Signal Transduction Flashcards
Quorum sensing
A concentration of signaling molecules allows bacteria to sense local population density
Cell junctions
Local signaling by direct contact. Both animals and plants have cell jucntions that allow molecules, including signaling molecues, to pass readily between adjacent cells without crossing plasma membrane.
Cell-cell recognition
Local signaling by direct contact. Two cells in an animal may communicate by interaction between transmembrane proteins protruding from their surfaces, sending info bidirectionally.
Paracrine signaling
Local signaling but no direct contact. A signaling cell acts on nearby target cells by secreting molecules of a local regulator. Fairly quick, go a short distance.
Synaptic signaling
A type of paracrine signaling. A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell. Fairly quick, go a short distance once released by axons.
Autocrine signaling
The secreting cell sends something out and binds back to the secreting cell. This binding sets up a signal transduction pathway.
Endocrine (hormonal) signaling
Long-distance signaling. Specialized endocrine cells secrete hormones into body fluids, often blood. Hormones reach most body cells, but are bound by and affect only some cells.
Two types of signaling molecules:
Nonpolar- can travel right through the cells membrane & find its target receptor inside the cell i.e steroids
Polar- cannot travel across the plasma membrane, so they find their embedded in the membrane i.e polypeptides, aa derivatives
4 main types of receptors:
1) intracellular receptors- these may be located in the cytoplasm or the nucleus
2) Ion channel receptors- the receptors of neurotransmitters are often ion channels. Ions can’t go through pm easily without channels.
3) G-protein linked receptor
4) Protein kinase receptors (RPK)
Signal Transduction Pathway
The process by which a signal on a cell’s surface is converted to a specific cellular response in a series of steps.
Reception- the target cell detects a signaling molecules that binds to a receptor protein on the cell surface.
Transduction- the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway. Receptor interacts with protein 1 changing its conformation to interact with protein 2.
Response- the transduced signal triggers specific response in a target cell.
G-protein coupled receptors
cell surface transmembrane receptors that work with the help of a G-protein. Many of them are 7 transmembrane in form, meaning that their polypeptide goes across the membrane 7 times.
What triggers G-protein to switch from GDP to GTP?
It’s interaction with the G-protein coupled receptor. Binding of a ligand to GCPR changes it shapes and allows it to contact G protein. G-protein then releases bound GDP & binds free GTP.
Cyclic AMP (cAMP)
The adenyl cyclase chops off the last two phosphates & are released as pyrophosphates. The remaining phosphate connects to the 3’ carbon.
Can cAMP be around forever?
No, there’s a series of enzymes that can break it down. . Such as phosphodiesterase which breaks the connection of the 3’ carbon to the phosphate returning it to AMP.
What is a main target of cAMP?
Protein Kinase A
