalling
Long distance signalling, with hormones carried through the blood that were produced in the endocrine glands, tissues and cells. The signal MUST NOT degrade as it may not reach its destination. Specificity by receptors
What are the 3 categories of common ligands and an example of each
Hormones eg. testosterone. Growth Factors eg. Cytokines. Neurotransmitters eg. acetylcholine
What are the 3 classes of extracellular receptors and what do they do
Ion channels, GPCR and enzyme linked receptors. They change membrane conductance, alter protein activity and regulate cellular events
What are the 2 types of second messengers
Membrane associated and located in the cytosol
What is role of protein kinases
Activation of proteins during signalling cascades. They selectively modify the proteins, add phosphates to the amino acids on the protein to cause a confirmational change.
Most common Post translational modification
Phosphorylation. Regulated addition of a phosphate which will activate proteins. This phosphate adds a large negative charge to the protein allowing for a confirmational change to take place, activating the protein
How does phosphorylation work
Phosphates are transferred from ATP(turning it into ADP) onto the amino acids on the target protein. Protein kinases are the ones that carry this process out, while protein phosphatases remove the phosphates later on
